[gthumb: 15/129] implemented _cairo_image_surface_has_alpha

[Paolo Bacchilega <paobac src gnome org>]

commit fff270609b34250ed589cae45764058c671da0b6
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Fri Apr 15 12:09:37 2011 +0200

    implemented _cairo_image_surface_has_alpha
    
    attach the has_alpha info to the cairo surface

 gthumb/cairo-utils.c      |   55 +++++++++++++++++++++++++++++++++++++-------
 gthumb/cairo-utils.h      |    1 +
 gthumb/gth-image-viewer.c |    4 +-
 gthumb/pixbuf-utils.c     |    5 ++-
 4 files changed, 52 insertions(+), 13 deletions(-)
---
diff --git a/gthumb/cairo-utils.c b/gthumb/cairo-utils.c
index 21410e2..7a16d54 100644
--- a/gthumb/cairo-utils.c
+++ b/gthumb/cairo-utils.c
@@ -24,6 +24,22 @@
 #include "cairo-utils.h"
 
 
+typedef struct {
+	gboolean has_alpha;
+} cairo_surface_metadata_t;
+
+
+static cairo_user_data_key_t surface_metadata_key;
+
+
+static void
+surface_metadata_free (void *data)
+{
+	cairo_surface_metadata_t *metadata = data;
+	g_free (metadata);
+}
+
+
 void
 _gdk_color_to_cairo_color (GdkColor      *g_color,
 			   cairo_color_t *c_color)
@@ -113,18 +129,35 @@ _cairo_clear_surface (cairo_surface_t  **surface)
 }
 
 
+gboolean
+_cairo_image_surface_has_alpha (cairo_surface_t *surface)
+{
+	cairo_surface_metadata_t *metadata;
+
+	if (surface == NULL)
+		return FALSE;
+
+	metadata = cairo_surface_get_user_data (surface, &surface_metadata_key);
+	if (metadata != NULL)
+		return metadata->has_alpha;
+
+	return cairo_image_surface_get_format (surface) == CAIRO_FORMAT_ARGB32;
+}
+
+
 cairo_surface_t *
 _cairo_image_surface_create_from_pixbuf (GdkPixbuf *pixbuf)
 {
-	cairo_surface_t *surface;
-	int              width;
-	int              height;
-	int              p_stride;
-	int              p_n_channels;
-	guchar          *p_pixels;
-	int              s_stride;
-	unsigned char   *s_pixels;
-	int              h, w;
+	cairo_surface_t          *surface;
+	cairo_surface_metadata_t *metadata;
+	int                      width;
+	int                      height;
+	int                      p_stride;
+	int                      p_n_channels;
+	guchar                  *p_pixels;
+	int                      s_stride;
+	unsigned char           *s_pixels;
+	int                      h, w;
 
 	if (pixbuf == NULL)
 		return NULL;
@@ -140,6 +173,10 @@ _cairo_image_surface_create_from_pixbuf (GdkPixbuf *pixbuf)
 	s_stride = cairo_image_surface_get_stride (surface);
 	s_pixels = cairo_image_surface_get_data (surface);
 
+	metadata = g_new0 (cairo_surface_metadata_t, 1);
+	metadata->has_alpha = (p_n_channels == 4);
+	cairo_surface_set_user_data (surface, &surface_metadata_key, metadata, surface_metadata_free);
+
 	if (p_n_channels == 4) {
 		guchar *s_iter;
 		guchar *p_iter;
diff --git a/gthumb/cairo-utils.h b/gthumb/cairo-utils.h
index 6decc5c..ea78fbb 100644
--- a/gthumb/cairo-utils.h
+++ b/gthumb/cairo-utils.h
@@ -87,6 +87,7 @@ void         _cairo_paint_full_gradient         (cairo_surface_t   *surface,
 				 	 	 GdkColor          *v_color1,
 				 	 	 GdkColor          *v_color2);
 void         _cairo_clear_surface               (cairo_surface_t  **surface);
+gboolean     _cairo_image_surface_has_alpha     (cairo_surface_t   *surface);
 cairo_surface_t *
 	     _cairo_image_surface_create_from_pixbuf
 	     	     	     	     	        (GdkPixbuf         *pixbuf);
diff --git a/gthumb/gth-image-viewer.c b/gthumb/gth-image-viewer.c
index 739b3e8..a60d5c2 100644
--- a/gthumb/gth-image-viewer.c
+++ b/gthumb/gth-image-viewer.c
@@ -1845,7 +1845,7 @@ gth_image_viewer_get_original_size (GthImageViewer *self,
 gboolean
 gth_image_viewer_get_has_alpha (GthImageViewer *self)
 {
-	return TRUE; /* FIXME */
+	return _cairo_image_surface_has_alpha (self->priv->surface);
 }
 
 
@@ -2591,7 +2591,7 @@ gth_image_viewer_paint_background (GthImageViewer *self,
 		cairo_stroke (cr);
 	}
 
-	if (TRUE /* FIXME gth_image_viewer_get_has_alpha (self) */) {
+	if (gth_image_viewer_get_has_alpha (self)) {
 
 		/* Draw the background for the transparency */
 
diff --git a/gthumb/pixbuf-utils.c b/gthumb/pixbuf-utils.c
index 1382f55..52479c4 100644
--- a/gthumb/pixbuf-utils.c
+++ b/gthumb/pixbuf-utils.c
@@ -24,6 +24,7 @@
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include "cairo-utils.h"
 #include "pixbuf-utils.h"
 
 
@@ -65,7 +66,7 @@ _gdk_pixbuf_new_from_cairo_context (cairo_t *cr)
 }
 
 
-/* Taken from http://www.gtkforums.com/about5204.html
+/* Started from from http://www.gtkforums.com/about5204.html
  * Author: tadeboro */
 GdkPixbuf *
 _gdk_pixbuf_new_from_cairo_surface (cairo_surface_t *surface)
@@ -87,7 +88,7 @@ _gdk_pixbuf_new_from_cairo_surface (cairo_surface_t *surface)
 	s_stride = cairo_image_surface_get_stride (surface);
 	s_pixels = cairo_image_surface_get_data (surface);
 
-	pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, TRUE, 8, width, height);
+	pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, _cairo_image_surface_has_alpha (surface), 8, width, height);
 	p_stride = gdk_pixbuf_get_rowstride (pixbuf);
 	p_pixels = gdk_pixbuf_get_pixels (pixbuf);
 	p_n_channels = gdk_pixbuf_get_n_channels (pixbuf);