Remove GnomeCanvas dependency.

git-svn-id: http://svn.drobilla.net/lad/trunk/ganv@3842 a436a847-0d15-0410-975c-d299462d15a1

1 files changed, 3820 insertions, 0 deletions

diff --git a/src/canvas-base.c b/src/canvas-base.c
new file mode 100644
index 0000000..2cff987
--- /dev/null
+++ b/src/canvas-base.c
@@ -0,0 +1,3820 @@
+/* This file is part of Ganv.
+ * Copyright 2007-2011 David Robillard <http://drobilla.net>
+ *
+ * Ganv is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or any later version.
+ *
+ * Ganv is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with Ganv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* Based on GnomeCanvas, by Federico Mena <federico@nuclecu.unam.mx>
+ * and Raph Levien <raph@gimp.org>
+ * Copyright 1997-2000 Free Software Foundation
+ */
+
+#include <math.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <gdk/gdkprivate.h>
+#include <gtk/gtk.h>
+#include <cairo.h>
+
+#include "libart_lgpl/art_rect.h"
+#include "libart_lgpl/art_rect_uta.h"
+#include "libart_lgpl/art_uta_rect.h"
+#include "libart_lgpl/art_uta_ops.h"
+
+#include "ganv/canvas-base.h"
+
+#include "./gettext.h"
+#include "./ganv-marshal.h"
+
+/* We must run our idle update handler *before* GDK wants to redraw. */
+#define CANVAS_IDLE_PRIORITY (GDK_PRIORITY_REDRAW - 5)
+
+static void ganv_canvas_base_request_update(GanvCanvasBase* canvas);
+static void group_add(GanvGroup* group,
+                      GanvItem*  item);
+static void group_remove(GanvGroup* group,
+                         GanvItem*  item);
+static void add_idle(GanvCanvasBase* canvas);
+
+
+/*** GanvItem ***/
+
+/* Some convenience stuff */
+#define GCI_UPDATE_MASK (GANV_CANVAS_BASE_UPDATE_REQUESTED | GANV_CANVAS_BASE_UPDATE_AFFINE \
+                         | GANV_CANVAS_BASE_UPDATE_CLIP | GANV_CANVAS_BASE_UPDATE_VISIBILITY)
+#define GCI_EPSILON 1e-18
+#define GCI_PRINT_MATRIX(s, a) g_print("%s %g %g %g %g %g %g\n", s, (a)[0], (a)[1], (a)[2], (a)[3], \
+                                       (a)[4], (a)[5])
+
+enum {
+	ITEM_PROP_0,
+	ITEM_PROP_PARENT
+};
+
+enum {
+	ITEM_EVENT,
+	ITEM_LAST_SIGNAL
+};
+
+static void ganv_item_class_init(GanvItemClass* class);
+static void ganv_item_init(GanvItem* item);
+static int  emit_event(GanvCanvasBase* canvas, GdkEvent* event);
+
+static guint item_signals[ITEM_LAST_SIGNAL];
+
+G_DEFINE_TYPE(GanvItem, ganv_item, GTK_TYPE_OBJECT)
+
+static GtkObjectClass * item_parent_class;
+
+/* Object initialization function for GanvItem */
+static void
+ganv_item_init(GanvItem* item)
+{
+	item->object.flags |= GANV_ITEM_VISIBLE;
+}
+
+/**
+ * ganv_item_new:
+ * @parent: The parent group for the new item.
+ * @type: The object type of the item.
+ * @first_arg_name: A list of object argument name/value pairs, NULL-terminated,
+ * used to configure the item.  For example, "fill_color", "black",
+ * "width_units", 5.0, NULL.
+ * @Varargs:
+ *
+ * Creates a new canvas item with @parent as its parent group.  The item is
+ * created at the top of its parent's stack, and starts up as visible.  The item
+ * is of the specified @type, for example, it can be
+ * ganv_canvas_base_rect_get_type().  The list of object arguments/value pairs is
+ * used to configure the item. If you need to pass construct time parameters, you
+ * should use g_object_new() to pass the parameters and
+ * ganv_item_construct() to set up the canvas item.
+ *
+ * Return value: The newly-created item.
+ **/
+GanvItem*
+ganv_item_new(GanvGroup* parent, GType type, const gchar* first_arg_name, ...)
+{
+	GanvItem* item;
+	va_list   args;
+
+	g_return_val_if_fail(GANV_IS_GROUP(parent), NULL);
+	g_return_val_if_fail(g_type_is_a(type, ganv_item_get_type()), NULL);
+
+	item = GANV_ITEM(g_object_new(type, NULL));
+
+	va_start(args, first_arg_name);
+	ganv_item_construct(item, parent, first_arg_name, args);
+	va_end(args);
+
+	return item;
+}
+
+/* Performs post-creation operations on a canvas item (adding it to its parent
+ * group, etc.)
+ */
+static void
+item_post_create_setup(GanvItem* item)
+{
+	group_add(GANV_GROUP(item->parent), item);
+
+	ganv_canvas_base_request_redraw(item->canvas, item->x1, item->y1, item->x2 + 1, item->y2 + 1);
+	item->canvas->need_repick = TRUE;
+}
+
+/* Set_property handler for canvas items */
+static void
+ganv_item_set_property(GObject* gobject, guint param_id,
+                       const GValue* value, GParamSpec* pspec)
+{
+	GanvItem* item;
+
+	g_return_if_fail(GANV_IS_ITEM(gobject));
+
+	item = GANV_ITEM(gobject);
+
+	switch (param_id) {
+	case ITEM_PROP_PARENT:
+		if (item->parent != NULL) {
+			g_warning("Cannot set `parent' argument after item has "
+			          "already been constructed.");
+		} else if (g_value_get_object(value)) {
+			item->parent = GANV_ITEM(g_value_get_object(value));
+			item->canvas = item->parent->canvas;
+			item_post_create_setup(item);
+		}
+		break;
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(gobject, param_id, pspec);
+		break;
+	}
+}
+
+/* Get_property handler for canvas items */
+static void
+ganv_item_get_property(GObject* gobject, guint param_id,
+                       GValue* value, GParamSpec* pspec)
+{
+	GanvItem* item;
+
+	g_return_if_fail(GANV_IS_ITEM(gobject));
+
+	item = GANV_ITEM(gobject);
+
+	switch (param_id) {
+	case ITEM_PROP_PARENT:
+		g_value_set_object(value, item->parent);
+		break;
+
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(gobject, param_id, pspec);
+		break;
+	}
+}
+
+/**
+ * ganv_item_construct:
+ * @item: An unconstructed canvas item.
+ * @parent: The parent group for the item.
+ * @first_arg_name: The name of the first argument for configuring the item.
+ * @args: The list of arguments used to configure the item.
+ *
+ * Constructs a canvas item; meant for use only by item implementations.
+ **/
+void
+ganv_item_construct(GanvItem* item, GanvGroup* parent,
+                    const gchar* first_arg_name, va_list args)
+{
+	g_return_if_fail(GANV_IS_GROUP(parent));
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	item->parent = GANV_ITEM(parent);
+	item->canvas = item->parent->canvas;
+
+	g_object_set_valist(G_OBJECT(item), first_arg_name, args);
+
+	item_post_create_setup(item);
+}
+
+/* If the item is visible, requests a redraw of it. */
+static void
+redraw_if_visible(GanvItem* item)
+{
+	if (item->object.flags & GANV_ITEM_VISIBLE) {
+		ganv_canvas_base_request_redraw(item->canvas, item->x1, item->y1, item->x2 + 1,
+		                                item->y2 + 1);
+	}
+}
+
+/* Standard object dispose function for canvas items */
+static void
+ganv_item_dispose(GObject* object)
+{
+	GanvItem* item;
+
+	g_return_if_fail(GANV_IS_ITEM(object));
+
+	item = GANV_ITEM(object);
+
+	if (item->canvas) {
+		redraw_if_visible(item);
+	}
+
+	/* Make the canvas forget about us */
+
+	if (item->canvas && ( item == item->canvas->current_item) ) {
+		item->canvas->current_item = NULL;
+		item->canvas->need_repick  = TRUE;
+	}
+
+	if (item->canvas && ( item == item->canvas->new_current_item) ) {
+		item->canvas->new_current_item = NULL;
+		item->canvas->need_repick      = TRUE;
+	}
+
+	if (item->canvas && ( item == item->canvas->grabbed_item) ) {
+		item->canvas->grabbed_item = NULL;
+		gdk_pointer_ungrab(GDK_CURRENT_TIME);
+	}
+
+	if (item->canvas && ( item == item->canvas->focused_item) ) {
+		item->canvas->focused_item = NULL;
+	}
+
+	/* Normal destroy stuff */
+
+	if (item->object.flags & GANV_ITEM_MAPPED) {
+		(*GANV_ITEM_GET_CLASS(item)->unmap)(item);
+	}
+
+	if (item->object.flags & GANV_ITEM_REALIZED) {
+		(*GANV_ITEM_GET_CLASS(item)->unrealize)(item);
+	}
+
+	if (item->parent) {
+		group_remove(GANV_GROUP(item->parent), item);
+	}
+
+	g_free(item->xform);
+	item->xform = NULL;
+
+	G_OBJECT_CLASS(item_parent_class)->dispose(object);
+	/* items should remove any reference to item->canvas after the
+	   first ::destroy */
+	item->canvas = NULL;
+}
+
+/* Realize handler for canvas items */
+static void
+ganv_item_realize(GanvItem* item)
+{
+	GTK_OBJECT_SET_FLAGS(item, GANV_ITEM_REALIZED);
+
+	ganv_item_request_update(item);
+}
+
+/* Unrealize handler for canvas items */
+static void
+ganv_item_unrealize(GanvItem* item)
+{
+	GTK_OBJECT_UNSET_FLAGS(item, GANV_ITEM_REALIZED);
+}
+
+/* Map handler for canvas items */
+static void
+ganv_item_map(GanvItem* item)
+{
+	GTK_OBJECT_SET_FLAGS(item, GANV_ITEM_MAPPED);
+}
+
+/* Unmap handler for canvas items */
+static void
+ganv_item_unmap(GanvItem* item)
+{
+	GTK_OBJECT_UNSET_FLAGS(item, GANV_ITEM_MAPPED);
+}
+
+/* Update handler for canvas items */
+static void
+ganv_item_update(GanvItem* item, double* affine, ArtSVP* clip_path, int flags)
+{
+	GTK_OBJECT_UNSET_FLAGS(item, GANV_ITEM_NEED_UPDATE);
+	GTK_OBJECT_UNSET_FLAGS(item, GANV_ITEM_NEED_AFFINE);
+	GTK_OBJECT_UNSET_FLAGS(item, GANV_ITEM_NEED_CLIP);
+	GTK_OBJECT_UNSET_FLAGS(item, GANV_ITEM_NEED_VIS);
+}
+
+#define noHACKISH_AFFINE
+
+/*
+ * This routine invokes the update method of the item
+ * Please notice, that we take parent to canvas pixel matrix as argument
+ * unlike virtual method ::update, whose argument is item 2 canvas pixel
+ * matrix
+ *
+ * I will try to force somewhat meaningful naming for affines (Lauris)
+ * General naming rule is FROM2TO, where FROM and TO are abbreviations
+ * So p2cpx is Parent2CanvasPixel and i2cpx is Item2CanvasPixel
+ * I hope that this helps to keep track of what really happens
+ *
+ */
+
+static void
+ganv_item_invoke_update(GanvItem* item, double* p2cpx, ArtSVP* clip_path, int flags)
+{
+	int     child_flags;
+	gdouble i2cpx[6];
+
+#ifdef HACKISH_AFFINE
+	double i2w[6], w2c[6], i2c[6];
+#endif
+
+	child_flags = flags;
+	if (!(item->object.flags & GANV_ITEM_VISIBLE)) {
+		child_flags &= ~GANV_CANVAS_BASE_UPDATE_IS_VISIBLE;
+	}
+
+	/* Calculate actual item transformation matrix */
+
+	if (item->xform) {
+		if (item->object.flags & GANV_ITEM_AFFINE_FULL) {
+			/* Item has full affine */
+			art_affine_multiply(i2cpx, item->xform, p2cpx);
+		} else {
+			/* Item has only translation */
+			memcpy(i2cpx, p2cpx, 4 * sizeof(gdouble));
+			i2cpx[4] = item->xform[0] * p2cpx[0] + item->xform[1] * p2cpx[2] + p2cpx[4];
+			i2cpx[5] = item->xform[0] * p2cpx[1] + item->xform[1] * p2cpx[3] + p2cpx[5];
+		}
+	} else {
+		/* Item has no matrix (i.e. identity) */
+		memcpy(i2cpx, p2cpx, 6 * sizeof(gdouble));
+	}
+
+#ifdef HACKISH_AFFINE
+	ganv_item_i2w_affine(item, i2w);
+	ganv_canvas_base_w2c_affine(item->canvas, w2c);
+	art_affine_multiply(i2c, i2w, w2c);
+	/* invariant (doesn't hold now): child_affine == i2c */
+	child_affine = i2c;
+#endif
+
+	/* apply object flags to child flags */
+
+	child_flags &= ~GANV_CANVAS_BASE_UPDATE_REQUESTED;
+
+	if (item->object.flags & GANV_ITEM_NEED_UPDATE) {
+		child_flags |= GANV_CANVAS_BASE_UPDATE_REQUESTED;
+	}
+
+	if (item->object.flags & GANV_ITEM_NEED_AFFINE) {
+		child_flags |= GANV_CANVAS_BASE_UPDATE_AFFINE;
+	}
+
+	if (item->object.flags & GANV_ITEM_NEED_CLIP) {
+		child_flags |= GANV_CANVAS_BASE_UPDATE_CLIP;
+	}
+
+	if (item->object.flags & GANV_ITEM_NEED_VIS) {
+		child_flags |= GANV_CANVAS_BASE_UPDATE_VISIBILITY;
+	}
+
+	if (child_flags & GCI_UPDATE_MASK) {
+		if (GANV_ITEM_GET_CLASS(item)->update) {
+			GANV_ITEM_GET_CLASS(item)->update(item, i2cpx, clip_path, child_flags);
+		}
+	}
+}
+
+/*
+ * This routine invokes the point method of the item.
+ * The arguments x, y should be in the parent item local coordinates.
+ *
+ * This is potentially evil, as we are relying on matrix inversion (Lauris)
+ */
+
+static double
+ganv_item_invoke_point(GanvItem* item, double x, double y, int cx, int cy,
+                       GanvItem** actual_item)
+{
+	/* Calculate x & y in item local coordinates */
+
+	if (item->xform) {
+		if (item->object.flags & GANV_ITEM_AFFINE_FULL) {
+			gdouble p2i[6], t;
+			/* Item has full affine */
+			art_affine_invert(p2i, item->xform);
+			t = x * p2i[0] + y * p2i[2] + p2i[4];
+			y = x * p2i[1] + y * p2i[3] + p2i[5];
+			x = t;
+		} else {
+			/* Item has only translation */
+			x -= item->xform[0];
+			y -= item->xform[1];
+		}
+	}
+
+#ifdef HACKISH_AFFINE
+	double   i2w[6], w2c[6], i2c[6], c2i[6];
+	ArtPoint c, i;
+#endif
+
+#ifdef HACKISH_AFFINE
+	ganv_item_i2w_affine(item, i2w);
+	ganv_canvas_base_w2c_affine(item->canvas, w2c);
+	art_affine_multiply(i2c, i2w, w2c);
+	art_affine_invert(c2i, i2c);
+	c.x = cx;
+	c.y = cy;
+	art_affine_point(&i, &c, c2i);
+	x = i.x;
+	y = i.y;
+#endif
+
+	if (GANV_ITEM_GET_CLASS(item)->point) {
+		return GANV_ITEM_GET_CLASS(item)->point(item, x, y, cx, cy, actual_item);
+	}
+
+	return 1e18;
+}
+
+/**
+ * ganv_item_set:
+ * @item: A canvas item.
