Move group implementation to separate files.

git-svn-id: http://svn.drobilla.net/lad/trunk/ganv@3870 a436a847-0d15-0410-975c-d299462d15a1

4 files changed, 540 insertions, 600 deletions

diff --git a/src/Canvas.cpp b/src/Canvas.cpp
index db02ffe..4f081fa 100644
--- a/src/Canvas.cpp
+++ b/src/Canvas.cpp
@@ -166,7 +166,7 @@ struct GanvCanvasImpl {
 		return ((GanvCanvasImpl*)impl)->on_event(ev);
 	}
 
-	GanvGroup* root() {
+	GanvItem* root() {
 		return ganv_canvas_base_root(GANV_CANVAS_BASE(_gcanvas));
 	}
 
@@ -1670,7 +1670,7 @@ Canvas::for_each_selected_edge(EdgePtrFunction f, void* data)
 	}
 }
 
-GanvGroup*
+GanvItem*
 Canvas::root()
 {
 	return ganv_canvas_base_root(GANV_CANVAS_BASE(impl()->_gcanvas));
@@ -1900,7 +1900,7 @@ ganv_canvas_resize(GanvCanvas* canvas, double width, double height)
 	canvas->impl->resize(width, height);
 }
 
-GanvGroup*
+GanvItem*
 ganv_canvas_get_root(const GanvCanvas* canvas)
 {
 	return ganv_canvas_base_root(GANV_CANVAS_BASE(canvas->impl->_gcanvas));
diff --git a/src/canvas-base.c b/src/canvas-base.c
index ef523f0..04cdf55 100644
--- a/src/canvas-base.c
+++ b/src/canvas-base.c
@@ -27,6 +27,7 @@
 #include <cairo.h>
 
 #include "ganv/canvas-base.h"
+#include "ganv/group.h"
 
 #include "./gettext.h"
 #include "./ganv-marshal.h"
@@ -35,21 +36,12 @@
 #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])
+                         | GANV_CANVAS_BASE_UPDATE_VISIBILITY)
 
 enum {
 	ITEM_PROP_0,
@@ -120,10 +112,16 @@ ganv_item_new(GanvItem* parent, GType type, const gchar* first_arg_name, ...)
 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;
+	GanvItemClass* parent_class = GANV_ITEM_GET_CLASS(item->parent);
+	if (parent_class->add) {
+		parent_class->add(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;
+	} else {
+		g_error("item added to non-parent item\n");
+	}
 }
 
 /* Set_property handler for canvas items */
@@ -255,7 +253,7 @@ ganv_item_dispose(GObject* object)
 	}
 
 	if (item->parent) {
-		group_remove(GANV_GROUP(item->parent), item);
+		GANV_ITEM_GET_CLASS(item->parent)->remove(item->parent, item);
 	}
 
 	G_OBJECT_CLASS(item_parent_class)->dispose(object);
@@ -299,12 +297,22 @@ static void
 ganv_item_update(GanvItem* item, int flags)
 {
 	GTK_OBJECT_UNSET_FLAGS(item, GANV_ITEM_NEED_UPDATE);
-	GTK_OBJECT_UNSET_FLAGS(item, GANV_ITEM_NEED_CLIP);
 	GTK_OBJECT_UNSET_FLAGS(item, GANV_ITEM_NEED_VIS);
 }
 
-/*
- * This routine invokes the update method of the item
+/* Point handler for canvas items */
+static double
+ganv_item_point(GanvItem* item,
+                double x, double y,
+                int cx, int cy,
+                GanvItem** actual_item)
+{
+	*actual_item = NULL;
+	return G_MAXDOUBLE;
+}
+
+/**
+ * Invoke 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
@@ -313,16 +321,11 @@ ganv_item_update(GanvItem* item, int flags)
  * 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
+void
 ganv_item_invoke_update(GanvItem* item, int flags)
 {
 	int child_flags = flags;
-	if (!(item->object.flags & GANV_ITEM_VISIBLE)) {
-		child_flags &= ~GANV_CANVAS_BASE_UPDATE_IS_VISIBLE;
-	}
 
 	/* apply object flags to child flags */
 
@@ -332,10 +335,6 @@ ganv_item_invoke_update(GanvItem* item, int flags)
 		child_flags |= GANV_CANVAS_BASE_UPDATE_REQUESTED;
 	}
 
-	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;
 	}
@@ -348,25 +347,6 @@ ganv_item_invoke_update(GanvItem* item, int flags)
 }
 
