[gtk+/gtk-3-18] gdk_pixbuf_get_from_window: honor device scale

[Lars Uebernickel <larsu src gnome org>]

commit a950b5357ab8541212012f44f53caf236ce5aab9
Author: Lars Uebernickel <lars uebernickel canonical com>
Date:   Mon Oct 26 10:12:34 2015 +0100

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

 gdk/gdkpixbuf-drawable.c |   17 ++++++++++++-----
 1 files changed, 12 insertions(+), 5 deletions(-)
---
diff --git a/gdk/gdkpixbuf-drawable.c b/gdk/gdkpixbuf-drawable.c
index ae6e7da..2e3de8c 100644
--- a/gdk/gdkpixbuf-drawable.c
+++ b/gdk/gdkpixbuf-drawable.c
@@ -47,8 +47,8 @@
  * @window: Source window
  * @src_x: Source X coordinate within @window
  * @src_y: Source Y coordinate within @window
- * @width: Width in pixels of region to get
- * @height: Height in pixels of region to get
+ * @width: Width in logical pixels of region to get
+ * @height: Height in logical pixels of region to get
  *
  * Transfers image data from a #GdkWindow and converts it to an RGB(A)
  * representation inside a #GdkPixbuf. In other words, copies
@@ -88,10 +88,13 @@ gdk_pixbuf_get_from_window (GdkWindow *src,
 {
   cairo_surface_t *surface;
   GdkPixbuf *dest;
+  gint scale;
 
   g_return_val_if_fail (GDK_IS_WINDOW (src), NULL);
   g_return_val_if_fail (gdk_window_is_viewable (src), NULL);
 
+  scale = gdk_window_get_scale_factor (src);
+
   surface = _gdk_window_ref_cairo_surface (src);
 
   /* We do not know what happened to this surface outside of GDK.
@@ -102,8 +105,8 @@ 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);
+                                      scale * src_x, scale * src_y,
+                                      scale * width, scale * height);
   cairo_surface_destroy (surface);
 
   return dest;
@@ -116,7 +119,6 @@ gdk_cairo_format_for_content (cairo_content_t content)
     {
     case CAIRO_CONTENT_COLOR:
       return CAIRO_FORMAT_RGB24;
-    case CAIRO_CONTENT_ALPHA:
       return CAIRO_FORMAT_A8;
     case CAIRO_CONTENT_COLOR_ALPHA:
     default:
@@ -134,11 +136,16 @@ gdk_cairo_surface_coerce_to_image (cairo_surface_t *surface,
 {
   cairo_surface_t *copy;
   cairo_t *cr;
+  double sx, sy;
+
+  cairo_surface_get_device_scale (surface, &sx, &sy);
 
   copy = cairo_image_surface_create (gdk_cairo_format_for_content (content),
                                      width,
                                      height);
 
+  cairo_surface_set_device_scale (copy, sx, sy);
+
   cr = cairo_create (copy);
   cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
   cairo_set_source_surface (cr, surface, -src_x, -src_y);