+ * @first_arg_name: The list of object argument name/value pairs used to configure the item.
+ * @Varargs:
+ *
+ * Configures a canvas item.  The arguments in the item are set to the specified
+ * values, and the item is repainted as appropriate.
+ **/
+void
+ganv_item_set(GanvItem* item, const gchar* first_arg_name, ...)
+{
+	va_list args;
+
+	va_start(args, first_arg_name);
+	ganv_item_set_valist(item, first_arg_name, args);
+	va_end(args);
+}
+
+/**
+ * ganv_item_set_valist:
+ * @item: A canvas item.
+ * @first_arg_name: The name of the first argument used to configure the item.
+ * @args: The list of object argument name/value pairs used to configure the item.
+ *
+ * Configures a canvas item.  The arguments in the item are set to the specified
+ * values, and the item is repainted as appropriate.
+ **/
+void
+ganv_item_set_valist(GanvItem* item, const gchar* first_arg_name, va_list args)
+{
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	g_object_set_valist(G_OBJECT(item), first_arg_name, args);
+
+	item->canvas->need_repick = TRUE;
+}
+
+/**
+ * ganv_item_affine_relative:
+ * @item: A canvas item.
+ * @affine: An affine transformation matrix.
+ *
+ * Combines the specified affine transformation matrix with the item's current
+ * transformation. NULL affine is not allowed.
+ **/
+#define GCIAR_EPSILON 1e-6
+void
+ganv_item_affine_relative(GanvItem* item, const double affine[6])
+{
+	gdouble i2p[6];
+
+	g_return_if_fail(item != NULL);
+	g_return_if_fail(GANV_IS_ITEM(item));
+	g_return_if_fail(affine != NULL);
+
+	/* Calculate actual item transformation matrix */
+
+	if (item->xform) {
+		if (item->object.flags & GANV_ITEM_AFFINE_FULL) {
+			/* Item has full affine */
+			art_affine_multiply(i2p, affine, item->xform);
+		} else {
+			/* Item has only translation */
+			memcpy(i2p, affine, 6 * sizeof(gdouble));
+			i2p[4] += item->xform[0];
+			i2p[5] += item->xform[1];
+		}
+	} else {
+		/* Item has no matrix (i.e. identity) */
+		memcpy(i2p, affine, 6 * sizeof(gdouble));
+	}
+
+	ganv_item_affine_absolute(item, i2p);
+}
+
+/**
+ * ganv_item_affine_absolute:
+ * @item: A canvas item.
+ * @affine: An affine transformation matrix.
+ *
+ * Makes the item's affine transformation matrix be equal to the specified
+ * matrix. NULL affine is treated as identity.
+ **/
+void
+ganv_item_affine_absolute(GanvItem* item, const double i2p[6])
+{
+	g_return_if_fail(item != NULL);
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	if (i2p
+	    && (fabs(i2p[0] - 1.0) < GCI_EPSILON)
+	    && (fabs(i2p[1] - 0.0) < GCI_EPSILON)
+	    && (fabs(i2p[2] - 0.0) < GCI_EPSILON)
+	    && (fabs(i2p[3] - 1.0) < GCI_EPSILON)
+	    && (fabs(i2p[4] - 0.0) < GCI_EPSILON)
+	    && (fabs(i2p[5] - 0.0) < GCI_EPSILON)) {
+		/* We are identity */
+		i2p = NULL;
+	}
+
+	if (i2p) {
+		if (item->xform && !(item->object.flags & GANV_ITEM_AFFINE_FULL)) {
+			/* We do not want to deal with translation-only affines */
+			g_free(item->xform);
+			item->xform = NULL;
+		}
+		if (!item->xform) {
+			item->xform = g_new(gdouble, 6);
+		}
+		memcpy(item->xform, i2p, 6 * sizeof(gdouble));
+		item->object.flags |= GANV_ITEM_AFFINE_FULL;
+	} else {
+		if (item->xform) {
+			g_free(item->xform);
+			item->xform = NULL;
+		}
+	}
+
+	if (!(item->object.flags & GANV_ITEM_NEED_AFFINE)) {
+		/* Request update */
+		item->object.flags |= GANV_ITEM_NEED_AFFINE;
+		ganv_item_request_update(item);
+	}
+
+	item->canvas->need_repick = TRUE;
+}
+
+/**
+ * ganv_item_move:
+ * @item: A canvas item.
+ * @dx: Horizontal offset.
+ * @dy: Vertical offset.
+ *
+ * Moves a canvas item by creating an affine transformation matrix for
+ * translation by using the specified values. This happens in item
+ * local coordinate system, so if you have nontrivial transform, it
+ * most probably does not do, what you want.
+ **/
+void
+ganv_item_move(GanvItem* item, double dx, double dy)
+{
+	double translate[6];
+
+	g_return_if_fail(item != NULL);
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	art_affine_translate(translate, dx, dy);
+
+	ganv_item_affine_relative(item, translate);
+}
+
+/* Convenience function to reorder items in a group's child list.  This puts the
+ * specified link after the "before" link. Returns TRUE if the list was changed.
+ */
+static gboolean
+put_item_after(GList* link, GList* before)
+{
+	GanvGroup* parent;
+	GList*     old_before, * old_after;
+	GList*     after;
+
+	parent = GANV_GROUP(GANV_ITEM(link->data)->parent);
+
+	if (before) {
+		after = before->next;
+	} else {
+		after = parent->item_list;
+	}
+
+	if (( before == link) || ( after == link) ) {
+		return FALSE;
+	}
+
+	/* Unlink */
+
+	old_before = link->prev;
+	old_after  = link->next;
+
+	if (old_before) {
+		old_before->next = old_after;
+	} else {
+		parent->item_list = old_after;
+	}
+
+	if (old_after) {
+		old_after->prev = old_before;
+	} else {
+		parent->item_list_end = old_before;
+	}
+
+	/* Relink */
+
+	link->prev = before;
+	if (before) {
+		before->next = link;
+	} else {
+		parent->item_list = link;
+	}
+
+	link->next = after;
+	if (after) {
+		after->prev = link;
+	} else {
+		parent->item_list_end = link;
+	}
+
+	return TRUE;
+}
+
+/**
+ * ganv_item_raise:
+ * @item: A canvas item.
+ * @positions: Number of steps to raise the item.
+ *
+ * Raises the item in its parent's stack by the specified number of positions.
+ * If the number of positions is greater than the distance to the top of the
+ * stack, then the item is put at the top.
+ **/
+void
+ganv_item_raise(GanvItem* item, int positions)
+{
+	GList*     link, * before;
+	GanvGroup* parent;
+
+	g_return_if_fail(GANV_IS_ITEM(item));
+	g_return_if_fail(positions >= 0);
+
+	if (!item->parent || ( positions == 0) ) {
+		return;
+	}
+
+	parent = GANV_GROUP(item->parent);
+	link   = g_list_find(parent->item_list, item);
+	g_assert(link != NULL);
+
+	for (before = link; positions && before; positions--) {
+		before = before->next;
+	}
+
+	if (!before) {
+		before = parent->item_list_end;
+	}
+
+	if (put_item_after(link, before)) {
+		redraw_if_visible(item);
+		item->canvas->need_repick = TRUE;
+	}
+}
+
+/**
+ * ganv_item_lower:
+ * @item: A canvas item.
+ * @positions: Number of steps to lower the item.
+ *
+ * Lowers the item in its parent's stack by the specified number of positions.
+ * If the number of positions is greater than the distance to the bottom of the
+ * stack, then the item is put at the bottom.
+ **/
+void
+ganv_item_lower(GanvItem* item, int positions)
+{
+	GList*     link, * before;
+	GanvGroup* parent;
+
+	g_return_if_fail(GANV_IS_ITEM(item));
+	g_return_if_fail(positions >= 1);
+
+	if (!item->parent || ( positions == 0) ) {
+		return;
+	}
+
+	parent = GANV_GROUP(item->parent);
+	link   = g_list_find(parent->item_list, item);
+	g_assert(link != NULL);
+
+	if (link->prev) {
+		for (before = link->prev; positions && before; positions--) {
+			before = before->prev;
+		}
+	} else {
+		before = NULL;
+	}
+
+	if (put_item_after(link, before)) {
+		redraw_if_visible(item);
+		item->canvas->need_repick = TRUE;
+	}
+}
+
+/**
+ * ganv_item_raise_to_top:
+ * @item: A canvas item.
+ *
+ * Raises an item to the top of its parent's stack.
+ **/
+void
+ganv_item_raise_to_top(GanvItem* item)
+{
+	GList*     link;
+	GanvGroup* parent;
+
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	if (!item->parent) {
+		return;
+	}
+
+	parent = GANV_GROUP(item->parent);
+	link   = g_list_find(parent->item_list, item);
+	g_assert(link != NULL);
+
+	if (put_item_after(link, parent->item_list_end)) {
+		redraw_if_visible(item);
+		item->canvas->need_repick = TRUE;
+	}
+}
+
+/**
+ * ganv_item_lower_to_bottom:
+ * @item: A canvas item.
+ *
+ * Lowers an item to the bottom of its parent's stack.
+ **/
+void
+ganv_item_lower_to_bottom(GanvItem* item)
+{
+	GList*     link;
+	GanvGroup* parent;
+
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	if (!item->parent) {
+		return;
+	}
+
+	parent = GANV_GROUP(item->parent);
+	link   = g_list_find(parent->item_list, item);
+	g_assert(link != NULL);
+
+	if (put_item_after(link, NULL)) {
+		redraw_if_visible(item);
+		item->canvas->need_repick = TRUE;
+	}
+}
+
+/**
+ * ganv_item_show:
+ * @item: A canvas item.
+ *
+ * Shows a canvas item.  If the item was already shown, then no action is taken.
+ **/
+void
+ganv_item_show(GanvItem* item)
+{
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	if (!(item->object.flags & GANV_ITEM_VISIBLE)) {
+		item->object.flags |= GANV_ITEM_VISIBLE;
+		ganv_canvas_base_request_redraw(item->canvas, item->x1, item->y1, item->x2 + 1,
+		                                item->y2 + 1);
+		item->canvas->need_repick = TRUE;
+	}
+}
+
+/**
+ * ganv_item_hide:
+ * @item: A canvas item.
+ *
+ * Hides a canvas item.  If the item was already hidden, then no action is
+ * taken.
+ **/
+void
+ganv_item_hide(GanvItem* item)
+{
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	if (item->object.flags & GANV_ITEM_VISIBLE) {
+		item->object.flags &= ~GANV_ITEM_VISIBLE;
+		ganv_canvas_base_request_redraw(item->canvas, item->x1, item->y1, item->x2 + 1,
+		                                item->y2 + 1);
+		item->canvas->need_repick = TRUE;
+	}
+}
+
+/**
+ * ganv_item_grab:
+ * @item: A canvas item.
+ * @event_mask: Mask of events that will be sent to this item.
+ * @cursor: If non-NULL, the cursor that will be used while the grab is active.
+ * @etime: The timestamp required for grabbing the mouse, or GDK_CURRENT_TIME.
+ *
+ * Specifies that all events that match the specified event mask should be sent
+ * to the specified item, and also grabs the mouse by calling
+ * gdk_pointer_grab().  The event mask is also used when grabbing the pointer.
+ * If @cursor is not NULL, then that cursor is used while the grab is active.
+ * The @etime parameter is the timestamp required for grabbing the mouse.
+ *
+ * Return value: If an item was already grabbed, it returns %GDK_GRAB_ALREADY_GRABBED.  If
+ * the specified item was hidden by calling ganv_item_hide(), then it
+ * returns %GDK_GRAB_NOT_VIEWABLE.  Else, it returns the result of calling
+ * gdk_pointer_grab().
+ **/
+int
+ganv_item_grab(GanvItem* item, guint event_mask, GdkCursor* cursor, guint32 etime)
+{
+	int retval;
+
+	g_return_val_if_fail(GANV_IS_ITEM(item), GDK_GRAB_NOT_VIEWABLE);
+	g_return_val_if_fail(GTK_WIDGET_MAPPED(item->canvas), GDK_GRAB_NOT_VIEWABLE);
+
+	if (item->canvas->grabbed_item) {
+		return GDK_GRAB_ALREADY_GRABBED;
+	}
+
+	if (!(item->object.flags & GANV_ITEM_VISIBLE)) {
+		return GDK_GRAB_NOT_VIEWABLE;
+	}
+
+	retval = gdk_pointer_grab(item->canvas->layout.bin_window,
+	                          FALSE,
+	                          event_mask,
+	                          NULL,
+	                          cursor,
+	                          etime);
+
+	if (retval != GDK_GRAB_SUCCESS) {
+		return retval;
+	}
+
+	item->canvas->grabbed_item       = item;
+	item->canvas->grabbed_event_mask = event_mask;
+	item->canvas->current_item       = item; /* So that events go to the grabbed item */
+
+	return retval;
+}
+
+/**
+ * ganv_item_ungrab:
+ * @item: A canvas item that holds a grab.
+ * @etime: The timestamp for ungrabbing the mouse.
+ *
+ * Ungrabs the item, which must have been grabbed in the canvas, and ungrabs the
+ * mouse.
+ **/
+void
+ganv_item_ungrab(GanvItem* item, guint32 etime)
+{
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	if (item->canvas->grabbed_item != item) {
+		return;
+	}
+
+	item->canvas->grabbed_item = NULL;
+
+	gdk_pointer_ungrab(etime);
+}
+
+/**
+ * ganv_item_i2w_affine:
+ * @item: A canvas item
+ * @affine: An affine transformation matrix (return value).
+ *
+ * Gets the affine transform that converts from the item's coordinate system to
+ * world coordinates.
+ **/
+void
+ganv_item_i2w_affine(GanvItem* item, double affine[6])
+{
+	g_return_if_fail(GANV_IS_ITEM(item));
+	g_return_if_fail(affine != NULL);
+
+	art_affine_identity(affine);
+
+	while (item) {
+		if (item->xform != NULL) {
+			if (item->object.flags & GANV_ITEM_AFFINE_FULL) {
+				art_affine_multiply(affine, affine, item->xform);
+			} else {
+				affine[4] += item->xform[0];
+				affine[5] += item->xform[1];
+			}
+		}
+
+		item = item->parent;
+	}
+}
+
+/**
+ * ganv_item_w2i:
+ * @item: A canvas item.
+ * @x: X coordinate to convert (input/output value).
+ * @y: Y coordinate to convert (input/output value).
+ *
+ * Converts a coordinate pair from world coordinates to item-relative
+ * coordinates.
+ **/
+void
+ganv_item_w2i(GanvItem* item, double* x, double* y)
+{
+	double   affine[6], inv[6];
+	ArtPoint w, i;
+
+	g_return_if_fail(GANV_IS_ITEM(item));
+	g_return_if_fail(x != NULL);
+	g_return_if_fail(y != NULL);
+
+	ganv_item_i2w_affine(item, affine);
+	art_affine_invert(inv, affine);
+	w.x = *x;
+	w.y = *y;
+	art_affine_point(&i, &w, inv);
+	*x = i.x;
+	*y = i.y;
+}
+
+/**
+ * ganv_item_i2w:
+ * @item: A canvas item.
+ * @x: X coordinate to convert (input/output value).
+ * @y: Y coordinate to convert (input/output value).
+ *
+ * Converts a coordinate pair from item-relative coordinates to world
+ * coordinates.
+ **/
+void
+ganv_item_i2w(GanvItem* item, double* x, double* y)
+{
+	double   affine[6];
+	ArtPoint w, i;
+
+	g_return_if_fail(GANV_IS_ITEM(item));
+	g_return_if_fail(x != NULL);
+	g_return_if_fail(y != NULL);
+
+	ganv_item_i2w_affine(item, affine);
+	i.x = *x;
+	i.y = *y;
+	art_affine_point(&w, &i, affine);
+	*x = w.x;
+	*y = w.y;
+}
+
+/**
+ * ganv_item_i2c_affine:
+ * @item: A canvas item.