 /**
- * Invoke the point method of the item.
- * The arguments x, y should be in the parent item local coordinates.
- */
-static double
-ganv_item_invoke_point(GanvItem* item, double x, double y, int cx, int cy,
-                       GanvItem** actual_item)
-{
-	// Transform x and y to item local coordinates
-	x -= item->x;
-	y -= item->y;
-
-	if (GANV_ITEM_GET_CLASS(item)->point) {
-		return GANV_ITEM_GET_CLASS(item)->point(item, x, y, cx, cy, actual_item);
-	}
-
-	return G_MAXDOUBLE;
-}
-
-/**
  * ganv_item_set:
  * @item: A canvas item.
  * @first_arg_name: The list of object argument name/value pairs used to configure the item.
@@ -751,47 +731,6 @@ is_descendant(GanvItem* item, GanvItem* parent)
 }
 
 /**
- * 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.
  *
@@ -909,510 +848,6 @@ ganv_item_request_update(GanvItem* item)
 	}
 }
 
-/*** 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, 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, cairo_t* cr,
-                            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
-}
-
-/* Set_property handler for canvas groups */
-static void
-ganv_group_set_property(GObject* gobject, guint param_id,
-                        const GValue* value, GParamSpec* pspec)
-{
-	g_return_if_fail(GANV_IS_GROUP(gobject));
-
-	GanvItem* item = GANV_ITEM(gobject);
-
-	switch (param_id) {
-	case GROUP_PROP_X:
-		item->x = g_value_get_double(value);
-		ganv_item_request_update(item);
-		break;
-
-	case GROUP_PROP_Y:
-		item->y = g_value_get_double(value);
-		ganv_item_request_update(item);
-		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:
-		g_value_set_double(value, item->x);
-		break;
-
-	case GROUP_PROP_Y:
-		g_value_set_double(value, item->y);
-		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, int flags)
-{
-	GanvGroup* group;
-	GList*     list;
-	GanvItem*  i;
-
-	group = GANV_GROUP(item);
-
-	(*group_parent_class->update)(item, flags);
-
-	double min_x = 0.0;
-	double min_y = 0.0;
-	double max_x = 0.0;
-	double max_y = 0.0;
-
-	for (list = group->item_list; list; list = list->next) {
-		i = list->data;
-
-		ganv_item_invoke_update(i, flags);
-
-		min_x = fmin(min_x, fmin(i->x1, i->x2));
-		min_y = fmin(min_y, fmin(i->y1, i->y2));
-		max_x = fmax(max_x, fmax(i->x1, i->x2));
-		max_y = fmax(max_y, fmax(i->y2, i->y2));
-	}
-	item->x1 = min_x;
-	item->y1 = min_y;
-	item->x2 = max_x;
-	item->y2 = max_y;
-}
-
-/* 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, cairo_t* cr,
-                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, cr, 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 ***/
 
@@ -2149,8 +1584,11 @@ pick_current_item(GanvCanvasBase* canvas, GdkEvent* event)
 		/* 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);
+			GANV_ITEM_GET_CLASS(canvas->root)->point(
+				canvas->root,
+				x - canvas->root->x, y - canvas->root->y,
+				cx, cy,
+				&canvas->new_current_item);
 		} else {
 			canvas->new_current_item = NULL;
 		}
@@ -2640,12 +2078,12 @@ add_idle(GanvCanvasBase* canvas)
  *
  * Return value: The root group of the specified canvas.
  **/
-GanvGroup*
+GanvItem*
 ganv_canvas_base_root(GanvCanvasBase* canvas)
 {
 	g_return_val_if_fail(GANV_IS_CANVAS_BASE(canvas), NULL);
 
-	return GANV_GROUP(canvas->root);
+	return canvas->root;
 }
 
 /**
@@ -2921,7 +2359,11 @@ ganv_canvas_base_get_item_at(GanvCanvasBase* canvas, double x, double y)
 
 	ganv_canvas_base_w2c(canvas, x, y, &cx, &cy);
 
-	dist = ganv_item_invoke_point(canvas->root, x, y, cx, cy, &item);
+	dist = GANV_ITEM_GET_CLASS(canvas->root)->point(
+		canvas->root,
+		x - canvas->root->x, y - canvas->root->y,
+		cx, cy,
+		&item);
 	if ((int)(dist * canvas->pixels_per_unit + 0.5) <= canvas->close_enough) {
 		return item;
 	} else {
@@ -3227,4 +2669,5 @@ ganv_item_class_init(GanvItemClass* class)
 	class->map       = ganv_item_map;
 	class->unmap     = ganv_item_unmap;
 	class->update    = ganv_item_update;
+	class->point     = ganv_item_point;
 }
diff --git a/src/ganv-private.h b/src/ganv-private.h
index 8e9af59..1c25716 100644
--- a/src/ganv-private.h
+++ b/src/ganv-private.h
@@ -23,6 +23,7 @@ extern "C" {
 #include <cairo.h>
 
