[gtk+] win32: Report ScrollDC update region directly

[Alexander Larsson <alexl src gnome org>]

commit 1884271f034ec8b3c7c4e6ffe02c04fd0e865bf9
Author: Alexander Larsson <alexl redhat com>
Date:   Thu Apr 11 12:12:35 2013 +0200

    win32: Report ScrollDC update region directly
    
    Rather than set the window update region and repaint this region
    when we get a WM_PAINT we just directly add it to the update
    region. No need to roundtrip via win32.
    
    This lets us also make sure we do this drawing in the same update
    cycle. This seems especially important on Win7, because ScrollDC
    seems to act kind of weird there, not using bitblt in areas where
    it seemingly could, which makes scrolling look really flashy.
    
    http://bugzilla.gnome.org/show_bug-cgi?id=674051

 gdk/win32/gdkwindow-win32.c |   21 +++++++++------------
 1 files changed, 9 insertions(+), 12 deletions(-)
---
diff --git a/gdk/win32/gdkwindow-win32.c b/gdk/win32/gdkwindow-win32.c
index 95f6e16..2c2e15d 100644
--- a/gdk/win32/gdkwindow-win32.c
+++ b/gdk/win32/gdkwindow-win32.c
@@ -3330,9 +3330,8 @@ _gdk_win32_window_translate (GdkWindow *window,
                              gint       dy)
 {
   GdkWindowImplWin32 *impl = GDK_WINDOW_IMPL_WIN32 (window->impl);
-  GdkRectangle extents;
-  RECT rect;
   HRGN hrgn, area_hrgn;
+  cairo_region_t *update_region;
   HDC hdc;
   int ret;
 
@@ -3367,19 +3366,17 @@ _gdk_win32_window_translate (GdkWindow *window,
   /* Clip hdc to target region */
   API_CALL (SelectClipRgn, (hdc, area_hrgn));
 
-  cairo_region_get_extents (area, &extents);
-
-  rect.left = MIN (extents.x, extents.x - dx);
-  rect.top = MIN (extents.y, extents.y - dy);
-  rect.right = MAX (extents.x + extents.width, extents.x - dx  + extents.width);
-  rect.bottom = MAX (extents.y + extents.height, extents.y - dy  + extents.height);
-
   SetRectRgn (hrgn, 0, 0, 0, 0);
 
-  if (!ScrollDC (hdc, dx, dy, &rect, NULL, hrgn, NULL))
+  if (!ScrollDC (hdc, dx, dy, NULL, NULL, hrgn, NULL))
     WIN32_GDI_FAILED ("ScrollDC");
-  else if (!InvalidateRgn (GDK_WINDOW_HWND (window), hrgn, FALSE))
-    WIN32_GDI_FAILED ("InvalidateRgn");
+  else
+    {
+      update_region = _gdk_win32_hrgn_to_region (hrgn);
+      if (!cairo_region_is_empty (update_region))
+       _gdk_window_invalidate_for_expose (window, update_region);
+      cairo_region_destroy (update_region);
+    }
 
   /* Unset hdc clip region */
   API_CALL (SelectClipRgn, (hdc, NULL));