xcb/glx: correct viewport position (fixes #10907)

modules/video_output/xcb/glx.c

@@ -259,7 +259,7 @@ static int Control (vout_display_t *vd, int query, va_list ap)
         vout_display_PlacePicture (&place, source, cfg, false);
 
         vlc_gl_MakeCurrent (sys->gl);
-        glViewport (0, 0, place.width, place.height);
+        glViewport (place.x, place.y, place.width, place.height);
         vlc_gl_ReleaseCurrent (sys->gl);
         return VLC_SUCCESS;
     }