Add functionality to set overall opacity of a top-level window. (#405316)

2007-04-30  Tor Lillqvist  <tml@novell.com>

	Add functionality to set overall opacity of a top-level
	window. (#405316)

	* gdk/gdk.symbols: Add gdk_window_set_opacity.

	* gdk/x11/gdkwindow-x11.c
	* gdk/win32/gdkwindow-win32.c: Implement
	gdk_window_set_opacity(). On X11 use the _NET_WM_WINDOW_OPACITY
	property. On Win32 use SetLayeredWindowAttributes(LWA_ALPHA).

	* gdk/gdkwindow.h: Declare gdk_window_set_opacity().

	* gdk/x11/gdkscreen-x11.c (gdk_screen_get_rgba_colormap): Document
	that this is not implemented in the Windows backend. Add reference
	to gdk_window_set_opacity().


svn path=/trunk/; revision=17730

5 files changed, 88 insertions, 2 deletions

diff --git a/gdk/gdk.symbols b/gdk/gdk.symbols
index b064cc7f5..ae3458654 100644
--- a/gdk/gdk.symbols
+++ b/gdk/gdk.symbols
@@ -740,6 +740,7 @@ gdk_window_set_icon_list
 gdk_window_set_icon
 gdk_window_set_icon_name
 gdk_window_beep
+gdk_window_set_opacity
 gdk_window_iconify
 gdk_window_deiconify
 gdk_window_stick
diff --git a/gdk/gdkwindow.h b/gdk/gdkwindow.h
index 325c4b3d8..9ff3a09fc 100644
--- a/gdk/gdkwindow.h
+++ b/gdk/gdkwindow.h
@@ -569,7 +569,8 @@ void          gdk_window_set_keep_above  (GdkWindow       *window,
                                           gboolean         setting);
 void          gdk_window_set_keep_below  (GdkWindow       *window,
                                           gboolean         setting);
-
+void          gdk_window_set_opacity     (GdkWindow       *window,
+                                          gdouble          opacity);
 void          gdk_window_register_dnd    (GdkWindow       *window);
 
 void gdk_window_begin_resize_drag (GdkWindow     *window,
diff --git a/gdk/win32/gdkwindow-win32.c b/gdk/win32/gdkwindow-win32.c
index 9d029619a..75d944d2d 100644
--- a/gdk/win32/gdkwindow-win32.c
+++ b/gdk/win32/gdkwindow-win32.c
@@ -3399,3 +3399,33 @@ gdk_window_beep (GdkWindow *window)
 {
   gdk_display_beep (_gdk_display);
 }
+
+void
+gdk_window_set_opacity (GdkWindow *window,
+			gdouble    opacity)
+{
+  LONG exstyle;
+
+  g_return_if_fail (GDK_IS_WINDOW (window));
+  g_return_if_fail (WINDOW_IS_TOPLEVEL (window));
+
+  if (GDK_WINDOW_DESTROYED (window))
+    return;
+
+  if (opacity < 0)
+    opacity = 0;
+  else if (opacity > 1)
+    opacity = 1;
+
+  exstyle = GetWindowLong (GDK_WINDOW_HWND (window), GWL_EXSTYLE);
+
+  if (!(exstyle & WS_EX_LAYERED))
+    API_CALL (SetWindowLong, (GDK_WINDOW_HWND (window),
+			      GWL_EXSTYLE,
+			      exstyle | WS_EX_LAYERED));
+
+  API_CALL (SetLayeredWindowAttributes, (GDK_WINDOW_HWND (window),
+					 0,
+					 opacity * 0xff,
+					 LWA_ALPHA));
+}
diff --git a/gdk/x11/gdkscreen-x11.c b/gdk/x11/gdkscreen-x11.c
index f5e08d87a..624870f85 100644
--- a/gdk/x11/gdkscreen-x11.c
+++ b/gdk/x11/gdkscreen-x11.c
@@ -382,7 +382,12 @@ gdk_screen_get_monitor_geometry (GdkScreen    *screen,
  * when displaying the window on the screen: in particular, for
  * X an appropriate windowing manager and compositing manager
  * must be running to provide appropriate display.
- * 
+ *
+ * This functionality is not implemented in the Windows backend.
+ *
+ * For setting an overall opacity for a top-level window, see
+ * gdk_window_set_opacity().
+
  * Return value: a colormap to use for windows with an alpha channel
  *   or %NULL if the capability is not available.
  *
diff --git a/gdk/x11/gdkwindow-x11.c b/gdk/x11/gdkwindow-x11.c
index fe5a0976f..621d3245d 100644
--- a/gdk/x11/gdkwindow-x11.c
+++ b/gdk/x11/gdkwindow-x11.c
@@ -6402,5 +6402,54 @@ gdk_window_beep (GdkWindow *window)
     gdk_display_beep (display);
 }
 
+/**
+ * gdk_window_set_opacity:
+ * @window a top-level #GdkWindow
+ * @opacity: opacity
+ *
+ * Request the windowing system to make @window partially transparent,
+ * with opacity 0 being fully transparent and 1 fully opaque. (Values
+ * of the opacity parameter are clamped to the [0,1] range.) On X11
+ * this works only on X screens with a compositing manager running.
+ *
+ * For setting up per-pixel alpha, see gdk_screen_get_rgba_colormap().
+ *
+ * Since: 2.12
+ */
+void
+gdk_window_set_opacity (GdkWindow *window,
+			gdouble    opacity)
+{
+  GdkDisplay *display;
+  guint32 cardinal;
+  
+  g_return_if_fail (GDK_IS_WINDOW (window));
+  g_return_if_fail (WINDOW_IS_TOPLEVEL (window));
+
+  if (GDK_WINDOW_DESTROYED (window))
+    return;
+
+  display = gdk_drawable_get_display (window);
+
+  if (opacity < 0)
+    opacity = 0;
+  else if (opacity > 1)
+    opacity = 1;
+
+  cardinal = opacity * 0xffffffff;
+
+  if (cardinal == 0xffffffff)
+    XDeleteProperty (GDK_DISPLAY_XDISPLAY (display),
+		     GDK_WINDOW_XID (window),
+		     gdk_x11_get_xatom_by_name_for_display (display, "_NET_WM_WINDOW_OPACITY"));
+  else
+    XChangeProperty (GDK_DISPLAY_XDISPLAY (display),
+		     GDK_WINDOW_XID (window),
+		     gdk_x11_get_xatom_by_name_for_display (display, "_NET_WM_WINDOW_OPACITY"),
+		     XA_CARDINAL, 32,
+		     PropModeReplace,
+		     (guchar *) cardinal, 1);
+}
+
 #define __GDK_WINDOW_X11_C__
 #include "gdkaliasdef.c"