+ * @affine: An affine transformation matrix (return value).
+ *
+ * Gets the affine transform that converts from item-relative coordinates to
+ * canvas pixel coordinates.
+ **/
+void
+ganv_item_i2c_affine(GanvItem* item, double affine[6])
+{
+	double i2w[6], w2c[6];
+
+	ganv_item_i2w_affine(item, i2w);
+	ganv_canvas_base_w2c_affine(item->canvas, w2c);
+	art_affine_multiply(affine, i2w, w2c);
+}
+
+/* Returns whether the item is an inferior of or is equal to the parent. */
+static int
+is_descendant(GanvItem* item, GanvItem* parent)
+{
+	for (; item; item = item->parent) {
+		if (item == parent) {
+			return TRUE;
+		}
+	}
+
+	return FALSE;
+}
+
+/**
+ * ganv_item_reparent:
+ * @item: A canvas item.
+ * @new_group: A canvas group.
+ *
+ * Changes the parent of the specified item to be the new group.  The item keeps
+ * its group-relative coordinates as for its old parent, so the item may change
+ * its absolute position within the canvas.
+ **/
+void
+ganv_item_reparent(GanvItem* item, GanvGroup* new_group)
+{
+	g_return_if_fail(GANV_IS_ITEM(item));
+	g_return_if_fail(GANV_IS_GROUP(new_group));
+
+	/* Both items need to be in the same canvas */
+	g_return_if_fail(item->canvas == GANV_ITEM(new_group)->canvas);
+
+	/* The group cannot be an inferior of the item or be the item itself --
+	 * this also takes care of the case where the item is the root item of
+	 * the canvas.  */
+	g_return_if_fail(!is_descendant(GANV_ITEM(new_group), item));
+
+	/* Everything is ok, now actually reparent the item */
+
+	g_object_ref(G_OBJECT(item)); /* protect it from the unref in group_remove */
+
+	redraw_if_visible(item);
+
+	group_remove(GANV_GROUP(item->parent), item);
+	item->parent = GANV_ITEM(new_group);
+	group_add(new_group, item);
+
+	/* Redraw and repick */
+
+	redraw_if_visible(item);
+	item->canvas->need_repick = TRUE;
+
+	g_object_unref(G_OBJECT(item));
+}
+
+/**
+ * ganv_item_grab_focus:
+ * @item: A canvas item.
+ *
+ * Makes the specified item take the keyboard focus, so all keyboard events will
+ * be sent to it.  If the canvas widget itself did not have the focus, it grabs
+ * it as well.
+ **/
+void
+ganv_item_grab_focus(GanvItem* item)
+{
+	GanvItem* focused_item;
+	GdkEvent  ev;
+
+	g_return_if_fail(GANV_IS_ITEM(item));
+	g_return_if_fail(GTK_WIDGET_CAN_FOCUS(GTK_WIDGET(item->canvas)));
+
+	focused_item = item->canvas->focused_item;
+
+	if (focused_item) {
+		ev.focus_change.type       = GDK_FOCUS_CHANGE;
+		ev.focus_change.window     = GTK_LAYOUT(item->canvas)->bin_window;
+		ev.focus_change.send_event = FALSE;
+		ev.focus_change.in         = FALSE;
+
+		emit_event(item->canvas, &ev);
+	}
+
+	item->canvas->focused_item = item;
+	gtk_widget_grab_focus(GTK_WIDGET(item->canvas));
+
+	if (focused_item) {
+		ev.focus_change.type       = GDK_FOCUS_CHANGE;
+		ev.focus_change.window     = GTK_LAYOUT(item->canvas)->bin_window;
+		ev.focus_change.send_event = FALSE;
+		ev.focus_change.in         = TRUE;
+
+		emit_event(item->canvas, &ev);
+	}
+}
+
+/**
+ * ganv_item_get_bounds:
+ * @item: A canvas item.
+ * @x1: Leftmost edge of the bounding box (return value).
+ * @y1: Upper edge of the bounding box (return value).
+ * @x2: Rightmost edge of the bounding box (return value).
+ * @y2: Lower edge of the bounding box (return value).
+ *
+ * Queries the bounding box of a canvas item.  The bounds are returned in the
+ * coordinate system of the item's parent.
+ **/
+void
+ganv_item_get_bounds(GanvItem* item, double* x1, double* y1, double* x2, double* y2)
+{
+	double   tx1, ty1, tx2, ty2;
+	ArtPoint p1, p2, p3, p4;
+	ArtPoint q1, q2, q3, q4;
+	double   min_x1, min_y1, min_x2, min_y2;
+	double   max_x1, max_y1, max_x2, max_y2;
+
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	tx1 = ty1 = tx2 = ty2 = 0.0;
+
+	/* Get the item's bounds in its coordinate system */
+
+	if (GANV_ITEM_GET_CLASS(item)->bounds) {
+		(*GANV_ITEM_GET_CLASS(item)->bounds)(item, &tx1, &ty1, &tx2, &ty2);
+	}
+
+	/* Make the bounds relative to the item's parent coordinate system */
+
+	if (item->xform && (item->object.flags & GANV_ITEM_AFFINE_FULL)) {
+		p1.x = p2.x = tx1;
+		p1.y = p4.y = ty1;
+		p3.x = p4.x = tx2;
+		p2.y = p3.y = ty2;
+
+		art_affine_point(&q1, &p1, item->xform);
+		art_affine_point(&q2, &p2, item->xform);
+		art_affine_point(&q3, &p3, item->xform);
+		art_affine_point(&q4, &p4, item->xform);
+
+		if (q1.x < q2.x) {
+			min_x1 = q1.x;
+			max_x1 = q2.x;
+		} else {
+			min_x1 = q2.x;
+			max_x1 = q1.x;
+		}
+
+		if (q1.y < q2.y) {
+			min_y1 = q1.y;
+			max_y1 = q2.y;
+		} else {
+			min_y1 = q2.y;
+			max_y1 = q1.y;
+		}
+
+		if (q3.x < q4.x) {
+			min_x2 = q3.x;
+			max_x2 = q4.x;
+		} else {
+			min_x2 = q4.x;
+			max_x2 = q3.x;
+		}
+
+		if (q3.y < q4.y) {
+			min_y2 = q3.y;
+			max_y2 = q4.y;
+		} else {
+			min_y2 = q4.y;
+			max_y2 = q3.y;
+		}
+
+		tx1 = MIN(min_x1, min_x2);
+		ty1 = MIN(min_y1, min_y2);
+		tx2 = MAX(max_x1, max_x2);
+		ty2 = MAX(max_y1, max_y2);
+	} else if (item->xform) {
+		tx1 += item->xform[0];
+		ty1 += item->xform[1];
+		tx2 += item->xform[0];
+		ty2 += item->xform[1];
+	}
+
+	/* Return the values */
+
+	if (x1) {
+		*x1 = tx1;
+	}
+
+	if (y1) {
+		*y1 = ty1;
+	}
+
+	if (x2) {
+		*x2 = tx2;
+	}
+
+	if (y2) {
+		*y2 = ty2;
+	}
+}
+
+/**
+ * ganv_item_request_update
+ * @item: A canvas item.
+ *
+ * To be used only by item implementations.  Requests that the canvas queue an
+ * update for the specified item.
+ **/
+void
+ganv_item_request_update(GanvItem* item)
+{
+	if (item->object.flags & GANV_ITEM_NEED_UPDATE) {
+		return;
+	}
+
+	item->object.flags |= GANV_ITEM_NEED_UPDATE;
+
+	if (item->parent != NULL) {
+		/* Recurse up the tree */
+		ganv_item_request_update(item->parent);
+	} else {
+		/* Have reached the top of the tree, make sure the update call gets scheduled. */
+		ganv_canvas_base_request_update(item->canvas);
+	}
+}
+
+/*** GanvGroup ***/
+
+
+enum {
+	GROUP_PROP_0,
+	GROUP_PROP_X,
+	GROUP_PROP_Y
+};
+
+
+static void ganv_group_class_init(GanvGroupClass* class);
+static void ganv_group_init(GanvGroup* group);
+static void ganv_group_set_property(GObject*      object,
+                                    guint         param_id,
+                                    const GValue* value,
+                                    GParamSpec*   pspec);
+static void ganv_group_get_property(GObject*    object,
+                                    guint       param_id,
+                                    GValue*     value,
+                                    GParamSpec* pspec);
+
+static void ganv_group_destroy(GtkObject* object);
+
+static void ganv_group_update(GanvItem* item, double* affine,
+                              ArtSVP* clip_path, int flags);
+static void ganv_group_realize(GanvItem* item);
+static void ganv_group_unrealize(GanvItem* item);
+static void ganv_group_map(GanvItem* item);
+static void ganv_group_unmap(GanvItem* item);
+static void ganv_group_draw(GanvItem* item, GdkDrawable* drawable,
+                            int x, int y, int width, int height);
+static double ganv_group_point(GanvItem* item, double x, double y,
+                               int cx, int cy,
+                               GanvItem** actual_item);
+static void ganv_group_bounds(GanvItem* item, double* x1, double* y1,
+                              double* x2, double* y2);
+
+
+static GanvItemClass* group_parent_class;
+
+G_DEFINE_TYPE(GanvGroup, ganv_group, GANV_TYPE_ITEM)
+
+/* Class initialization function for GanvGroupClass */
+static void
+ganv_group_class_init(GanvGroupClass* class)
+{
+	GObjectClass*   gobject_class;
+	GtkObjectClass* object_class;
+	GanvItemClass*  item_class;
+
+	gobject_class = (GObjectClass*)class;
+	object_class  = (GtkObjectClass*)class;
+	item_class    = (GanvItemClass*)class;
+
+	group_parent_class = g_type_class_peek_parent(class);
+
+	gobject_class->set_property = ganv_group_set_property;
+	gobject_class->get_property = ganv_group_get_property;
+
+	g_object_class_install_property
+	    (gobject_class, GROUP_PROP_X,
+	    g_param_spec_double("x",
+	                        _("X"),
+	                        _("X"),
+	                        -G_MAXDOUBLE, G_MAXDOUBLE, 0.0,
+	                        (G_PARAM_READABLE | G_PARAM_WRITABLE)));
+	g_object_class_install_property
+	    (gobject_class, GROUP_PROP_Y,
+	    g_param_spec_double("y",
+	                        _("Y"),
+	                        _("Y"),
+	                        -G_MAXDOUBLE, G_MAXDOUBLE, 0.0,
+	                        (G_PARAM_READABLE | G_PARAM_WRITABLE)));
+
+	object_class->destroy = ganv_group_destroy;
+
+	item_class->update    = ganv_group_update;
+	item_class->realize   = ganv_group_realize;
+	item_class->unrealize = ganv_group_unrealize;
+	item_class->map       = ganv_group_map;
+	item_class->unmap     = ganv_group_unmap;
+	item_class->draw      = ganv_group_draw;
+	item_class->point     = ganv_group_point;
+	item_class->bounds    = ganv_group_bounds;
+}
+
+/* Object initialization function for GanvGroup */
+static void
+ganv_group_init(GanvGroup* group)
+{
+#if 0
+	group->xpos = 0.0;
+	group->ypos = 0.0;
+#endif
+}
+
+/* Translate handler for canvas groups */
+static double*
+ganv_canvas_base_ensure_translate(GanvItem* item)
+{
+	if (item->xform == NULL) {
+		GTK_OBJECT_UNSET_FLAGS(item, GANV_ITEM_AFFINE_FULL);
+		item->xform    = g_new(double, 2);
+		item->xform[0] = 0.0;
+		item->xform[1] = 0.0;
+		return item->xform;
+	} else if (item->object.flags & GANV_ITEM_AFFINE_FULL) {
+		return item->xform + 4;
+	} else {
+		return item->xform;
+	}
+}
+
+/* Set_property handler for canvas groups */
+static void
+ganv_group_set_property(GObject* gobject, guint param_id,
+                        const GValue* value, GParamSpec* pspec)
+{
+	GanvItem* item;
+	double*   xlat;
+
+	g_return_if_fail(GANV_IS_GROUP(gobject));
+
+	item = GANV_ITEM(gobject);
+
+	switch (param_id) {
+	case GROUP_PROP_X:
+		xlat    = ganv_canvas_base_ensure_translate(item);
+		xlat[0] = g_value_get_double(value);
+		break;
+
+	case GROUP_PROP_Y:
+		xlat    = ganv_canvas_base_ensure_translate(item);
+		xlat[1] = g_value_get_double(value);
+		break;
+
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(gobject, param_id, pspec);
+		break;
+	}
+}
+
+/* Get_property handler for canvas groups */
+static void
+ganv_group_get_property(GObject* gobject, guint param_id,
+                        GValue* value, GParamSpec* pspec)
+{
+	GanvItem* item;
+
+	g_return_if_fail(GANV_IS_GROUP(gobject));
+
+	item = GANV_ITEM(gobject);
+
+	switch (param_id) {
+	case GROUP_PROP_X:
+		if (item->xform == NULL) {
+			g_value_set_double(value, 0);
+		} else if (GTK_OBJECT(gobject)->flags & GANV_ITEM_AFFINE_FULL) {
+			g_value_set_double(value, item->xform[4]);
+		} else {
+			g_value_set_double(value, item->xform[0]);
+		}
+		break;
+
+	case GROUP_PROP_Y:
+		if (item->xform == NULL) {
+			g_value_set_double(value, 0);
+		} else if (GTK_OBJECT(gobject)->flags & GANV_ITEM_AFFINE_FULL) {
+			g_value_set_double(value, item->xform[5]);
+		} else {
+			g_value_set_double(value, item->xform[1]);
+		}
+		break;
+
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(gobject, param_id, pspec);
+		break;
+	}
+}
+
+/* Destroy handler for canvas groups */
+static void
+ganv_group_destroy(GtkObject* object)
+{
+	GanvGroup* group;
+
+	g_return_if_fail(GANV_IS_GROUP(object));
+
+	group = GANV_GROUP(object);
+
+	while (group->item_list) {
+		// child is unref'ed by the child's group_remove().
