GDK W32: Update layered windows on opacity changes

Without this patch layered windows are only updated when they are moved
by the user or then their contents changes. This patch adds opacity
changes to the list of things that make GDK update a window. Without this
windows that don't redraw and are not moved by the used (DnD drag indicator
windows, for example) don't change their opacity.

https://bugzilla.gnome.org/show_bug.cgi?id=786509

1 files changed, 118 insertions, 68 deletions

diff --git a/gdk/win32/gdkwindow-win32.c b/gdk/win32/gdkwindow-win32.c
index 53672a7d6e..bb92f0e5d9 100644
--- a/gdk/win32/gdkwindow-win32.c
+++ b/gdk/win32/gdkwindow-win32.c
@@ -260,18 +260,29 @@ gdk_window_impl_win32_finalize (GObject *object)
 }
 
 static void
+gdk_win32_get_window_client_area_rect (GdkWindow *window,
+                                       gint       scale,
+                                       RECT      *rect)
+{
+  gint x, y, width, height;
+
+  gdk_window_get_position (window, &x, &y);
+  width = gdk_window_get_width (window);
+  height = gdk_window_get_height (window);
+  rect->left = x * scale;
+  rect->top = y * scale;
+  rect->right = rect->left + width * scale;
+  rect->bottom = rect->top + height * scale;
+}
+
+static void
 gdk_win32_window_get_queued_window_rect (GdkWindow *window,
                                          RECT      *return_window_rect)
 {
-  gint x, y;
   RECT window_rect;
   GdkWindowImplWin32 *impl = GDK_WINDOW_IMPL_WIN32 (window->impl);
 
-  gdk_window_get_position (window, &x, &y);
-  window_rect.left = x * impl->window_scale;
-  window_rect.top = y * impl->window_scale;
-  window_rect.right = window_rect.left + gdk_window_get_width (window) * impl->window_scale;
-  window_rect.bottom = window_rect.top + gdk_window_get_height (window) * impl->window_scale;
+  gdk_win32_get_window_client_area_rect (window, impl->window_scale, &window_rect);
 
   /* Turn client area into window area */
   _gdk_win32_adjust_client_rect (window, &window_rect);
@@ -4782,6 +4793,83 @@ gdk_win32_window_end_move_resize_drag (GdkWindow *window)
   context->current_snap = GDK_WIN32_AEROSNAP_STATE_UNDETERMINED;
 }
 
+static void
+gdk_win32_get_window_size_and_position_from_client_rect (GdkWindow *window,
+                                                         RECT      *window_rect,
+                                                         SIZE      *window_size,
+                                                         POINT     *window_position)
+{
+  GdkWindowImplWin32 *impl;
+
+  impl = GDK_WINDOW_IMPL_WIN32 (window->impl);
+
+  /* Turn client area into window area */
+  _gdk_win32_adjust_client_rect (window, window_rect);
+
+  /* Convert GDK screen coordinates to W32 desktop coordinates */
+  window_rect->left -= _gdk_offset_x * impl->window_scale;
+  window_rect->right -= _gdk_offset_x * impl->window_scale;
+  window_rect->top -= _gdk_offset_y * impl->window_scale;
+  window_rect->bottom -= _gdk_offset_y * impl->window_scale;
+
+  window_position->x = window_rect->left;
+  window_position->y = window_rect->top;
+  window_size->cx = window_rect->right - window_rect->left;
+  window_size->cy = window_rect->bottom - window_rect->top;
+}
+
+static void
+gdk_win32_update_layered_window_from_cache (GdkWindow *window,
+                                            RECT      *client_rect)
+{
+  POINT window_position;
+  SIZE window_size;
+  BLENDFUNCTION blender;
+  HDC hdc;
+  SIZE *window_size_ptr;
+  POINT source_point = { 0, 0 };
+  POINT *source_point_ptr;
+  GdkWindowImplWin32 *impl;
+
+  impl = GDK_WINDOW_IMPL_WIN32 (window->impl);
+
+  gdk_win32_get_window_size_and_position_from_client_rect (window,
+                                                           client_rect,
+                                                           &window_size,
+                                                           &window_position);
+
+  blender.BlendOp = AC_SRC_OVER;
+  blender.BlendFlags = 0;
+  blender.AlphaFormat = AC_SRC_ALPHA;
+  blender.SourceConstantAlpha = impl->layered_opacity * 255;
+
+  /* Size didn't change, so move immediately, no need to wait for redraw */
+  /* Strictly speaking, we don't need to supply hdc, source_point and
+   * window_size here. However, without these arguments
+   * the window moves but does not update its contents on Windows 7 when
+   * desktop composition is off. This forces us to provide hdc and
+   * source_point. window_size is here to avoid the function
+   * inexplicably failing with error 317.
+   */
+  if (gdk_screen_is_composited (gdk_window_get_screen (window)))
+    {
+      hdc = NULL;
+      window_size_ptr = NULL;
+      source_point_ptr = NULL;
+    }
+  else
+    {
+      hdc = cairo_win32_surface_get_dc (impl->cache_surface);
+      window_size_ptr = &window_size;
+      source_point_ptr = &source_point;
+    }
+
+  API_CALL (UpdateLayeredWindow, (GDK_WINDOW_HWND (window), NULL,
+                                  &window_position, window_size_ptr,
+                                  hdc, source_point_ptr,
+                                  0, &blender, ULW_ALPHA));
+}
+
 void
 gdk_win32_window_do_move_resize_drag (GdkWindow *window,
                                       gint       x,
@@ -4958,67 +5046,24 @@ gdk_win32_window_do_move_resize_drag (GdkWindow *window,
            (rect.left != new_rect.left ||
             rect.top != new_rect.top))
     {
-      POINT window_position;
-      SIZE window_size;
-      BLENDFUNCTION blender;
-      HDC hdc;
-      SIZE *window_size_ptr;
-      POINT source_point = { 0, 0 };
-      POINT *source_point_ptr;
-
       context->native_move_resize_pending = FALSE;
 
