X11: Use ephemeral Cairo surfaces for drawing

This uses a similar approach to Gtk, where surfaces are created every draw
call.  It is a bit slower for a single application in most cases, but uses less
memory when drawing isn't happening and plays more nicely with other views or
applications.

1 files changed, 66 insertions, 51 deletions

diff --git a/pugl/detail/x11_cairo.c b/pugl/detail/x11_cairo.c
index 7a02dcd..03a3f8e 100644
--- a/pugl/detail/x11_cairo.c
+++ b/pugl/detail/x11_cairo.c
@@ -22,6 +22,7 @@
 #include "pugl/detail/x11.h"
 #include "pugl/pugl.h"
 #include "pugl/pugl_cairo.h"
+#include "pugl/pugl_stub.h"
 
 #include <X11/Xutil.h>
 #include <cairo-xlib.h>
@@ -31,36 +32,56 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-typedef struct  {
+typedef struct {
 	cairo_surface_t* back;
 	cairo_surface_t* front;
 	cairo_t*         cr;
 } PuglX11CairoSurface;
 
+static void
+puglX11CairoClose(PuglView* view)
+{
+	PuglInternals* const       impl    = view->impl;
+	PuglX11CairoSurface* const surface = (PuglX11CairoSurface*)impl->surface;
+
+	cairo_surface_destroy(surface->front);
+	cairo_surface_destroy(surface->back);
+	surface->front = surface->back = NULL;
+}
+
 static PuglStatus
-puglX11CairoCreate(PuglView* view)
+puglX11CairoOpen(PuglView* view)
 {
-	PuglInternals* const impl    = view->impl;
-	const int            width   = (int)view->frame.width;
-	const int            height  = (int)view->frame.height;
-	PuglX11CairoSurface  surface = { 0 };
-
-	surface.back = cairo_xlib_surface_create(
-		impl->display, impl->win, impl->vi->visual, width, height);
-	surface.front = cairo_surface_create_similar(
-		surface.back, CAIRO_CONTENT_COLOR, width, height);
-
-	cairo_status_t st = CAIRO_STATUS_SUCCESS;
-	if (!surface.back || !surface.front ||
-	    (st = cairo_surface_status(surface.back)) ||
-	    (st = cairo_surface_status(surface.front))) {
-		cairo_surface_destroy(surface.front);
-		cairo_surface_destroy(surface.back);
+	PuglInternals* const       impl    = view->impl;
+	PuglX11CairoSurface* const surface = (PuglX11CairoSurface*)impl->surface;
+
+	surface->back = cairo_xlib_surface_create(impl->display,
+	                                          impl->win,
+	                                          impl->vi->visual,
+	                                          (int)view->frame.width,
+	                                          (int)view->frame.height);
+
+	surface->front = cairo_surface_create_similar(
+	        surface->back,
+	        cairo_surface_get_content(surface->back),
+	        (int)view->frame.width,
+	        (int)view->frame.height);
+
+	if (cairo_surface_status(surface->back) ||
+	    cairo_surface_status(surface->front)) {
+		puglX11CairoClose(view);
 		return PUGL_CREATE_CONTEXT_FAILED;
 	}
 
-	impl->surface = calloc(1, sizeof(PuglX11CairoSurface));
-	*(PuglX11CairoSurface*)impl->surface = surface;
+	return PUGL_SUCCESS;
+}
+
+static PuglStatus
+puglX11CairoCreate(PuglView* view)
+{
+	PuglInternals* const impl = view->impl;
+
+	impl->surface = (cairo_surface_t*)calloc(1, sizeof(PuglX11CairoSurface));
 
 	return PUGL_SUCCESS;
 }
@@ -71,10 +92,9 @@ puglX11CairoDestroy(PuglView* view)
 	PuglInternals* const       impl    = view->impl;
 	PuglX11CairoSurface* const surface = (PuglX11CairoSurface*)impl->surface;
 
-	cairo_surface_destroy(surface->front);
-	cairo_surface_destroy(surface->back);
+	puglX11CairoClose(view);
 	free(surface);
-	impl->surface = NULL;
+
 	return PUGL_SUCCESS;
 }
 
@@ -83,15 +103,17 @@ puglX11CairoEnter(PuglView* view, const PuglEventExpose* expose)
 {
 	PuglInternals* const       impl    = view->impl;
 	PuglX11CairoSurface* const surface = (PuglX11CairoSurface*)impl->surface;
+	PuglStatus                 st      = PUGL_SUCCESS;
 
-	if (expose) {
+	if (expose && !(st = puglX11CairoOpen(view))) {
 		surface->cr = cairo_create(surface->front);
-		if (!surface->cr || cairo_status(surface->cr)) {
-			return PUGL_CREATE_CONTEXT_FAILED;
+
+		if (cairo_status(surface->cr)) {
+			st = PUGL_CREATE_CONTEXT_FAILED;
 		}
 	}
 
-	return PUGL_SUCCESS;
+	return st;
 }
 
 static PuglStatus
@@ -101,35 +123,28 @@ puglX11CairoLeave(PuglView* view, const PuglEventExpose* expose)
 	PuglX11CairoSurface* const surface = (PuglX11CairoSurface*)impl->surface;
 
 	if (expose) {
-		// Destroy front context that was used by the user for drawing
+		// Destroy front context and create a new one for drawing to the back
 		cairo_destroy(surface->cr);
-
-		// Create a new context for the back and paint the front onto it
 		surface->cr = cairo_create(surface->back);
+
+		// Clip to expose region
+		cairo_rectangle(surface->cr,
+		                expose->x,
+		                expose->y,
+		                expose->width,
+		                expose->height);
+		cairo_clip(surface->cr);
+
+		// Paint front onto back
 		cairo_set_source_surface(surface->cr, surface->front, 0, 0);
+		cairo_set_operator(surface->cr, CAIRO_OPERATOR_SOURCE);
 		cairo_paint(surface->cr);
-		cairo_destroy(surface->cr);
-		surface->cr = NULL;
 
-		// Flush back to X
+		// Flush to X and close everything
+		cairo_destroy(surface->cr);
 		cairo_surface_flush(surface->back);
-	}
-
-	return PUGL_SUCCESS;
-}
-
-static PuglStatus
-puglX11CairoResize(PuglView* view, int width, int height)
-{
-	PuglInternals* const       impl    = view->impl;
-	PuglX11CairoSurface* const surface = (PuglX11CairoSurface*)impl->surface;
-
-	cairo_xlib_surface_set_size(surface->back, width, height);
-
-	cairo_surface_destroy(surface->front);
-	if (!(surface->front = cairo_surface_create_similar(
-		      surface->back, CAIRO_CONTENT_COLOR, width, height))) {
-		return PUGL_CREATE_CONTEXT_FAILED;
+		puglX11CairoClose(view);
+		surface->cr = NULL;
 	}
 
 	return PUGL_SUCCESS;
@@ -153,7 +168,7 @@ puglCairoBackend(void)
 		puglX11CairoDestroy,
 		puglX11CairoEnter,
 		puglX11CairoLeave,
-		puglX11CairoResize,
+		puglStubResize,
 		puglX11CairoGetContext
 	};