 #include "ganv/types.h"
+#include "ganv/text.h"
 
 extern guint signal_moved;
 
@@ -198,6 +199,12 @@ ganv_canvas_port_event(GanvCanvas* canvas,
                        GanvPort*   port,
                        GdkEvent*   event);
 
+void
+ganv_item_invoke_update(GanvItem* item, int flags);
+
+void
+ganv_canvas_base_request_update(GanvCanvasBase* canvas);
+
 #ifdef __cplusplus
 }  /* extern "C" */
 #endif
diff --git a/src/group.c b/src/group.c
new file mode 100644
index 0000000..1ebb42c
--- /dev/null
+++ b/src/group.c
@@ -0,0 +1,490 @@
+/* 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 GnomeCanvasGroup, by Federico Mena <federico@nuclecu.unam.mx>
+ * and Raph Levien <raph@gimp.org>
+ * Copyright 1997-2000 Free Software Foundation
+ */
+
+#include <math.h>
+
+#include "ganv/canvas-base.h"
+#include "ganv/group.h"
+
+#include "./gettext.h"
+#include "./ganv-private.h"
+
+enum {
+	GROUP_PROP_0,
+	GROUP_PROP_X,
+	GROUP_PROP_Y
+};
+
+G_DEFINE_TYPE(GanvGroup, ganv_group, GANV_TYPE_ITEM)
+
+static GanvItemClass* group_parent_class;
+
+static void
+ganv_group_init(GanvGroup* group)
+{
+}
+
+static void
+ganv_group_set_property(GObject* gobject, guint param_id,
+                        const GValue* value, GParamSpec* pspec)
+{
+	g_return_if_fail(GANV_IS_GROUP(gobject));
+
+	GanvItem* item = GANV_ITEM(gobject);
+
+	switch (param_id) {
+	case GROUP_PROP_X:
+		item->x = g_value_get_double(value);
+		ganv_item_request_update(item);
+		break;
+
+	case GROUP_PROP_Y:
+		item->y = g_value_get_double(value);
+		ganv_item_request_update(item);
+		break;
+
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(gobject, param_id, pspec);
+		break;
+	}
+}
+
+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:
+		g_value_set_double(value, item->x);
+		break;
+
+	case GROUP_PROP_Y:
+		g_value_set_double(value, item->y);
+		break;
+
+	default:
+		G_OBJECT_WARN_INVALID_PROPERTY_ID(gobject, param_id, pspec);
+		break;
+	}
+}
+
+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);
+	}
+}
+
+static void
+ganv_group_update(GanvItem* item, int flags)
+{
+	GanvGroup* group;
+	GList*     list;
+	GanvItem*  i;
+
+	group = GANV_GROUP(item);
+
+	(*group_parent_class->update)(item, flags);
+
+	double min_x = 0.0;
+	double min_y = 0.0;
+	double max_x = 0.0;
+	double max_y = 0.0;
+
+	for (list = group->item_list; list; list = list->next) {
+		i = list->data;
+
+		ganv_item_invoke_update(i, flags);
+
+		min_x = fmin(min_x, fmin(i->x1, i->x2));
+		min_y = fmin(min_y, fmin(i->y1, i->y2));
+		max_x = fmax(max_x, fmax(i->x1, i->x2));
+		max_y = fmax(max_y, fmax(i->y2, i->y2));
+	}
+	item->x1 = min_x;
+	item->y1 = min_y;
+	item->x2 = max_x;
+	item->y2 = max_y;
+}
+
+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);
+}
+
+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);
+}
+
+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);
+}
+
+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);
+}
+
+static void
+ganv_group_draw(GanvItem* item, cairo_t* cr,
+                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, cr, x, y, width, height);
+			}
+		}
+	}
+}
+
+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_GET_CLASS(child)->point(
+				child,
+				gx - child->x, gy - child->y,
+				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;
+}
+
+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;
+}
+
+static void
+ganv_group_add(GanvItem* parent, GanvItem* item)
+{
+	GanvGroup* group = GANV_GROUP(parent);
+	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");
+}
+
+static void
+ganv_group_remove(GanvItem* parent, GanvItem* item)
+{
+	GanvGroup* group = GANV_GROUP(parent);
+	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;
+		}
+	}
+}
+
+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->add       = ganv_group_add;
+	item_class->remove    = ganv_group_remove;
+	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;
+}