[gtk+/gtk-3-10] gdkcairo: Split out a function

[Matthias Clasen <matthiasc src gnome org>]

commit f1ea85e514e85d13e293466cb2df527640a4e14e
Author: Benjamin Otte <otte redhat com>
Date:   Tue Sep 24 16:34:24 2013 +0200

    gdkcairo: Split out a function
    
    This is in preparation for the next patch.

 gdk/gdkcairo.c |   94 +++++++++++++++++++++++++++++++++++---------------------
 1 files changed, 59 insertions(+), 35 deletions(-)
---
diff --git a/gdk/gdkcairo.c b/gdk/gdkcairo.c
index 5dba69a..d16a619 100644
--- a/gdk/gdkcairo.c
+++ b/gdk/gdkcairo.c
@@ -175,45 +175,32 @@ gdk_cairo_region (cairo_t              *cr,
     }
 }
 
-/**
- * gdk_cairo_surface_create_from_pixbuf:
- * @pixbuf: a #GdkPixbuf
- * @scale: the scale of the new surface, or 0 to use same as @window
- * @for_window: The window this will be drawn to, on %NULL.
- *
- * Creates an image surface with the same contents as
- * the pixbuf.
- *
- * Returns: a new cairo surface, must be freed with cairo_surface_destroy()
- *
- * Since: 3.10
- */
-cairo_surface_t *
-gdk_cairo_surface_create_from_pixbuf (const GdkPixbuf *pixbuf,
-                                      int              scale,
-                                      GdkWindow       *for_window)
+static void
+gdk_cairo_surface_paint_pixbuf (cairo_surface_t *surface,
+                                const GdkPixbuf *pixbuf)
 {
-  gint width = gdk_pixbuf_get_width (pixbuf);
-  gint height = gdk_pixbuf_get_height (pixbuf);
-  guchar *gdk_pixels = gdk_pixbuf_get_pixels (pixbuf);
-  int gdk_rowstride = gdk_pixbuf_get_rowstride (pixbuf);
-  int n_channels = gdk_pixbuf_get_n_channels (pixbuf);
-  int cairo_stride;
-  guchar *cairo_pixels;
-  cairo_format_t format;
-  cairo_surface_t *surface;
+  gint width, height;
+  guchar *gdk_pixels, *cairo_pixels;
+  int gdk_rowstride, cairo_stride;
+  int n_channels;
   int j;
 
-  if (n_channels == 3)
-    format = CAIRO_FORMAT_RGB24;
-  else
-    format = CAIRO_FORMAT_ARGB32;
+  /* This function can't just copy any pixbuf to any surface, be
+   * sure to read the invariants here before calling it */
 
-  surface =
-     gdk_window_create_similar_image_surface (for_window,
-                                             format,
-                                             width, height,
-                                             scale);
+  g_assert (cairo_surface_get_type (surface) == CAIRO_SURFACE_TYPE_IMAGE);
+  g_assert (cairo_image_surface_get_format (surface) == CAIRO_FORMAT_RGB24 ||
+            cairo_image_surface_get_format (surface) == CAIRO_FORMAT_ARGB32);
+  g_assert (cairo_image_surface_get_width (surface) == gdk_pixbuf_get_width (pixbuf));
+  g_assert (cairo_image_surface_get_height (surface) == gdk_pixbuf_get_height (pixbuf));
+
+  cairo_surface_flush (surface);
+
+  width = gdk_pixbuf_get_width (pixbuf);
+  height = gdk_pixbuf_get_height (pixbuf);
+  gdk_pixels = gdk_pixbuf_get_pixels (pixbuf);
+  gdk_rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+  n_channels = gdk_pixbuf_get_n_channels (pixbuf);
   cairo_stride = cairo_image_surface_get_stride (surface);
   cairo_pixels = cairo_image_surface_get_data (surface);
 
@@ -274,6 +261,43 @@ gdk_cairo_surface_create_from_pixbuf (const GdkPixbuf *pixbuf,
     }
 
   cairo_surface_mark_dirty (surface);
+}
+
+/**
+ * gdk_cairo_surface_create_from_pixbuf:
+ * @pixbuf: a #GdkPixbuf
+ * @scale: the scale of the new surface, or 0 to use same as @window
+ * @for_window: The window this will be drawn to, on %NULL.
+ *
+ * Creates an image surface with the same contents as
+ * the pixbuf.
+ *
+ * Returns: a new cairo surface, must be freed with cairo_surface_destroy()
+ *
+ * Since: 3.10
+ */
+cairo_surface_t *
+gdk_cairo_surface_create_from_pixbuf (const GdkPixbuf *pixbuf,
+                                      int              scale,
+                                      GdkWindow       *for_window)
+{
+  cairo_format_t format;
+  cairo_surface_t *surface;
+
+  if (gdk_pixbuf_get_n_channels (pixbuf) == 3)
+    format = CAIRO_FORMAT_RGB24;
+  else
+    format = CAIRO_FORMAT_ARGB32;
+
+  surface =
+     gdk_window_create_similar_image_surface (for_window,
+                                             format,
+                                              gdk_pixbuf_get_width (pixbuf),
+                                              gdk_pixbuf_get_height (pixbuf),
+                                             scale);
+
+  gdk_cairo_surface_paint_pixbuf (surface, pixbuf);
+
   return surface;
 }