[gtk-vnc] Re-introduce a server side Pixmap to cache framebuffer

[Daniel P. Berrange <dberrange src gnome org>]

commit 20a8875df00d7e6d918fa7b94aca2baebe034cb5
Author: Daniel P. Berrange <berrange redhat com>
Date:   Mon Nov 29 16:12:53 2010 +0000

    Re-introduce a server side Pixmap to cache framebuffer
    
    Despite use of clipping during drawing, rendering directly
    from the client side cairo image, to the window incurred
    a serious performance penalty for some users' X servers.
    Re-introduce a server side copy of the VNC desktop using
    a cairo surface, backed by an X Pixmap. This uses cairo
    APIs directly, avoiding any need for GdkPixmap.

 src/vncdisplay.c |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 55 insertions(+), 2 deletions(-)
---
diff --git a/src/vncdisplay.c b/src/vncdisplay.c
index 0b7e800..33d2623 100644
--- a/src/vncdisplay.c
+++ b/src/vncdisplay.c
@@ -50,6 +50,7 @@ struct _VncDisplayPrivate
 
 	VncConnection *conn;
 	VncCairoFramebuffer *fb;
+	cairo_surface_t *fbCache; /* Cache on server display */
 
 	VncDisplayDepthColor depth;
 
@@ -282,6 +283,32 @@ static GdkCursor *create_null_cursor(void)
 	return cursor;
 }
 
+
+static void setup_surface_cache(VncDisplay *dpy, cairo_t *crWin, int w, int h)
+{
+	VncDisplayPrivate *priv = dpy->priv;
+	cairo_surface_t *win = cairo_get_target(crWin);
+	cairo_t *crCache;
+
+	if (priv->fbCache)
+		return;
+
+	/* Creates a Pixmap on the X11 server matching the Window */
+	priv->fbCache = cairo_surface_create_similar(win,
+						     CAIRO_CONTENT_COLOR,
+						     w, h);
+	crCache = cairo_create(priv->fbCache);
+
+	/* Copy our local framebuffer contents to the Pixmap */
+	cairo_set_source_surface(crCache,
+				 vnc_cairo_framebuffer_get_surface(priv->fb),
+				 0,
+				 0);
+	cairo_paint(crCache);
+
+	cairo_destroy(crCache);
+}
+
 static gboolean draw_event(GtkWidget *widget, cairo_t *cr)
 {
 	VncDisplay *obj = VNC_DISPLAY(widget);
@@ -293,6 +320,8 @@ static gboolean draw_event(GtkWidget *widget, cairo_t *cr)
 	if (priv->fb) {
 		fbw = vnc_framebuffer_get_width(VNC_FRAMEBUFFER(priv->fb));
 		fbh = vnc_framebuffer_get_height(VNC_FRAMEBUFFER(priv->fb));
+
+		setup_surface_cache(obj, cr, fbw, fbh);
 	}
 
 	gdk_drawable_get_size(gtk_widget_get_window(widget), &ww, &wh);
@@ -327,12 +356,12 @@ static gboolean draw_event(GtkWidget *widget, cairo_t *cr)
 			sy = (double)wh / (double)fbh;
 			cairo_scale(cr, sx, sy);
 			cairo_set_source_surface(cr,
-						 vnc_cairo_framebuffer_get_surface(priv->fb),
+						 priv->fbCache,
 						 0,
 						 0);
 		} else {
 			cairo_set_source_surface(cr,
-						 vnc_cairo_framebuffer_get_surface(priv->fb),
+						 priv->fbCache,
 						 mx,
 						 my);
 		}
@@ -848,6 +877,22 @@ static void on_framebuffer_update(VncConnection *conn G_GNUC_UNUSED,
 
 	gdk_drawable_get_size(gtk_widget_get_window(widget), &ww, &wh);
 
+	/* If we have a pixmap, update the region which changed.
+	 * If we don't have a pixmap, the entire thing will be
+	 * created & rendered during the drawing handler
+	 */
+	if (priv->fbCache) {
+		cairo_t *cr = cairo_create(priv->fbCache);
+		cairo_surface_t *surface = vnc_cairo_framebuffer_get_surface(priv->fb);
+
+		cairo_rectangle(cr, x, y, w, h);
+		cairo_clip(cr);
+		cairo_set_source_surface(cr, surface, 0, 0);
+		cairo_paint(cr);
+
+		cairo_destroy(cr);
+	}
+
 	if (priv->allow_scaling) {
 		double sx, sy;
 
@@ -905,6 +950,10 @@ static void do_framebuffer_init(VncDisplay *obj,
 		g_object_unref(priv->fb);
 		priv->fb = NULL;
 	}
+	if (priv->fbCache) {
+		cairo_surface_destroy(priv->fbCache);
+		priv->fbCache = NULL;
+	}
 
 	if (priv->null_cursor == NULL) {
 		priv->null_cursor = create_null_cursor();
@@ -1496,6 +1545,10 @@ static void vnc_display_finalize (GObject *obj)
 		g_object_unref(priv->fb);
 		priv->fb = NULL;
 	}
+	if (priv->fbCache) {
+		cairo_surface_destroy(priv->fbCache);
+		priv->fbCache = NULL;
+	}
 
 	if (priv->null_cursor) {
 		gdk_cursor_unref (priv->null_cursor);