+		gtk_object_destroy(GTK_OBJECT(group->item_list->data));
+	}
+	if (GTK_OBJECT_CLASS(group_parent_class)->destroy) {
+		(*GTK_OBJECT_CLASS(group_parent_class)->destroy)(object);
+	}
+}
+
+/* Update handler for canvas groups */
+static void
+ganv_group_update(GanvItem* item, double* affine, ArtSVP* clip_path, int flags)
+{
+	GanvGroup* group;
+	GList*     list;
+	GanvItem*  i;
+	ArtDRect   bbox, child_bbox;
+
+	group = GANV_GROUP(item);
+
+	(*group_parent_class->update)(item, affine, clip_path, flags);
+
+	bbox.x0 = 0;
+	bbox.y0 = 0;
+	bbox.x1 = 0;
+	bbox.y1 = 0;
+
+	for (list = group->item_list; list; list = list->next) {
+		i = list->data;
+
+		ganv_item_invoke_update(i, affine, clip_path, flags);
+
+		child_bbox.x0 = i->x1;
+		child_bbox.y0 = i->y1;
+		child_bbox.x1 = i->x2;
+		child_bbox.y1 = i->y2;
+		art_drect_union(&bbox, &bbox, &child_bbox);
+	}
+	item->x1 = bbox.x0;
+	item->y1 = bbox.y0;
+	item->x2 = bbox.x1;
+	item->y2 = bbox.y1;
+}
+
+/* Realize handler for canvas groups */
+static void
+ganv_group_realize(GanvItem* item)
+{
+	GanvGroup* group;
+	GList*     list;
+	GanvItem*  i;
+
+	group = GANV_GROUP(item);
+
+	for (list = group->item_list; list; list = list->next) {
+		i = list->data;
+
+		if (!(i->object.flags & GANV_ITEM_REALIZED)) {
+			(*GANV_ITEM_GET_CLASS(i)->realize)(i);
+		}
+	}
+
+	(*group_parent_class->realize)(item);
+}
+
+/* Unrealize handler for canvas groups */
+static void
+ganv_group_unrealize(GanvItem* item)
+{
+	GanvGroup* group;
+	GList*     list;
+	GanvItem*  i;
+
+	group = GANV_GROUP(item);
+
+	for (list = group->item_list; list; list = list->next) {
+		i = list->data;
+
+		if (i->object.flags & GANV_ITEM_REALIZED) {
+			(*GANV_ITEM_GET_CLASS(i)->unrealize)(i);
+		}
+	}
+
+	(*group_parent_class->unrealize)(item);
+}
+
+/* Map handler for canvas groups */
+static void
+ganv_group_map(GanvItem* item)
+{
+	GanvGroup* group;
+	GList*     list;
+	GanvItem*  i;
+
+	group = GANV_GROUP(item);
+
+	for (list = group->item_list; list; list = list->next) {
+		i = list->data;
+
+		if (!(i->object.flags & GANV_ITEM_MAPPED)) {
+			(*GANV_ITEM_GET_CLASS(i)->map)(i);
+		}
+	}
+
+	(*group_parent_class->map)(item);
+}
+
+/* Unmap handler for canvas groups */
+static void
+ganv_group_unmap(GanvItem* item)
+{
+	GanvGroup* group;
+	GList*     list;
+	GanvItem*  i;
+
+	group = GANV_GROUP(item);
+
+	for (list = group->item_list; list; list = list->next) {
+		i = list->data;
+
+		if (i->object.flags & GANV_ITEM_MAPPED) {
+			(*GANV_ITEM_GET_CLASS(i)->unmap)(i);
+		}
+	}
+
+	(*group_parent_class->unmap)(item);
+}
+
+/* Draw handler for canvas groups */
+static void
+ganv_group_draw(GanvItem* item, GdkDrawable* drawable,
+                int x, int y, int width, int height)
+{
+	GanvGroup* group;
+	GList*     list;
+	GanvItem*  child = NULL;
+
+	group = GANV_GROUP(item);
+
+	for (list = group->item_list; list; list = list->next) {
+		child = list->data;
+
+		if (((child->object.flags & GANV_ITEM_VISIBLE)
+		     && ((child->x1 < (x + width))
+		         && (child->y1 < (y + height))
+		         && (child->x2 > x)
+		         && (child->y2 > y)))
+		    || ((GTK_OBJECT_FLAGS(child) & GANV_ITEM_ALWAYS_REDRAW)
+		        && (child->x1 < child->canvas->redraw_x2)
+		        && (child->y1 < child->canvas->redraw_y2)
+		        && (child->x2 > child->canvas->redraw_x1)
+		        && (child->y2 > child->canvas->redraw_y2))) {
+			if (GANV_ITEM_GET_CLASS(child)->draw) {
+				(*GANV_ITEM_GET_CLASS(child)->draw)(
+				    child, drawable, x, y, width, height);
+			}
+		}
+	}
+}
+
+/* Point handler for canvas groups */
+static double
+ganv_group_point(GanvItem* item, double x, double y, int cx, int cy,
+                 GanvItem** actual_item)
+{
+	GanvGroup* group;
+	GList*     list;
+	GanvItem*  child, * point_item;
+	int        x1, y1, x2, y2;
+	double     gx, gy;
+	double     dist, best;
+	int        has_point;
+
+	group = GANV_GROUP(item);
+
+	x1 = cx - item->canvas->close_enough;
+	y1 = cy - item->canvas->close_enough;
+	x2 = cx + item->canvas->close_enough;
+	y2 = cy + item->canvas->close_enough;
+
+	best         = 0.0;
+	*actual_item = NULL;
+
+	gx = x;
+	gy = y;
+
+	dist = 0.0; /* keep gcc happy */
+
+	for (list = group->item_list; list; list = list->next) {
+		child = list->data;
+
+		if ((child->x1 > x2) || (child->y1 > y2) || (child->x2 < x1) || (child->y2 < y1)) {
+			continue;
+		}
+
+		point_item = NULL; /* cater for incomplete item implementations */
+
+		if ((child->object.flags & GANV_ITEM_VISIBLE)
+		    && GANV_ITEM_GET_CLASS(child)->point) {
+			dist      = ganv_item_invoke_point(child, gx, gy, cx, cy, &point_item);
+			has_point = TRUE;
+		} else {
+			has_point = FALSE;
+		}
+
+		if (has_point
+		    && point_item
+		    && ((int)(dist * item->canvas->pixels_per_unit + 0.5)
+		        <= item->canvas->close_enough)) {
+			best         = dist;
+			*actual_item = point_item;
+		}
+	}
+
+	return best;
+}
+
+/* Bounds handler for canvas groups */
+static void
+ganv_group_bounds(GanvItem* item, double* x1, double* y1, double* x2, double* y2)
+{
+	GanvGroup* group;
+	GanvItem*  child;
+	GList*     list;
+	double     tx1, ty1, tx2, ty2;
+	double     minx, miny, maxx, maxy;
+	int        set;
+
+	group = GANV_GROUP(item);
+
+	/* Get the bounds of the first visible item */
+
+	child = NULL; /* Unnecessary but eliminates a warning. */
+
+	set = FALSE;
+
+	for (list = group->item_list; list; list = list->next) {
+		child = list->data;
+
+		if (child->object.flags & GANV_ITEM_VISIBLE) {
+			set = TRUE;
+			ganv_item_get_bounds(child, &minx, &miny, &maxx, &maxy);
+			break;
+		}
+	}
+
+	/* If there were no visible items, return an empty bounding box */
+
+	if (!set) {
+		*x1 = *y1 = *x2 = *y2 = 0.0;
+		return;
+	}
+
+	/* Now we can grow the bounds using the rest of the items */
+
+	list = list->next;
+
+	for (; list; list = list->next) {
+		child = list->data;
+
+		if (!(child->object.flags & GANV_ITEM_VISIBLE)) {
+			continue;
+		}
+
+		ganv_item_get_bounds(child, &tx1, &ty1, &tx2, &ty2);
+
+		if (tx1 < minx) {
+			minx = tx1;
+		}
+
+		if (ty1 < miny) {
+			miny = ty1;
+		}
+
+		if (tx2 > maxx) {
+			maxx = tx2;
+		}
+
+		if (ty2 > maxy) {
+			maxy = ty2;
+		}
+	}
+
+	*x1 = minx;
+	*y1 = miny;
+	*x2 = maxx;
+	*y2 = maxy;
+}
+
+/* Adds an item to a group */
+static void
+group_add(GanvGroup* group, GanvItem* item)
+{
+	g_object_ref_sink(G_OBJECT(item));
+
+	if (!group->item_list) {
+		group->item_list     = g_list_append(group->item_list, item);
+		group->item_list_end = group->item_list;
+	} else {
+		group->item_list_end = g_list_append(group->item_list_end, item)->next;
+	}
+
+	if (group->item.object.flags & GANV_ITEM_REALIZED) {
+		(*GANV_ITEM_GET_CLASS(item)->realize)(item);
+	}
+
+	if (group->item.object.flags & GANV_ITEM_MAPPED) {
+		(*GANV_ITEM_GET_CLASS(item)->map)(item);
+	}
+
+	g_object_notify(G_OBJECT(item), "parent");
+}
+
+/* Removes an item from a group */
+static void
+group_remove(GanvGroup* group, GanvItem* item)
+{
+	GList* children;
+
+	g_return_if_fail(GANV_IS_GROUP(group));
+	g_return_if_fail(GANV_IS_ITEM(item));
+
+	for (children = group->item_list; children; children = children->next) {
+		if (children->data == item) {
+			if (item->object.flags & GANV_ITEM_MAPPED) {
+				(*GANV_ITEM_GET_CLASS(item)->unmap)(item);
+			}
+
+			if (item->object.flags & GANV_ITEM_REALIZED) {
+				(*GANV_ITEM_GET_CLASS(item)->unrealize)(item);
+			}
+
+			/* Unparent the child */
+
+			item->parent = NULL;
+			g_object_unref(G_OBJECT(item));
+
+			/* Remove it from the list */
+
+			if (children == group->item_list_end) {
+				group->item_list_end = children->prev;
+			}
+
+			group->item_list = g_list_remove_link(group->item_list, children);
+			g_list_free(children);
+			break;
+		}
+	}
+}
+
+/*** GanvCanvasBase ***/
+
+
+enum {
+	DRAW_BACKGROUND,
+	LAST_SIGNAL
+};
+
+static void ganv_canvas_base_class_init(GanvCanvasBaseClass* class);
+static void ganv_canvas_base_init(GanvCanvasBase* canvas);
+static void ganv_canvas_base_destroy(GtkObject* object);
+static void ganv_canvas_base_map(GtkWidget* widget);
+static void ganv_canvas_base_unmap(GtkWidget* widget);
+static void ganv_canvas_base_realize(GtkWidget* widget);
+static void ganv_canvas_base_unrealize(GtkWidget* widget);
+static void ganv_canvas_base_size_allocate(GtkWidget*     widget,
+                                           GtkAllocation* allocation);
+static gint ganv_canvas_base_button(GtkWidget*      widget,
+                                    GdkEventButton* event);
+static gint ganv_canvas_base_motion(GtkWidget*      widget,
+                                    GdkEventMotion* event);
+static gint ganv_canvas_base_expose(GtkWidget*      widget,
+                                    GdkEventExpose* event);
+static gboolean ganv_canvas_base_key(GtkWidget*   widget,
+                                     GdkEventKey* event);
+static gboolean ganv_canvas_base_scroll(GtkWidget*      widget,
+                                        GdkEventScroll* event);
+static gint ganv_canvas_base_crossing(GtkWidget*        widget,
+                                      GdkEventCrossing* event);
+static gint ganv_canvas_base_focus_in(GtkWidget*     widget,
+                                      GdkEventFocus* event);
+static gint ganv_canvas_base_focus_out(GtkWidget*     widget,
+                                       GdkEventFocus* event);
+static void ganv_canvas_base_request_update_real(GanvCanvasBase* canvas);
+static void ganv_canvas_base_draw_background(GanvCanvasBase* canvas,
+                                             GdkDrawable*    drawable,
+                                             int             x,
+                                             int             y,
+                                             int             width,
+                                             int             height);
+
+
+static GtkLayoutClass* canvas_parent_class;
+
+static guint canvas_signals[LAST_SIGNAL];
+
+enum {
+	PROP_FOCUSED_ITEM = 1
+};
+
+G_DEFINE_TYPE(GanvCanvasBase, ganv_canvas_base, GTK_TYPE_LAYOUT)
+
+static void
+ganv_canvas_base_get_property(GObject*    object,
+                              guint       prop_id,
+                              GValue*     value,
+                              GParamSpec* pspec)
+{
+	switch (prop_id) {
+	case PROP_FOCUSED_ITEM:
+		g_value_set_object(value, GANV_CANVAS_BASE(object)->focused_item);
+		break;
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
+		break;
+	}
+}
+
+static void
+ganv_canvas_base_set_property(GObject*      object,
+                              guint         prop_id,
+                              const GValue* value,
+                              GParamSpec*   pspec)
+{
+	switch (prop_id) {
+	case PROP_FOCUSED_ITEM:
+		GANV_CANVAS_BASE(object)->focused_item = g_value_get_object(value);
+		break;
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
+		break;
+	}
+}
+
+/* Class initialization function for GanvCanvasBaseClass */
+static void
+ganv_canvas_base_class_init(GanvCanvasBaseClass* klass)
+{
+	GObjectClass*   gobject_class;
+	GtkObjectClass* object_class;
+	GtkWidgetClass* widget_class;
+
+	gobject_class = (GObjectClass*)klass;
+	object_class  = (GtkObjectClass*)klass;
+	widget_class  = (GtkWidgetClass*)klass;
+
+	canvas_parent_class = g_type_class_peek_parent(klass);
+
+	gobject_class->set_property = ganv_canvas_base_set_property;
+	gobject_class->get_property = ganv_canvas_base_get_property;
+
+	object_class->destroy = ganv_canvas_base_destroy;
+
+	widget_class->map                  = ganv_canvas_base_map;
+	widget_class->unmap                = ganv_canvas_base_unmap;
+	widget_class->realize              = ganv_canvas_base_realize;
+	widget_class->unrealize            = ganv_canvas_base_unrealize;
+	widget_class->size_allocate        = ganv_canvas_base_size_allocate;
+	widget_class->button_press_event   = ganv_canvas_base_button;
+	widget_class->button_release_event = ganv_canvas_base_button;
+	widget_class->motion_notify_event  = ganv_canvas_base_motion;
+	widget_class->expose_event         = ganv_canvas_base_expose;
+	widget_class->key_press_event      = ganv_canvas_base_key;
+	widget_class->key_release_event    = ganv_canvas_base_key;
+	widget_class->enter_notify_event   = ganv_canvas_base_crossing;
+	widget_class->leave_notify_event   = ganv_canvas_base_crossing;
+	widget_class->focus_in_event       = ganv_canvas_base_focus_in;
+	widget_class->focus_out_event      = ganv_canvas_base_focus_out;
+	widget_class->scroll_event         = ganv_canvas_base_scroll;
+
+	klass->draw_background = ganv_canvas_base_draw_background;
+	klass->request_update  = ganv_canvas_base_request_update_real;
+
+	g_object_class_install_property(gobject_class, PROP_FOCUSED_ITEM,
+	                                g_param_spec_object("focused_item", NULL, NULL,
+	                                                    GANV_TYPE_ITEM,
+	                                                    (G_PARAM_READABLE | G_PARAM_WRITABLE)));
+
+	canvas_signals[DRAW_BACKGROUND]
+	    = g_signal_new("draw_background",
+	                   G_TYPE_FROM_CLASS(object_class),
+	                   G_SIGNAL_RUN_LAST,
+	                   G_STRUCT_OFFSET(GanvCanvasBaseClass, draw_background),
+	                   NULL, NULL,
+	                   ganv_marshal_VOID__OBJECT_INT_INT_INT_INT,
+	                   G_TYPE_NONE, 5, GDK_TYPE_DRAWABLE,
+	                   G_TYPE_INT, G_TYPE_INT, G_TYPE_INT, G_TYPE_INT);
+}
+
+/* Callback used when the root item of a canvas is destroyed.  The user should
+ * never ever do this, so we panic if this happens.
+ */
+static void
+panic_root_destroyed(GtkObject* object, gpointer data)
+{
+	g_error("Eeeek, root item %p of canvas %p was destroyed!", (void*)object, data);
+}
+
+/* Object initialization function for GanvCanvasBase */
+static void
+ganv_canvas_base_init(GanvCanvasBase* canvas)
+{
+	GTK_WIDGET_SET_FLAGS(canvas, GTK_CAN_FOCUS);
+
+	canvas->need_update = FALSE;
+	canvas->need_redraw = FALSE;
+	canvas->redraw_area = NULL;
+	canvas->idle_id     = 0;
+
+	canvas->scroll_x1 = 0.0;
+	canvas->scroll_y1 = 0.0;
+	canvas->scroll_x2 = canvas->layout.width;
+	canvas->scroll_y2 = canvas->layout.height;
+
+	canvas->pixels_per_unit = 1.0;
+
+	canvas->pick_event.type       = GDK_LEAVE_NOTIFY;
+	canvas->pick_event.crossing.x = 0;
+	canvas->pick_event.crossing.y = 0;
+
+	canvas->center_scroll_region = TRUE;
+
+	gtk_layout_set_hadjustment(GTK_LAYOUT(canvas), NULL);
+	gtk_layout_set_vadjustment(GTK_LAYOUT(canvas), NULL);
+
+	/* Disable the gtk+ double buffering since the canvas uses it's own. */
+	gtk_widget_set_double_buffered(GTK_WIDGET(canvas), FALSE);
+
+	/* Create the root item as a special case */
+
+	canvas->root         = GANV_ITEM(g_object_new(ganv_group_get_type(), NULL));
+	canvas->root->canvas = canvas;
+
+	g_object_ref_sink(canvas->root);
+
+	canvas->root_destroy_id = g_signal_connect(canvas->root, "destroy",
+	                                           G_CALLBACK(panic_root_destroyed),
+	                                           canvas);
+
+	canvas->need_repick = TRUE;
+}
+
+/* Convenience function to remove the idle handler of a canvas */
+static void
+remove_idle(GanvCanvasBase* canvas)
+{
+	if (canvas->idle_id == 0) {
+		return;
+	}
+
+	g_source_remove(canvas->idle_id);
+	canvas->idle_id = 0;
+}
+
+/* Removes the transient state of the canvas (idle handler, grabs). */
+static void
+shutdown_transients(GanvCanvasBase* canvas)
+{
+	/* We turn off the need_redraw flag, since if the canvas is mapped again
+	 * it will request a redraw anyways.  We do not turn off the need_update
+	 * flag, though, because updates are not queued when the canvas remaps
+	 * itself.