       _gdk_win32_do_emit_configure_event (window, new_rect);
 
-      /* Turn client area into window area */
-      _gdk_win32_adjust_client_rect (window, &new_rect);
-
-      /* Convert GDK screen coordinates to W32 desktop coordinates */
-      new_rect.left -= _gdk_offset_x * impl->window_scale;
-      new_rect.right -= _gdk_offset_x * impl->window_scale;
-      new_rect.top -= _gdk_offset_y * impl->window_scale;
-      new_rect.bottom -= _gdk_offset_y * impl->window_scale;
-
-      window_position.x = new_rect.left;
-      window_position.y = new_rect.top;
-      window_size.cx = new_rect.right - new_rect.left;
-      window_size.cy = new_rect.bottom - new_rect.top;
-
-      blender.BlendOp = AC_SRC_OVER;
-      blender.BlendFlags = 0;
-      blender.AlphaFormat = AC_SRC_ALPHA;
-      blender.SourceConstantAlpha = impl->layered_opacity * 255;
-
-      /* Size didn't change, so move immediately, no need to wait for redraw */
-      /* Strictly speaking, we don't need to supply hdc, source_point and
-       * window_size here. However, without these arguments
-       * the window moves but does not update its contents on Windows 7 when
-       * desktop composition is off. This forces us to provide hdc and
-       * source_point. window_size is here to avoid the function
-       * inexplicably failing with error 317.
-       */
       if (impl->layered)
         {
-          if (gdk_screen_is_composited (gdk_window_get_screen (window)))
-            {
-              hdc = NULL;
-              window_size_ptr = NULL;
-              source_point_ptr = NULL;
-            }
-          else
-            {
-              hdc = cairo_win32_surface_get_dc (impl->cache_surface);
-              window_size_ptr = &window_size;
-              source_point_ptr = &source_point;
-            }
-
-          API_CALL (UpdateLayeredWindow, (GDK_WINDOW_HWND (window), NULL,
-                                          &window_position, window_size_ptr,
-                                          hdc, source_point_ptr,
-                                          0, &blender, ULW_ALPHA));
+          gdk_win32_update_layered_window_from_cache (window, &new_rect);
         }
       else
         {
+          SIZE window_size;
+          POINT window_position;
+
+          gdk_win32_get_window_size_and_position_from_client_rect (window,
+                                                                   &new_rect,
+                                                                   &window_size,
+                                                                   &window_position);
+
           API_CALL (SetWindowPos, (GDK_WINDOW_HWND (window),
                                    SWP_NOZORDER_SPECIFIED,
                                    window_position.x, window_position.y,
@@ -5626,11 +5671,20 @@ gdk_win32_window_set_opacity (GdkWindow *window,
 
   impl = GDK_WINDOW_IMPL_WIN32 (window->impl);
 
-  impl->layered_opacity = opacity;
-
   if (impl->layered)
-    /* Layered windows have opacity applied elsewhere */
-    return;
+    {
+      if (impl->layered_opacity != opacity)
+        {
+          RECT window_rect;
+
+          impl->layered_opacity = opacity;
+
+          gdk_win32_get_window_client_area_rect (window, impl->window_scale, &window_rect);
+          gdk_win32_update_layered_window_from_cache (window, &window_rect);
+        }
+
+      return;
+    }
 
   exstyle = GetWindowLong (GDK_WINDOW_HWND (window), GWL_EXSTYLE);
 
@@ -5812,14 +5866,10 @@ static cairo_surface_t *
 gdk_win32_ref_cairo_surface_layered (GdkWindow          *window,
                                      GdkWindowImplWin32 *impl)
 {
-  gint x, y, width, height;
+  gint width, height;
   RECT window_rect;
 
-  gdk_window_get_position (window, &x, &y);
-  window_rect.left = x * impl->window_scale;
-  window_rect.top = y * impl->window_scale;
-  window_rect.right = window_rect.left + gdk_window_get_width (window) * impl->window_scale;
-  window_rect.bottom = window_rect.top + gdk_window_get_height (window) * impl->window_scale;
+  gdk_win32_get_window_client_area_rect (window, impl->window_scale, &window_rect);
 
   /* Turn client area into window area */
   _gdk_win32_adjust_client_rect (window, &window_rect);