fix gl backing: add stub for alpha channel handling

git-svn-id: https://xpra.org/svn/Xpra/trunk@3371 3bb7dfac-3a0b-4e04-842a-767bc560f471

src/xpra/client/gl/gl_client_window.py

@@ -53,14 +53,15 @@ def new_backing(self, w, h):
         debug("GL new_backing(%s, %s)", w, h)
         w = max(2, w)
         h = max(2, h)
+        has_alpha = self._metadata.get("has-alpha", False)
         lock = None
         if self._backing:
             lock = self._backing._video_decoder_lock
         try:
             if lock:
                 lock.acquire()
             if self._backing is None:
-                self._backing = self.gl_pixmap_backing_class(self._id, w, h)
+                self._backing = self.gl_pixmap_backing_class(self._id, w, h, has_alpha)
                 if self._client.supports_mmap:
                     self._backing.enable_mmap(self._client.mmap)
             self._backing.init(w, h)

src/xpra/client/gl/gl_window_backing.py

@@ -85,8 +85,8 @@ def py_gl_debug_callback(source, error_type, error_id, severity, length, message
 """
 class GLPixmapBacking(GTK2WindowBacking):
 
-    def __init__(self, wid, w, h):
-        GTK2WindowBacking.__init__(self, wid, w, h)
+    def __init__(self, wid, w, h, has_alpha):
+        GTK2WindowBacking.__init__(self, wid, w, h, has_alpha)
         display_mode = get_DISPLAY_MODE()
         try:
             self.glconfig = gtk.gdkgl.Config(mode=display_mode)