+	 */
+	if (canvas->need_redraw) {
+		canvas->need_redraw = FALSE;
+		art_uta_free(canvas->redraw_area);
+		canvas->redraw_area = NULL;
+		canvas->redraw_x1   = 0;
+		canvas->redraw_y1   = 0;
+		canvas->redraw_x2   = 0;
+		canvas->redraw_y2   = 0;
+	}
+
+	if (canvas->grabbed_item) {
+		canvas->grabbed_item = NULL;
+		gdk_pointer_ungrab(GDK_CURRENT_TIME);
+	}
+
+	remove_idle(canvas);
+}
+
+/* Destroy handler for GanvCanvasBase */
+static void
+ganv_canvas_base_destroy(GtkObject* object)
+{
+	GanvCanvasBase* canvas;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(object));
+
+	/* remember, destroy can be run multiple times! */
+
+	canvas = GANV_CANVAS_BASE(object);
+
+	if (canvas->root_destroy_id) {
+		g_signal_handler_disconnect(canvas->root, canvas->root_destroy_id);
+		canvas->root_destroy_id = 0;
+	}
+	if (canvas->root) {
+		gtk_object_destroy(GTK_OBJECT(canvas->root));
+		g_object_unref(G_OBJECT(canvas->root));
+		canvas->root = NULL;
+	}
+
+	shutdown_transients(canvas);
+
+	if (GTK_OBJECT_CLASS(canvas_parent_class)->destroy) {
+		(*GTK_OBJECT_CLASS(canvas_parent_class)->destroy)(object);
+	}
+}
+
+/**
+ * ganv_canvas_base_new:
+ *
+ * Creates a new empty canvas in non-antialiased mode.
+ *
+ * Return value: A newly-created canvas.
+ **/
+GtkWidget*
+ganv_canvas_base_new(void)
+{
+	return GTK_WIDGET(g_object_new(ganv_canvas_base_get_type(), NULL));
+}
+
+/* Map handler for the canvas */
+static void
+ganv_canvas_base_map(GtkWidget* widget)
+{
+	GanvCanvasBase* canvas;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(widget));
+
+	/* Normal widget mapping stuff */
+
+	if (GTK_WIDGET_CLASS(canvas_parent_class)->map) {
+		(*GTK_WIDGET_CLASS(canvas_parent_class)->map)(widget);
+	}
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	if (canvas->need_update) {
+		add_idle(canvas);
+	}
+
+	/* Map items */
+
+	if (GANV_ITEM_GET_CLASS(canvas->root)->map) {
+		(*GANV_ITEM_GET_CLASS(canvas->root)->map)(canvas->root);
+	}
+}
+
+/* Unmap handler for the canvas */
+static void
+ganv_canvas_base_unmap(GtkWidget* widget)
+{
+	GanvCanvasBase* canvas;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(widget));
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	shutdown_transients(canvas);
+
+	/* Unmap items */
+
+	if (GANV_ITEM_GET_CLASS(canvas->root)->unmap) {
+		(*GANV_ITEM_GET_CLASS(canvas->root)->unmap)(canvas->root);
+	}
+
+	/* Normal widget unmapping stuff */
+
+	if (GTK_WIDGET_CLASS(canvas_parent_class)->unmap) {
+		(*GTK_WIDGET_CLASS(canvas_parent_class)->unmap)(widget);
+	}
+}
+
+/* Realize handler for the canvas */
+static void
+ganv_canvas_base_realize(GtkWidget* widget)
+{
+	GanvCanvasBase* canvas;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(widget));
+
+	/* Normal widget realization stuff */
+
+	if (GTK_WIDGET_CLASS(canvas_parent_class)->realize) {
+		(*GTK_WIDGET_CLASS(canvas_parent_class)->realize)(widget);
+	}
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	gdk_window_set_events(canvas->layout.bin_window,
+	                      (gdk_window_get_events(canvas->layout.bin_window)
+	                       | GDK_EXPOSURE_MASK
+	                       | GDK_BUTTON_PRESS_MASK
+	                       | GDK_BUTTON_RELEASE_MASK
+	                       | GDK_POINTER_MOTION_MASK
+	                       | GDK_KEY_PRESS_MASK
+	                       | GDK_KEY_RELEASE_MASK
+	                       | GDK_ENTER_NOTIFY_MASK
+	                       | GDK_LEAVE_NOTIFY_MASK
+	                       | GDK_FOCUS_CHANGE_MASK));
+
+	/* Create our own temporary pixmap gc and realize all the items */
+
+	canvas->pixmap_gc = gdk_gc_new(canvas->layout.bin_window);
+
+	(*GANV_ITEM_GET_CLASS(canvas->root)->realize)(canvas->root);
+}
+
+/* Unrealize handler for the canvas */
+static void
+ganv_canvas_base_unrealize(GtkWidget* widget)
+{
+	GanvCanvasBase* canvas;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(widget));
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	shutdown_transients(canvas);
+
+	/* Unrealize items and parent widget */
+
+	(*GANV_ITEM_GET_CLASS(canvas->root)->unrealize)(canvas->root);
+
+	g_object_unref(canvas->pixmap_gc);
+	canvas->pixmap_gc = NULL;
+
+	if (GTK_WIDGET_CLASS(canvas_parent_class)->unrealize) {
+		(*GTK_WIDGET_CLASS(canvas_parent_class)->unrealize)(widget);
+	}
+}
+
+/* Handles scrolling of the canvas.  Adjusts the scrolling and zooming offset to
+ * keep as much as possible of the canvas scrolling region in view.
+ */
+static void
+scroll_to(GanvCanvasBase* canvas, int cx, int cy)
+{
+	int scroll_width, scroll_height;
+	int right_limit, bottom_limit;
+	int old_zoom_xofs, old_zoom_yofs;
+	int changed_x = FALSE, changed_y = FALSE;
+	int canvas_width, canvas_height;
+
+	canvas_width  = GTK_WIDGET(canvas)->allocation.width;
+	canvas_height = GTK_WIDGET(canvas)->allocation.height;
+
+	scroll_width = floor((canvas->scroll_x2 - canvas->scroll_x1) * canvas->pixels_per_unit
+	                     + 0.5);
+	scroll_height = floor((canvas->scroll_y2 - canvas->scroll_y1) * canvas->pixels_per_unit
+	                      + 0.5);
+
+	right_limit  = scroll_width - canvas_width;
+	bottom_limit = scroll_height - canvas_height;
+
+	old_zoom_xofs = canvas->zoom_xofs;
+	old_zoom_yofs = canvas->zoom_yofs;
+
+	if (right_limit < 0) {
+		cx = 0;
+
+		if (canvas->center_scroll_region) {
+			canvas->zoom_xofs = (canvas_width - scroll_width) / 2;
+			scroll_width      = canvas_width;
+		} else {
+			canvas->zoom_xofs = 0;
+		}
+	} else if (cx < 0) {
+		cx                = 0;
+		canvas->zoom_xofs = 0;
+	} else if (cx > right_limit) {
+		cx                = right_limit;
+		canvas->zoom_xofs = 0;
+	} else {
+		canvas->zoom_xofs = 0;
+	}
+
+	if (bottom_limit < 0) {
+		cy = 0;
+
+		if (canvas->center_scroll_region) {
+			canvas->zoom_yofs = (canvas_height - scroll_height) / 2;
+			scroll_height     = canvas_height;
+		} else {
+			canvas->zoom_yofs = 0;
+		}
+	} else if (cy < 0) {
+		cy                = 0;
+		canvas->zoom_yofs = 0;
+	} else if (cy > bottom_limit) {
+		cy                = bottom_limit;
+		canvas->zoom_yofs = 0;
+	} else {
+		canvas->zoom_yofs = 0;
+	}
+
+	if ((canvas->zoom_xofs != old_zoom_xofs) || (canvas->zoom_yofs != old_zoom_yofs)) {
+		/* This can only occur, if either canvas size or widget size changes */
+		/* So I think we can request full redraw here */
+		/* The reason is, that coverage UTA will be invalidated by offset change */
+		/* fixme: Strictly this is not correct - we have to remove our own idle (Lauris) */
+		/* More stuff - we have to mark root as needing fresh affine (Lauris) */
+		if (!(canvas->root->object.flags & GANV_ITEM_NEED_AFFINE)) {
+			canvas->root->object.flags |= GANV_ITEM_NEED_AFFINE;
+			ganv_canvas_base_request_update(canvas);
+		}
+		gtk_widget_queue_draw(GTK_WIDGET(canvas));
+	}
+
+	if (canvas->layout.hadjustment && ( ((int)canvas->layout.hadjustment->value) != cx) ) {
+		canvas->layout.hadjustment->value = cx;
+		changed_x                         = TRUE;
+	}
+
+	if (canvas->layout.vadjustment && ( ((int)canvas->layout.vadjustment->value) != cy) ) {
+		canvas->layout.vadjustment->value = cy;
+		changed_y                         = TRUE;
+	}
+
+	if ((scroll_width != (int)canvas->layout.width)
+	    || (scroll_height != (int)canvas->layout.height)) {
+		gtk_layout_set_size(GTK_LAYOUT(canvas), scroll_width, scroll_height);
+	}
+
+	/* Signal GtkLayout that it should do a redraw. */
+
+	if (changed_x) {
+		g_signal_emit_by_name(canvas->layout.hadjustment, "value_changed");
+	}
+
+	if (changed_y) {
+		g_signal_emit_by_name(canvas->layout.vadjustment, "value_changed");
+	}
+}
+
+/* Size allocation handler for the canvas */
+static void
+ganv_canvas_base_size_allocate(GtkWidget* widget, GtkAllocation* allocation)
+{
+	GanvCanvasBase* canvas;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(widget));
+	g_return_if_fail(allocation != NULL);
+
+	if (GTK_WIDGET_CLASS(canvas_parent_class)->size_allocate) {
+		(*GTK_WIDGET_CLASS(canvas_parent_class)->size_allocate)(widget, allocation);
+	}
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	/* Recenter the view, if appropriate */
+
+	canvas->layout.hadjustment->page_size      = allocation->width;
+	canvas->layout.hadjustment->page_increment = allocation->width / 2;
+
+	canvas->layout.vadjustment->page_size      = allocation->height;
+	canvas->layout.vadjustment->page_increment = allocation->height / 2;
+
+	scroll_to(canvas,
+	          canvas->layout.hadjustment->value,
+	          canvas->layout.vadjustment->value);
+
+	g_signal_emit_by_name(canvas->layout.hadjustment, "changed");
+	g_signal_emit_by_name(canvas->layout.vadjustment, "changed");
+}
+
+/* Emits an event for an item in the canvas, be it the current item, grabbed
+ * item, or focused item, as appropriate.
+ */
+
+static int
+emit_event(GanvCanvasBase* canvas, GdkEvent* event)
+{
+	GdkEvent* ev;
+	gint      finished;
+	GanvItem* item;
+	GanvItem* parent;
+	guint     mask;
+
+	/* Perform checks for grabbed items */
+
+	if (canvas->grabbed_item
+	    && !is_descendant(canvas->current_item, canvas->grabbed_item)) {
+		/* I think this warning is annoying and I don't know what it's for
+		 * so I'll disable it for now.
+		 */
+		/*                g_warning ("emit_event() returning FALSE!\n");*/
+		return FALSE;
+	}
+
+	if (canvas->grabbed_item) {
+		switch (event->type) {
+		case GDK_ENTER_NOTIFY:
+			mask = GDK_ENTER_NOTIFY_MASK;
+			break;
+
+		case GDK_LEAVE_NOTIFY:
+			mask = GDK_LEAVE_NOTIFY_MASK;
+			break;
+
+		case GDK_MOTION_NOTIFY:
+			mask = GDK_POINTER_MOTION_MASK;
+			break;
+
+		case GDK_BUTTON_PRESS:
+		case GDK_2BUTTON_PRESS:
+		case GDK_3BUTTON_PRESS:
+			mask = GDK_BUTTON_PRESS_MASK;
+			break;
+
+		case GDK_BUTTON_RELEASE:
+			mask = GDK_BUTTON_RELEASE_MASK;
+			break;
+
+		case GDK_KEY_PRESS:
+			mask = GDK_KEY_PRESS_MASK;
+			break;
+
+		case GDK_KEY_RELEASE:
+			mask = GDK_KEY_RELEASE_MASK;
+			break;
+
+		case GDK_SCROLL:
+			mask = GDK_SCROLL_MASK;
+			break;
+
+		default:
+			mask = 0;
+			break;
+		}
+
+		if (!(mask & canvas->grabbed_event_mask)) {
+			return FALSE;
+		}
+	}
+
+	/* Convert to world coordinates -- we have two cases because of diferent
+	 * offsets of the fields in the event structures.
+	 */
+
+	ev = gdk_event_copy(event);
+
+	switch (ev->type) {
+	case GDK_ENTER_NOTIFY:
+	case GDK_LEAVE_NOTIFY:
+		ganv_canvas_base_window_to_world(canvas,
+		                                 ev->crossing.x, ev->crossing.y,
+		                                 &ev->crossing.x, &ev->crossing.y);
+		break;
+
+	case GDK_MOTION_NOTIFY:
+	case GDK_BUTTON_PRESS:
+	case GDK_2BUTTON_PRESS:
+	case GDK_3BUTTON_PRESS:
+	case GDK_BUTTON_RELEASE:
+		ganv_canvas_base_window_to_world(canvas,
+		                                 ev->motion.x, ev->motion.y,
+		                                 &ev->motion.x, &ev->motion.y);
+		break;
+
+	default:
+		break;
+	}
+
+	/* Choose where we send the event */
+
+	item = canvas->current_item;
+
+	if (canvas->focused_item
+	    && ((event->type == GDK_KEY_PRESS)
+	        || (event->type == GDK_KEY_RELEASE)
+	        || (event->type == GDK_FOCUS_CHANGE))) {
+		item = canvas->focused_item;
+	}
+
+	/* The event is propagated up the hierarchy (for if someone connected to
+	 * a group instead of a leaf event), and emission is stopped if a
+	 * handler returns TRUE, just like for GtkWidget events.
+	 */
+
+	finished = FALSE;
+
+	while (item && !finished) {
+		g_object_ref(G_OBJECT(item));
+
+		g_signal_emit(item, item_signals[ITEM_EVENT], 0,
+		              ev, &finished);
+
+		parent = item->parent;
+		g_object_unref(G_OBJECT(item));
+
+		item = parent;
+	}
+
+	gdk_event_free(ev);
+
+	return finished;
+}
+
+/* Re-picks the current item in the canvas, based on the event's coordinates.
+ * Also emits enter/leave events for items as appropriate.
+ */
+static int
+pick_current_item(GanvCanvasBase* canvas, GdkEvent* event)
+{
+	int    button_down;
+	double x, y;
+	int    cx, cy;
+	int    retval;
+
+	retval = FALSE;
+
+	/* If a button is down, we'll perform enter and leave events on the
+	 * current item, but not enter on any other item.  This is more or less
+	 * like X pointer grabbing for canvas items.
