gdk_pixbuf_get_from_window: honor device scale

gdk_pixbuf_get_from_window() paints the given window onto a new cairo
surface. Create that new surface with the same device scale as the
window so that the result is not scaled down on hidpi screens.

This is similar to 657a43e (which was reverted), but doesn't modify the
behavior of gdk_pixbuf_get_from_surface().

https://bugzilla.gnome.org/show_bug.cgi?id=757147

diff --git a/gdk/gdkpixbuf-drawable.c b/gdk/gdkpixbuf-drawable.c
index ae6e7dae8fa1f847d8cf73f23e6735079184f68f..2f780a57532f100fa4984cd4fa14bc7399e9c812 100644 (file)
--- a/gdk/gdkpixbuf-drawable.c
+++ b/gdk/gdkpixbuf-drawable.c
@@ -56,8 +56,9 @@
  * This allows you to efficiently read individual pixels on the client side.
  *
  * This function will create an RGB pixbuf with 8 bits per channel with
- * the same size specified by the @width and @height arguments. The pixbuf
- * will contain an alpha channel if the @window contains one.
+ * the size specified by the @width and @height arguments scaled by the
+ * scale factor of @window. The pixbuf will contain an alpha channel if
+ * the @window contains one.
  *
  * If the window is off the screen, then there is no image data in the
  * obscured/offscreen regions to be placed in the pixbuf. The contents of
@@ -87,6 +88,8 @@ gdk_pixbuf_get_from_window (GdkWindow *src,
                             gint       height)
 {
   cairo_surface_t *surface;
+  cairo_surface_t *copy;
+  cairo_t *cr;
   GdkPixbuf *dest;
 
   g_return_val_if_fail (GDK_IS_WINDOW (src), NULL);
@@ -101,9 +104,22 @@ gdk_pixbuf_get_from_window (GdkWindow *src,
    */
   cairo_surface_mark_dirty (surface);
 
-  dest = gdk_pixbuf_get_from_surface (surface,
-                                      src_x, src_y,
-                                      width, height);
+  if (cairo_surface_get_content (surface) & CAIRO_CONTENT_ALPHA)
+    copy = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, width * scale, height * scale);
+  else
+    copy = cairo_image_surface_create (CAIRO_FORMAT_RGB24, width * scale, height * scale);
+
+  cairo_surface_set_device_scale (copy, scale, scale);
+
+  cr = cairo_create (copy);
+  cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
+  cairo_set_source_surface (cr, surface, -src_x, -src_y);
+  cairo_paint (cr);
+  cairo_destroy (cr);
+
+  dest = gdk_pixbuf_get_from_surface (copy, 0, 0, width * scale, height * scale);
+
+  cairo_surface_destroy (copy);
   cairo_surface_destroy (surface);
 
   return dest;