+	 */
+	button_down = canvas->state & (GDK_BUTTON1_MASK
+	                               | GDK_BUTTON2_MASK
+	                               | GDK_BUTTON3_MASK
+	                               | GDK_BUTTON4_MASK
+	                               | GDK_BUTTON5_MASK);
+	if (!button_down) {
+		canvas->left_grabbed_item = FALSE;
+	}
+
+	/* Save the event in the canvas.  This is used to synthesize enter and
+	 * leave events in case the current item changes.  It is also used to
+	 * re-pick the current item if the current one gets deleted.  Also,
+	 * synthesize an enter event.
+	 */
+	if (event != &canvas->pick_event) {
+		if ((event->type == GDK_MOTION_NOTIFY) || (event->type == GDK_BUTTON_RELEASE)) {
+			/* these fields have the same offsets in both types of events */
+
+			canvas->pick_event.crossing.type       = GDK_ENTER_NOTIFY;
+			canvas->pick_event.crossing.window     = event->motion.window;
+			canvas->pick_event.crossing.send_event = event->motion.send_event;
+			canvas->pick_event.crossing.subwindow  = NULL;
+			canvas->pick_event.crossing.x          = event->motion.x;
+			canvas->pick_event.crossing.y          = event->motion.y;
+			canvas->pick_event.crossing.mode       = GDK_CROSSING_NORMAL;
+			canvas->pick_event.crossing.detail     = GDK_NOTIFY_NONLINEAR;
+			canvas->pick_event.crossing.focus      = FALSE;
+			canvas->pick_event.crossing.state      = event->motion.state;
+
+			/* these fields don't have the same offsets in both types of events */
+
+			if (event->type == GDK_MOTION_NOTIFY) {
+				canvas->pick_event.crossing.x_root = event->motion.x_root;
+				canvas->pick_event.crossing.y_root = event->motion.y_root;
+			} else {
+				canvas->pick_event.crossing.x_root = event->button.x_root;
+				canvas->pick_event.crossing.y_root = event->button.y_root;
+			}
+		} else {
+			canvas->pick_event = *event;
+		}
+	}
+
+	/* Don't do anything else if this is a recursive call */
+
+	if (canvas->in_repick) {
+		return retval;
+	}
+
+	/* LeaveNotify means that there is no current item, so we don't look for one */
+
+	if (canvas->pick_event.type != GDK_LEAVE_NOTIFY) {
+		/* these fields don't have the same offsets in both types of events */
+
+		if (canvas->pick_event.type == GDK_ENTER_NOTIFY) {
+			x = canvas->pick_event.crossing.x - canvas->zoom_xofs;
+			y = canvas->pick_event.crossing.y - canvas->zoom_yofs;
+		} else {
+			x = canvas->pick_event.motion.x - canvas->zoom_xofs;
+			y = canvas->pick_event.motion.y - canvas->zoom_yofs;
+		}
+
+		/* canvas pixel coords */
+
+		cx = (int)(x + 0.5);
+		cy = (int)(y + 0.5);
+
+		/* world coords */
+
+		x = canvas->scroll_x1 + x / canvas->pixels_per_unit;
+		y = canvas->scroll_y1 + y / canvas->pixels_per_unit;
+
+		/* find the closest item */
+
+		if (canvas->root->object.flags & GANV_ITEM_VISIBLE) {
+			ganv_item_invoke_point(canvas->root, x, y, cx, cy,
+			                       &canvas->new_current_item);
+		} else {
+			canvas->new_current_item = NULL;
+		}
+	} else {
+		canvas->new_current_item = NULL;
+	}
+
+	if ((canvas->new_current_item == canvas->current_item) && !canvas->left_grabbed_item) {
+		return retval; /* current item did not change */
+
+	}
+	/* Synthesize events for old and new current items */
+
+	if ((canvas->new_current_item != canvas->current_item)
+	    && (canvas->current_item != NULL)
+	    && !canvas->left_grabbed_item) {
+		GdkEvent new_event;
+
+		new_event      = canvas->pick_event;
+		new_event.type = GDK_LEAVE_NOTIFY;
+
+		new_event.crossing.detail    = GDK_NOTIFY_ANCESTOR;
+		new_event.crossing.subwindow = NULL;
+		canvas->in_repick            = TRUE;
+		retval                       = emit_event(canvas, &new_event);
+		canvas->in_repick            = FALSE;
+	}
+
+	/* new_current_item may have been set to NULL during the call to emit_event() above */
+
+	if ((canvas->new_current_item != canvas->current_item) && button_down) {
+		canvas->left_grabbed_item = TRUE;
+		return retval;
+	}
+
+	/* Handle the rest of cases */
+
+	canvas->left_grabbed_item = FALSE;
+	canvas->current_item      = canvas->new_current_item;
+
+	if (canvas->current_item != NULL) {
+		GdkEvent new_event;
+
+		new_event                    = canvas->pick_event;
+		new_event.type               = GDK_ENTER_NOTIFY;
+		new_event.crossing.detail    = GDK_NOTIFY_ANCESTOR;
+		new_event.crossing.subwindow = NULL;
+		retval                       = emit_event(canvas, &new_event);
+	}
+
+	return retval;
+}
+
+/* Button event handler for the canvas */
+static gint
+ganv_canvas_base_button(GtkWidget* widget, GdkEventButton* event)
+{
+	GanvCanvasBase* canvas;
+	int             mask;
+	int             retval;
+
+	g_return_val_if_fail(GANV_IS_CANVAS_BASE(widget), FALSE);
+	g_return_val_if_fail(event != NULL, FALSE);
+
+	retval = FALSE;
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	/*
+	 * dispatch normally regardless of the event's window if an item has
+	 * has a pointer grab in effect
+	 */
+	if (!canvas->grabbed_item && ( event->window != canvas->layout.bin_window) ) {
+		return retval;
+	}
+
+	switch (event->button) {
+	case 1:
+		mask = GDK_BUTTON1_MASK;
+		break;
+	case 2:
+		mask = GDK_BUTTON2_MASK;
+		break;
+	case 3:
+		mask = GDK_BUTTON3_MASK;
+		break;
+	case 4:
+		mask = GDK_BUTTON4_MASK;
+		break;
+	case 5:
+		mask = GDK_BUTTON5_MASK;
+		break;
+	default:
+		mask = 0;
+	}
+
+	switch (event->type) {
+	case GDK_BUTTON_PRESS:
+	case GDK_2BUTTON_PRESS:
+	case GDK_3BUTTON_PRESS:
+		/* Pick the current item as if the button were not pressed, and
+		 * then process the event.
+		 */
+		canvas->state = event->state;
+		pick_current_item(canvas, (GdkEvent*)event);
+		canvas->state ^= mask;
+		retval         = emit_event(canvas, (GdkEvent*)event);
+		break;
+
+	case GDK_BUTTON_RELEASE:
+		/* Process the event as if the button were pressed, then repick
+		 * after the button has been released
+		 */
+		canvas->state = event->state;
+		retval        = emit_event(canvas, (GdkEvent*)event);
+		event->state ^= mask;
+		canvas->state = event->state;
+		pick_current_item(canvas, (GdkEvent*)event);
+		event->state ^= mask;
+		break;
+
+	default:
+		g_assert_not_reached();
+	}
+
+	return retval;
+}
+
+/* Motion event handler for the canvas */
+static gint
+ganv_canvas_base_motion(GtkWidget* widget, GdkEventMotion* event)
+{
+	GanvCanvasBase* canvas;
+
+	g_return_val_if_fail(GANV_IS_CANVAS_BASE(widget), FALSE);
+	g_return_val_if_fail(event != NULL, FALSE);
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	if (event->window != canvas->layout.bin_window) {
+		return FALSE;
+	}
+
+	canvas->state = event->state;
+	pick_current_item(canvas, (GdkEvent*)event);
+	return emit_event(canvas, (GdkEvent*)event);
+}
+
+static gboolean
+ganv_canvas_base_scroll(GtkWidget* widget, GdkEventScroll* event)
+{
+	GanvCanvasBase* canvas;
+
+	g_return_val_if_fail(GANV_IS_CANVAS_BASE(widget), FALSE);
+	g_return_val_if_fail(event != NULL, FALSE);
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	if (event->window != canvas->layout.bin_window) {
+		return FALSE;
+	}
+
+	canvas->state = event->state;
+	pick_current_item(canvas, (GdkEvent*)event);
+	return emit_event(canvas, (GdkEvent*)event);
+}
+
+/* Key event handler for the canvas */
+static gboolean
+ganv_canvas_base_key(GtkWidget* widget, GdkEventKey* event)
+{
+	GanvCanvasBase* canvas;
+
+	g_return_val_if_fail(GANV_IS_CANVAS_BASE(widget), FALSE);
+	g_return_val_if_fail(event != NULL, FALSE);
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	if (!emit_event(canvas, (GdkEvent*)event)) {
+		GtkWidgetClass* widget_class;
+
+		widget_class = GTK_WIDGET_CLASS(canvas_parent_class);
+
+		if (event->type == GDK_KEY_PRESS) {
+			if (widget_class->key_press_event) {
+				return (*widget_class->key_press_event)(widget, event);
+			}
+		} else if (event->type == GDK_KEY_RELEASE) {
+			if (widget_class->key_release_event) {
+				return (*widget_class->key_release_event)(widget, event);
+			}
+		} else {
+			g_assert_not_reached();
+		}
+
+		return FALSE;
+	} else {
+		return TRUE;
+	}
+}
+
+/* Crossing event handler for the canvas */
+static gint
+ganv_canvas_base_crossing(GtkWidget* widget, GdkEventCrossing* event)
+{
+	GanvCanvasBase* canvas;
+
+	g_return_val_if_fail(GANV_IS_CANVAS_BASE(widget), FALSE);
+	g_return_val_if_fail(event != NULL, FALSE);
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	if (event->window != canvas->layout.bin_window) {
+		return FALSE;
+	}
+
+	canvas->state = event->state;
+	return pick_current_item(canvas, (GdkEvent*)event);
+}
+
+/* Focus in handler for the canvas */
+static gint
+ganv_canvas_base_focus_in(GtkWidget* widget, GdkEventFocus* event)
+{
+	GanvCanvasBase* canvas;
+
+	GTK_WIDGET_SET_FLAGS(widget, GTK_HAS_FOCUS);
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	if (canvas->focused_item) {
+		return emit_event(canvas, (GdkEvent*)event);
+	} else {
+		return FALSE;
+	}
+}
+
+/* Focus out handler for the canvas */
+static gint
+ganv_canvas_base_focus_out(GtkWidget* widget, GdkEventFocus* event)
+{
+	GanvCanvasBase* canvas;
+
+	GTK_WIDGET_UNSET_FLAGS(widget, GTK_HAS_FOCUS);
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	if (canvas->focused_item) {
+		return emit_event(canvas, (GdkEvent*)event);
+	} else {
+		return FALSE;
+	}
+}
+
+#define REDRAW_QUANTUM_SIZE 512
+
+static void
+ganv_canvas_base_paint_rect(GanvCanvasBase* canvas, gint x0, gint y0, gint x1, gint y1)
+{
+	GtkWidget* widget;
+	gint       draw_x1, draw_y1;
+	gint       draw_x2, draw_y2;
+	gint       draw_width, draw_height;
+
+	g_return_if_fail(!canvas->need_update);
+
+	widget = GTK_WIDGET(canvas);
+
+	draw_x1 = MAX(x0, canvas->layout.hadjustment->value - canvas->zoom_xofs);
+	draw_y1 = MAX(y0, canvas->layout.vadjustment->value - canvas->zoom_yofs);
+	draw_x2 = MIN(draw_x1 + GTK_WIDGET(canvas)->allocation.width, x1);
+	draw_y2 = MIN(draw_y1 + GTK_WIDGET(canvas)->allocation.height, y1);
+
+	draw_width  = draw_x2 - draw_x1;
+	draw_height = draw_y2 - draw_y1;
+
+	if (( draw_width < 1) || ( draw_height < 1) ) {
+		return;
+	}
+
+	canvas->redraw_x1 = draw_x1;
+	canvas->redraw_y1 = draw_y1;
+	canvas->redraw_x2 = draw_x2;
+	canvas->redraw_y2 = draw_y2;
+	canvas->draw_xofs = draw_x1;
+	canvas->draw_yofs = draw_y1;
+
+	GdkPixmap* pixmap;
+
+	pixmap = gdk_pixmap_new(canvas->layout.bin_window,
+	                        draw_width, draw_height,
+	                        gtk_widget_get_visual(widget)->depth);
+
+	g_signal_emit(G_OBJECT(canvas), canvas_signals[DRAW_BACKGROUND], 0, pixmap,
+	              draw_x1, draw_y1, draw_width, draw_height);
+
+	if (canvas->root->object.flags & GANV_ITEM_VISIBLE) {
+		(*GANV_ITEM_GET_CLASS(canvas->root)->draw)(
+		    canvas->root, pixmap,
+		    draw_x1, draw_y1,
+		    draw_width, draw_height);
+	}
+
+	/* Copy the pixmap to the window and clean up */
+
+	gdk_draw_drawable(canvas->layout.bin_window,
+	                  canvas->pixmap_gc,
+	                  pixmap,
+	                  0, 0,
+	                  draw_x1 + canvas->zoom_xofs,
+	                  draw_y1 + canvas->zoom_yofs,
+	                  draw_width, draw_height);
+
+	g_object_unref(pixmap);
+}
+
+/* Expose handler for the canvas */
+static gint
+ganv_canvas_base_expose(GtkWidget* widget, GdkEventExpose* event)
+{
+	GanvCanvasBase* canvas;
+	GdkRectangle*   rects;
+	gint            n_rects;
+	int             i;
+
+	canvas = GANV_CANVAS_BASE(widget);
+
+	if (!GTK_WIDGET_DRAWABLE(widget) || (event->window != canvas->layout.bin_window)) {
+		return FALSE;
+	}
+
+#ifdef VERBOSE
+	g_print("Expose\n");
+#endif
+
+	gdk_region_get_rectangles(event->region, &rects, &n_rects);
+
+	for (i = 0; i < n_rects; i++) {
+		ArtIRect rect;
+
+		rect.x0 = rects[i].x - canvas->zoom_xofs;
+		rect.y0 = rects[i].y - canvas->zoom_yofs;
+		rect.x1 = rects[i].x + rects[i].width - canvas->zoom_xofs;
+		rect.y1 = rects[i].y + rects[i].height - canvas->zoom_yofs;
+
+		if (canvas->need_update || canvas->need_redraw) {
+			ArtUta* uta;
+
+			/* Update or drawing is scheduled, so just mark exposed area as dirty */
+			uta = art_uta_from_irect(&rect);
+			ganv_canvas_base_request_redraw_uta(canvas, uta);
+		} else {
+			/* No pending updates, draw exposed area immediately */
+			ganv_canvas_base_paint_rect(canvas, rect.x0, rect.y0, rect.x1, rect.y1);
+
+			/* And call expose on parent container class */
+			if (GTK_WIDGET_CLASS(canvas_parent_class)->expose_event) {
+				(*GTK_WIDGET_CLASS(canvas_parent_class)->expose_event)(
+				    widget, event);
+			}
+		}
+	}
+
+	g_free(rects);
+
+	return FALSE;
+}
+
+/* Repaints the areas in the canvas that need it */
+static void
+paint(GanvCanvasBase* canvas)
+{
+	ArtIRect*  rects;
+	gint       n_rects, i;
+	ArtIRect   visible_rect;
+	GdkRegion* region;
+
+	/* Extract big rectangles from the microtile array */
+
+	rects = art_rect_list_from_uta(canvas->redraw_area,
+	                               REDRAW_QUANTUM_SIZE, REDRAW_QUANTUM_SIZE,
+	                               &n_rects);
+
+	art_uta_free(canvas->redraw_area);
+	canvas->redraw_area = NULL;
+	canvas->need_redraw = FALSE;
+
+	/* Turn those rectangles into a GdkRegion for exposing */
+
+	visible_rect.x0 = canvas->layout.hadjustment->value - canvas->zoom_xofs;
+	visible_rect.y0 = canvas->layout.vadjustment->value - canvas->zoom_yofs;
+	visible_rect.x1 = visible_rect.x0 + GTK_WIDGET(canvas)->allocation.width;
+	visible_rect.y1 = visible_rect.y0 + GTK_WIDGET(canvas)->allocation.height;
+
+	region = gdk_region_new();
+
+	for (i = 0; i < n_rects; i++) {
+		ArtIRect clipped;
+
+		art_irect_intersect(&clipped, &visible_rect, rects + i);
+		if (!art_irect_empty(&clipped)) {
+			GdkRectangle gdkrect;
+
+			gdkrect.x      = clipped.x0 + canvas->zoom_xofs;
+			gdkrect.y      = clipped.y0 + canvas->zoom_yofs;
+			gdkrect.width  = clipped.x1 - clipped.x0;
+			gdkrect.height = clipped.y1 - clipped.y0;
+
+			region = gdk_region_rectangle(&gdkrect);
+			gdk_window_invalidate_region(canvas->layout.bin_window, region, FALSE);
+			gdk_region_destroy(region);
+		}
+	}
+
+	art_free(rects);
+
+	canvas->redraw_x1 = 0;
+	canvas->redraw_y1 = 0;
+	canvas->redraw_x2 = 0;
+	canvas->redraw_y2 = 0;
+}
+
+static void
+ganv_canvas_base_draw_background(GanvCanvasBase* canvas, GdkDrawable* drawable,
+                                 int x, int y, int width, int height)
+{
+	/* By default, we use the style background. */
+	gdk_gc_set_foreground(canvas->pixmap_gc,
+	                      &GTK_WIDGET(canvas)->style->bg[GTK_STATE_NORMAL]);
+	gdk_draw_rectangle(drawable,
+	                   canvas->pixmap_gc,
+	                   TRUE,
+	                   0, 0,
+	                   width, height);
+}
+
+static void
+do_update(GanvCanvasBase* canvas)
+{
+	/* Cause the update if necessary */
+
+update_again:
+	if (canvas->need_update) {
+		gdouble w2cpx[6];
+
+		/* We start updating root with w2cpx affine */
+		w2cpx[0] = canvas->pixels_per_unit;
+		w2cpx[1] = 0.0;
+		w2cpx[2] = 0.0;
+		w2cpx[3] = canvas->pixels_per_unit;
+		w2cpx[4] = -canvas->scroll_x1 * canvas->pixels_per_unit;
+		w2cpx[5] = -canvas->scroll_y1 * canvas->pixels_per_unit;
+
+		ganv_item_invoke_update(canvas->root, w2cpx, NULL, 0);
+
+		canvas->need_update = FALSE;
+	}
+
+	/* Pick new current item */
+
+	while (canvas->need_repick) {
+		canvas->need_repick = FALSE;
+		pick_current_item(canvas, &canvas->pick_event);
+	}
+
+	/* it is possible that during picking we emitted an event in which
+	   the user then called some function which then requested update
+	   of something.  Without this we'd be left in a state where
+	   need_update would have been left TRUE and the canvas would have
+	   been left unpainted. */
+	if (canvas->need_update) {
+		goto update_again;
+	}
+
+	/* Paint if able to */
+
+	if (GTK_WIDGET_DRAWABLE(canvas) && canvas->need_redraw) {
+		paint(canvas);
+	}
+}
+
+/* Idle handler for the canvas.  It deals with pending updates and redraws. */
+static gboolean
+idle_handler(gpointer data)
+{
+	GanvCanvasBase* canvas;
+
+	GDK_THREADS_ENTER();
+
+	canvas = GANV_CANVAS_BASE(data);
+
+	do_update(canvas);
+
+	/* Reset idle id */
+	canvas->idle_id = 0;
+
+	GDK_THREADS_LEAVE();
+
+	return FALSE;
+}
+
+/* Convenience function to add an idle handler to a canvas */
+static void
+add_idle(GanvCanvasBase* canvas)
+{
+	g_assert(canvas->need_update || canvas->need_redraw);
+
+	if (!canvas->idle_id) {
+		canvas->idle_id = g_idle_add_full(CANVAS_IDLE_PRIORITY,
+		                                  idle_handler,
+		                                  canvas,
+		                                  NULL);
+	}
+
+	/*      canvas->idle_id = gtk_idle_add (idle_handler, canvas); */
+}
+
+/**
+ * ganv_canvas_base_root:
+ * @canvas: A canvas.
+ *
+ * Queries the root group of a canvas.
+ *
+ * Return value: The root group of the specified canvas.
+ **/
+GanvGroup*
+ganv_canvas_base_root(GanvCanvasBase* canvas)
+{
+	g_return_val_if_fail(GANV_IS_CANVAS_BASE(canvas), NULL);
+
+	return GANV_GROUP(canvas->root);
+}
+
+/**
+ * ganv_canvas_base_set_scroll_region:
+ * @canvas: A canvas.
+ * @x1: Leftmost limit of the scrolling region.
+ * @y1: Upper limit of the scrolling region.
+ * @x2: Rightmost limit of the scrolling region.
+ * @y2: Lower limit of the scrolling region.
+ *
+ * Sets the scrolling region of a canvas to the specified rectangle.  The canvas
+ * will then be able to scroll only within this region.  The view of the canvas
+ * is adjusted as appropriate to display as much of the new region as possible.
+ **/
+void
+ganv_canvas_base_set_scroll_region(GanvCanvasBase* canvas, double x1, double y1, double x2,
+                                   double y2)
+{
+	double wxofs, wyofs;
+	int    xofs, yofs;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	/*
+	 * Set the new scrolling region.  If possible, do not move the visible contents of the
+	 * canvas.
+	 */
+
+	ganv_canvas_base_c2w(canvas,
+	                     GTK_LAYOUT(canvas)->hadjustment->value + canvas->zoom_xofs,
+	                     GTK_LAYOUT(canvas)->vadjustment->value + canvas->zoom_yofs,
+	                     /*canvas->zoom_xofs,
+	                        canvas->zoom_yofs,*/
+	                     &wxofs, &wyofs);
+
+	canvas->scroll_x1 = x1;
+	canvas->scroll_y1 = y1;
+	canvas->scroll_x2 = x2;
+	canvas->scroll_y2 = y2;
+
+	ganv_canvas_base_w2c(canvas, wxofs, wyofs, &xofs, &yofs);
+
+	scroll_to(canvas, xofs, yofs);
+
+	canvas->need_repick = TRUE;
+#if 0
+	/* todo: should be requesting update */
+	(*GANV_ITEM_CLASS(canvas->root->object.klass)->update)(
+	    canvas->root, NULL, NULL, 0);
+#endif
+}
+
+/**
+ * ganv_canvas_base_get_scroll_region:
+ * @canvas: A canvas.
+ * @x1: Leftmost limit of the scrolling region (return value).
+ * @y1: Upper limit of the scrolling region (return value).
+ * @x2: Rightmost limit of the scrolling region (return value).
+ * @y2: Lower limit of the scrolling region (return value).
+ *
+ * Queries the scrolling region of a canvas.
+ **/
+void
+ganv_canvas_base_get_scroll_region(GanvCanvasBase* canvas, double* x1, double* y1, double* x2,
+                                   double* y2)
+{
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	if (x1) {
+		*x1 = canvas->scroll_x1;
+	}
+
+	if (y1) {
+		*y1 = canvas->scroll_y1;
+	}
+
+	if (x2) {
+		*x2 = canvas->scroll_x2;
+	}
+
+	if (y2) {
+		*y2 = canvas->scroll_y2;
+	}
+}
+
+/**
+ * ganv_canvas_base_set_center_scroll_region:
+ * @canvas: A canvas.
+ * @center_scroll_region: Whether to center the scrolling region in the canvas
+ * window when it is smaller than the canvas' allocation.
+ *
+ * When the scrolling region of the canvas is smaller than the canvas window,
+ * e.g.  the allocation of the canvas, it can be either centered on the window
+ * or simply made to be on the upper-left corner on the window.  This function
+ * lets you configure this property.
+ **/
+void
+ganv_canvas_base_set_center_scroll_region(GanvCanvasBase* canvas, gboolean center_scroll_region)
+{
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	canvas->center_scroll_region = center_scroll_region != 0;
+
+	scroll_to(canvas,
+	          canvas->layout.hadjustment->value,
+	          canvas->layout.vadjustment->value);
+}
+
+/**
+ * ganv_canvas_base_get_center_scroll_region:
+ * @canvas: A canvas.
+ *
+ * Returns whether the canvas is set to center the scrolling region in the window
+ * if the former is smaller than the canvas' allocation.
+ *
+ * Return value: Whether the scroll region is being centered in the canvas window.
+ **/
+gboolean
+ganv_canvas_base_get_center_scroll_region(GanvCanvasBase* canvas)
+{
+	g_return_val_if_fail(GANV_IS_CANVAS_BASE(canvas), FALSE);
+
+	return canvas->center_scroll_region ? TRUE : FALSE;
+}
+
+/**
+ * ganv_canvas_base_set_pixels_per_unit:
+ * @canvas: A canvas.
+ * @n: The number of pixels that correspond to one canvas unit.
+ *
+ * Sets the zooming factor of a canvas by specifying the number of pixels that
+ * correspond to one canvas unit.
+ *
+ * The anchor point for zooming, i.e. the point that stays fixed and all others
+ * zoom inwards or outwards from it, depends on whether the canvas is set to
+ * center the scrolling region or not.  You can control this using the
+ * ganv_canvas_base_set_center_scroll_region() function.  If the canvas is set to
+ * center the scroll region, then the center of the canvas window is used as the
+ * anchor point for zooming.  Otherwise, the upper-left corner of the canvas
+ * window is used as the anchor point.
+ **/
+void
+ganv_canvas_base_set_pixels_per_unit(GanvCanvasBase* canvas, double n)
+{
+	double ax, ay;
+	int    x1, y1;
+	int    anchor_x, anchor_y;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+	g_return_if_fail(n > GANV_CANVAS_BASE_EPSILON);
+
+	if (canvas->center_scroll_region) {
+		anchor_x = GTK_WIDGET(canvas)->allocation.width / 2;
+		anchor_y = GTK_WIDGET(canvas)->allocation.height / 2;
+	} else {
+		anchor_x = anchor_y = 0;
+	}
+
+	/* Find the coordinates of the anchor point in units. */
+	if (canvas->layout.hadjustment) {
+		ax
+		    = (canvas->layout.hadjustment->value
+		       + anchor_x) / canvas->pixels_per_unit + canvas->scroll_x1 + canvas->zoom_xofs;
+	} else {
+		ax = (0.0 + anchor_x) / canvas->pixels_per_unit + canvas->scroll_x1 + canvas->zoom_xofs;
+	}
+	if (canvas->layout.hadjustment) {
+		ay
+		    = (canvas->layout.vadjustment->value
+		       + anchor_y) / canvas->pixels_per_unit + canvas->scroll_y1 + canvas->zoom_yofs;
+	} else {
+		ay = (0.0 + anchor_y) / canvas->pixels_per_unit + canvas->scroll_y1 + canvas->zoom_yofs;
+	}
+
+	/* Now calculate the new offset of the upper left corner. */
+	x1 = ((ax - canvas->scroll_x1) * n) - anchor_x;
+	y1 = ((ay - canvas->scroll_y1) * n) - anchor_y;
+
+	canvas->pixels_per_unit = n;
+
+	scroll_to(canvas, x1, y1);
+
+	if (!(canvas->root->object.flags & GANV_ITEM_NEED_AFFINE)) {
+		canvas->root->object.flags |= GANV_ITEM_NEED_AFFINE;
+		ganv_canvas_base_request_update(canvas);
+	}
+
+	canvas->need_repick = TRUE;
+}
+
+/**
+ * ganv_canvas_base_scroll_to:
+ * @canvas: A canvas.
+ * @cx: Horizontal scrolling offset in canvas pixel units.
+ * @cy: Vertical scrolling offset in canvas pixel units.
+ *
+ * Makes a canvas scroll to the specified offsets, given in canvas pixel units.
+ * The canvas will adjust the view so that it is not outside the scrolling
+ * region.  This function is typically not used, as it is better to hook
+ * scrollbars to the canvas layout's scrolling adjusments.
+ **/
+void
+ganv_canvas_base_scroll_to(GanvCanvasBase* canvas, int cx, int cy)
+{
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	scroll_to(canvas, cx, cy);
+}
+
+/**
+ * ganv_canvas_base_get_scroll_offsets:
+ * @canvas: A canvas.
+ * @cx: Horizontal scrolling offset (return value).
+ * @cy: Vertical scrolling offset (return value).
+ *
+ * Queries the scrolling offsets of a canvas.  The values are returned in canvas
+ * pixel units.
+ **/
+void
+ganv_canvas_base_get_scroll_offsets(GanvCanvasBase* canvas, int* cx, int* cy)
+{
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	if (cx) {
+		*cx = canvas->layout.hadjustment->value;
+	}
+
+	if (cy) {
+		*cy = canvas->layout.vadjustment->value;
+	}
+}
+
+/**
+ * ganv_canvas_base_update_now:
+ * @canvas: A canvas.
+ *
+ * Forces an immediate update and redraw of a canvas.  If the canvas does not
+ * have any pending update or redraw requests, then no action is taken.  This is
+ * typically only used by applications that need explicit control of when the
+ * display is updated, like games.  It is not needed by normal applications.
+ */
+void
+ganv_canvas_base_update_now(GanvCanvasBase* canvas)
+{
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	if (!(canvas->need_update || canvas->need_redraw)) {
+		g_assert(canvas->idle_id == 0);
+		g_assert(canvas->redraw_area == NULL);
+		return;
+	}
+
+	remove_idle(canvas);
+	do_update(canvas);
+}
+
+/**
+ * ganv_canvas_base_get_item_at:
+ * @canvas: A canvas.
+ * @x: X position in world coordinates.
+ * @y: Y position in world coordinates.
+ *
+ * Looks for the item that is under the specified position, which must be
+ * specified in world coordinates.
+ *
+ * Return value: The sought item, or NULL if no item is at the specified
+ * coordinates.
+ **/
+GanvItem*
+ganv_canvas_base_get_item_at(GanvCanvasBase* canvas, double x, double y)
+{
+	GanvItem* item;
+	double    dist;
+	int       cx, cy;
+
+	g_return_val_if_fail(GANV_IS_CANVAS_BASE(canvas), NULL);
+
+	ganv_canvas_base_w2c(canvas, x, y, &cx, &cy);
+
+	dist = ganv_item_invoke_point(canvas->root, x, y, cx, cy, &item);
+	if ((int)(dist * canvas->pixels_per_unit + 0.5) <= canvas->close_enough) {
+		return item;
+	} else {
+		return NULL;
+	}
+}
+
+/* Queues an update of the canvas */
+static void
+ganv_canvas_base_request_update(GanvCanvasBase* canvas)
+{
+	GANV_CANVAS_BASE_GET_CLASS(canvas)->request_update(canvas);
+}
+
+static void
+ganv_canvas_base_request_update_real(GanvCanvasBase* canvas)
+{
+	if (canvas->need_update) {
+		return;
+	}
+
+	canvas->need_update = TRUE;
+	if (GTK_WIDGET_MAPPED((GtkWidget*)canvas)) {
+		add_idle(canvas);
+	}
+}
+
+/* Computes the union of two microtile arrays while clipping the result to the
+ * specified rectangle.  Any of the specified utas can be NULL, in which case it
+ * is taken to be an empty region.
+ */
+static ArtUta*
+uta_union_clip(ArtUta* uta1, ArtUta* uta2, ArtIRect* clip)
+{
+	ArtUta*     uta;
+	ArtUtaBbox* utiles;
+	int         clip_x1, clip_y1, clip_x2, clip_y2;
+	int         union_x1, union_y1, union_x2, union_y2;
+	int         new_x1, new_y1, new_x2, new_y2;
+	int         x, y;
+	int         ofs, ofs1, ofs2;
+
+	g_assert(clip != NULL);
+
+	/* Compute the tile indices for the clipping rectangle */
+
+	clip_x1 = clip->x0 >> ART_UTILE_SHIFT;
+	clip_y1 = clip->y0 >> ART_UTILE_SHIFT;
+	clip_x2 = (clip->x1 >> ART_UTILE_SHIFT) + 1;
+	clip_y2 = (clip->y1 >> ART_UTILE_SHIFT) + 1;
+
+	/* Get the union of the bounds of both utas */
+
+	if (!uta1) {
+		if (!uta2) {
+			return art_uta_new(clip_x1, clip_y1, clip_x1 + 1, clip_y1 + 1);
+		}
+
+		union_x1 = uta2->x0;
+		union_y1 = uta2->y0;
+		union_x2 = uta2->x0 + uta2->width;
+		union_y2 = uta2->y0 + uta2->height;
+	} else {
+		if (!uta2) {
+			union_x1 = uta1->x0;
+			union_y1 = uta1->y0;
+			union_x2 = uta1->x0 + uta1->width;
+			union_y2 = uta1->y0 + uta1->height;
+		} else {
+			union_x1 = MIN(uta1->x0, uta2->x0);
+			union_y1 = MIN(uta1->y0, uta2->y0);
+			union_x2 = MAX(uta1->x0 + uta1->width, uta2->x0 + uta2->width);
+			union_y2 = MAX(uta1->y0 + uta1->height, uta2->y0 + uta2->height);
+		}
+	}
+
+	/* Clip the union of the bounds */
+
+	new_x1 = MAX(clip_x1, union_x1);
+	new_y1 = MAX(clip_y1, union_y1);
+	new_x2 = MIN(clip_x2, union_x2);
+	new_y2 = MIN(clip_y2, union_y2);
+
+	if (( new_x1 >= new_x2) || ( new_y1 >= new_y2) ) {
+		return art_uta_new(clip_x1, clip_y1, clip_x1 + 1, clip_y1 + 1);
+	}
+
+	/* Make the new clipped union */
+
+	uta         = art_new(ArtUta, 1);
+	uta->x0     = new_x1;
+	uta->y0     = new_y1;
+	uta->width  = new_x2 - new_x1;
+	uta->height = new_y2 - new_y1;
+	uta->utiles = utiles = art_new(ArtUtaBbox, uta->width * uta->height);
+
+	ofs  = 0;
+	ofs1 = ofs2 = 0;
+
+	for (y = new_y1; y < new_y2; y++) {
+		if (uta1) {
+			ofs1 = (y - uta1->y0) * uta1->width + new_x1 - uta1->x0;
+		}
+
+		if (uta2) {
+			ofs2 = (y - uta2->y0) * uta2->width + new_x1 - uta2->x0;
+		}
+
+		for (x = new_x1; x < new_x2; x++) {
+			ArtUtaBbox bb1, bb2, bb;
+
+			if (!uta1
+			    || ( x < uta1->x0) || ( y < uta1->y0)
+			    || ( x >= uta1->x0 + uta1->width) || ( y >= uta1->y0 + uta1->height) ) {
+				bb1 = 0;
+			} else {
+				bb1 = uta1->utiles[ofs1];
+			}
+
+			if (!uta2
+			    || ( x < uta2->x0) || ( y < uta2->y0)
+			    || ( x >= uta2->x0 + uta2->width) || ( y >= uta2->y0 + uta2->height) ) {
+				bb2 = 0;
+			} else {
+				bb2 = uta2->utiles[ofs2];
+			}
+
+			if (bb1 == 0) {
+				bb = bb2;
+			} else if (bb2 == 0) {
+				bb = bb1;
+			} else {
+				bb = ART_UTA_BBOX_CONS(MIN(ART_UTA_BBOX_X0(bb1),
+				                           ART_UTA_BBOX_X0(bb2)),
+				                       MIN(ART_UTA_BBOX_Y0(bb1),
+				                           ART_UTA_BBOX_Y0(bb2)),
+				                       MAX(ART_UTA_BBOX_X1(bb1),
+				                           ART_UTA_BBOX_X1(bb2)),
+				                       MAX(ART_UTA_BBOX_Y1(bb1),
+				                           ART_UTA_BBOX_Y1(bb2)));
+			}
+
+			utiles[ofs] = bb;
+
+			ofs++;
+			ofs1++;
+			ofs2++;
+		}
+	}
+
+	return uta;
+}
+
+static inline void
+get_visible_region(GanvCanvasBase* canvas, ArtIRect* visible)
+{
+	visible->x0 = canvas->layout.hadjustment->value - canvas->zoom_xofs;
+	visible->y0 = canvas->layout.vadjustment->value - canvas->zoom_yofs;
+	visible->x1 = visible->x0 + GTK_WIDGET(canvas)->allocation.width;
+	visible->y1 = visible->y0 + GTK_WIDGET(canvas)->allocation.height;
+}
+
+/**
+ * ganv_canvas_base_request_redraw_uta:
+ * @canvas: A canvas.
+ * @uta: Microtile array that specifies the area to be redrawn.  It will
+ * be freed by this function, so the argument you pass will be invalid
+ * after you call this function.
+ *
+ * Informs a canvas that the specified area, given as a microtile array, needs
+ * to be repainted.  To be used only by item implementations.
+ **/
+void
+ganv_canvas_base_request_redraw_uta(GanvCanvasBase* canvas,
+                                    ArtUta*         uta)
+{
+	ArtIRect visible;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+	g_return_if_fail(uta != NULL);
+
+	if (!GTK_WIDGET_DRAWABLE(canvas)) {
+		art_uta_free(uta);
+		return;
+	}
+
+	get_visible_region(canvas, &visible);
+
+	if (canvas->need_redraw) {
+		ArtUta* new_uta;
+
+		g_assert(canvas->redraw_area != NULL);
+		/* ALEX: This can fail if e.g. redraw_uta is called by an item
+		   update function and we're called from update_now -> do_update
+		   because update_now sets idle_id == 0. There is also some way
+		   to get it from the expose handler (see bug #102811).
+		   g_assert (canvas->idle_id != 0);  */
+
+		new_uta = uta_union_clip(canvas->redraw_area, uta, &visible);
+		art_uta_free(canvas->redraw_area);
+		art_uta_free(uta);
+		canvas->redraw_area = new_uta;
+		if (canvas->idle_id == 0) {
+			add_idle(canvas);
+		}
+	} else {
+		ArtUta* new_uta;
+
+		g_assert(canvas->redraw_area == NULL);
+
+		new_uta = uta_union_clip(uta, NULL, &visible);
+		art_uta_free(uta);
+		canvas->redraw_area = new_uta;
+
+		canvas->need_redraw = TRUE;
+		add_idle(canvas);
+	}
+}
+
+/**
+ * ganv_canvas_base_request_redraw:
+ * @canvas: A canvas.
+ * @x1: Leftmost coordinate of the rectangle to be redrawn.
+ * @y1: Upper coordinate of the rectangle to be redrawn.
+ * @x2: Rightmost coordinate of the rectangle to be redrawn, plus 1.
+ * @y2: Lower coordinate of the rectangle to be redrawn, plus 1.
+ *
+ * Convenience function that informs a canvas that the specified rectangle needs
+ * to be repainted.  This function converts the rectangle to a microtile array
+ * and feeds it to ganv_canvas_base_request_redraw_uta().  The rectangle includes
+ * @x1 and @y1, but not @x2 and @y2.  To be used only by item implementations.
+ **/
+void
+ganv_canvas_base_request_redraw(GanvCanvasBase* canvas, int x1, int y1, int x2, int y2)
+{
+	ArtUta*  uta;
+	ArtIRect bbox;
+	ArtIRect visible;
+	ArtIRect clip;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	if (!GTK_WIDGET_DRAWABLE(canvas) || (x1 >= x2) || (y1 >= y2)) {
+		return;
+	}
+
+	bbox.x0 = x1;
+	bbox.y0 = y1;
+	bbox.x1 = x2;
+	bbox.y1 = y2;
+
+	get_visible_region(canvas, &visible);
+
+	art_irect_intersect(&clip, &bbox, &visible);
+
+	if (!art_irect_empty(&clip)) {
+		uta = art_uta_from_irect(&clip);
+		ganv_canvas_base_request_redraw_uta(canvas, uta);
+	}
+}
+
+/**
+ * ganv_canvas_base_w2c_affine:
+ * @canvas: A canvas.
+ * @affine: An affine transformation matrix (return value).
+ *
+ * Gets the affine transform that converts from world coordinates to canvas
+ * pixel coordinates.
+ **/
+void
+ganv_canvas_base_w2c_affine(GanvCanvasBase* canvas, double affine[6])
+{
+	double zooom;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+	g_return_if_fail(affine != NULL);
+
+	zooom = canvas->pixels_per_unit;
+
+	affine[0] = zooom;
+	affine[1] = 0;
+	affine[2] = 0;
+	affine[3] = zooom;
+	affine[4] = -canvas->scroll_x1 * zooom;
+	affine[5] = -canvas->scroll_y1 * zooom;
+}
+
+/**
+ * ganv_canvas_base_w2c:
+ * @canvas: A canvas.
+ * @wx: World X coordinate.
+ * @wy: World Y coordinate.
+ * @cx: X pixel coordinate (return value).
+ * @cy: Y pixel coordinate (return value).
+ *
+ * Converts world coordinates into canvas pixel coordinates.
+ **/
+void
+ganv_canvas_base_w2c(GanvCanvasBase* canvas, double wx, double wy, int* cx, int* cy)
+{
+	double   affine[6];
+	ArtPoint w, c;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	ganv_canvas_base_w2c_affine(canvas, affine);
+	w.x = wx;
+	w.y = wy;
+	art_affine_point(&c, &w, affine);
+	if (cx) {
+		*cx = floor(c.x + 0.5);
+	}
+	if (cy) {
+		*cy = floor(c.y + 0.5);
+	}
+}
+
+/**
+ * ganv_canvas_base_w2c_d:
+ * @canvas: A canvas.
+ * @wx: World X coordinate.
+ * @wy: World Y coordinate.
+ * @cx: X pixel coordinate (return value).
+ * @cy: Y pixel coordinate (return value).
+ *
+ * Converts world coordinates into canvas pixel coordinates.  This
+ * version returns coordinates in floating point coordinates, for
+ * greater precision.
+ **/
+void
+ganv_canvas_base_w2c_d(GanvCanvasBase* canvas, double wx, double wy, double* cx, double* cy)
+{
+	double   affine[6];
+	ArtPoint w, c;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	ganv_canvas_base_w2c_affine(canvas, affine);
+	w.x = wx;
+	w.y = wy;
+	art_affine_point(&c, &w, affine);
+	if (cx) {
+		*cx = c.x;
+	}
+	if (cy) {
+		*cy = c.y;
+	}
+}
+
+/**
+ * ganv_canvas_base_c2w:
+ * @canvas: A canvas.
+ * @cx: Canvas pixel X coordinate.
+ * @cy: Canvas pixel Y coordinate.
+ * @wx: X world coordinate (return value).
+ * @wy: Y world coordinate (return value).
+ *
+ * Converts canvas pixel coordinates to world coordinates.
+ **/
+void
+ganv_canvas_base_c2w(GanvCanvasBase* canvas, int cx, int cy, double* wx, double* wy)
+{
+	double   affine[6], inv[6];
+	ArtPoint w, c;
+
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	ganv_canvas_base_w2c_affine(canvas, affine);
+	art_affine_invert(inv, affine);
+	c.x = cx;
+	c.y = cy;
+	art_affine_point(&w, &c, inv);
+	if (wx) {
+		*wx = w.x;
+	}
+	if (wy) {
+		*wy = w.y;
+	}
+}
+
+/**
+ * ganv_canvas_base_window_to_world:
+ * @canvas: A canvas.
+ * @winx: Window-relative X coordinate.
+ * @winy: Window-relative Y coordinate.
+ * @worldx: X world coordinate (return value).
+ * @worldy: Y world coordinate (return value).
+ *
+ * Converts window-relative coordinates into world coordinates.  You can use
+ * this when you need to convert mouse coordinates into world coordinates, for
+ * example.
+ **/
+void
+ganv_canvas_base_window_to_world(GanvCanvasBase* canvas, double winx, double winy,
+                                 double* worldx, double* worldy)
+{
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	if (worldx) {
+		*worldx = canvas->scroll_x1 + ((winx - canvas->zoom_xofs)
+		                               / canvas->pixels_per_unit);
+	}
+
+	if (worldy) {
+		*worldy = canvas->scroll_y1 + ((winy - canvas->zoom_yofs)
+		                               / canvas->pixels_per_unit);
+	}
+}
+
+/**
+ * ganv_canvas_base_world_to_window:
+ * @canvas: A canvas.
+ * @worldx: World X coordinate.
+ * @worldy: World Y coordinate.
+ * @winx: X window-relative coordinate.
+ * @winy: Y window-relative coordinate.
+ *
+ * Converts world coordinates into window-relative coordinates.
+ **/
+void
+ganv_canvas_base_world_to_window(GanvCanvasBase* canvas, double worldx, double worldy,
+                                 double* winx, double* winy)
+{
+	g_return_if_fail(GANV_IS_CANVAS_BASE(canvas));
+
+	if (winx) {
+		*winx = (canvas->pixels_per_unit) * (worldx - canvas->scroll_x1) + canvas->zoom_xofs;
+	}
+
+	if (winy) {
+		*winy = (canvas->pixels_per_unit) * (worldy - canvas->scroll_y1) + canvas->zoom_yofs;
+	}
+}
+
+static gboolean
+boolean_handled_accumulator(GSignalInvocationHint* ihint,
+                            GValue*                return_accu,
+                            const GValue*          handler_return,
+                            gpointer               dummy)
+{
+	gboolean continue_emission;
+	gboolean signal_handled;
+
+	signal_handled = g_value_get_boolean(handler_return);
+	g_value_set_boolean(return_accu, signal_handled);
+	continue_emission = !signal_handled;
+
+	return continue_emission;
+}
+
+/* Class initialization function for GanvItemClass */
+static void
+ganv_item_class_init(GanvItemClass* class)
+{
+	GObjectClass* gobject_class;
+
+	gobject_class = (GObjectClass*)class;
+
+	item_parent_class = g_type_class_peek_parent(class);
+
+	gobject_class->set_property = ganv_item_set_property;
+	gobject_class->get_property = ganv_item_get_property;
+
+	g_object_class_install_property
+	    (gobject_class, ITEM_PROP_PARENT,
+	    g_param_spec_object("parent", NULL, NULL,
+	                        GANV_TYPE_ITEM,
+	                        (G_PARAM_READABLE | G_PARAM_WRITABLE)));
+
+	item_signals[ITEM_EVENT]
+	    = g_signal_new("event",
+	                   G_TYPE_FROM_CLASS(class),
+	                   G_SIGNAL_RUN_LAST,
+	                   G_STRUCT_OFFSET(GanvItemClass, event),
+	                   boolean_handled_accumulator, NULL,
+	                   ganv_marshal_BOOLEAN__BOXED,
+	                   G_TYPE_BOOLEAN, 1,
+	                   GDK_TYPE_EVENT | G_SIGNAL_TYPE_STATIC_SCOPE);
+
+	gobject_class->dispose = ganv_item_dispose;
+
+	class->realize   = ganv_item_realize;
+	class->unrealize = ganv_item_unrealize;
+	class->map       = ganv_item_map;
+	class->unmap     = ganv_item_unmap;
+	class->update    = ganv_item_update;
+}