[PATCH] winex11.drv: Maintain a backing store for layered windows.

[Zhiyi Zhang]

Copy the window content to a pixmap and set it as the background because
the X server may discard the window content at any time, even when the
backing store attribute is set to TRUE when creating a X11 window.
Layered windows don't get repainted in X11DRV_Expose() like normal
windows do and their content should always be kept. The window surface
may be recreated when handling position and changes. So for most of the
time, there is only one backing store for a window with this patch. It's
possible that the we can reuse window surfaces but it's a much bigger
change and risk breaking things.

Fix Word 2016 frame window corruption after it's moved off-screen.

Signed-off-by: Zhiyi Zhang <zzhang at codeweavers.com>
---
 dlls/winex11.drv/window.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/dlls/winex11.drv/window.c b/dlls/winex11.drv/window.c
index 7ec2639e309..c639b9d06d2 100644
--- a/dlls/winex11.drv/window.c
+++ b/dlls/winex11.drv/window.c
@@ -2706,6 +2706,9 @@ BOOL CDECL X11DRV_UpdateLayeredWindow( HWND hwnd, const UPDATELAYEREDWINDOWINFO
     HDC hdc = 0;
     HBITMAP dib;
     BOOL ret = FALSE;
+    int width, height;
+    Pixmap pixmap;
+    GC gc;
 
     if (!(data = get_win_data( hwnd ))) return FALSE;
 
@@ -2726,11 +2729,15 @@ BOOL CDECL X11DRV_UpdateLayeredWindow( HWND hwnd, const UPDATELAYEREDWINDOWINFO
     else set_surface_color_key( surface, color_key );
 
     if (surface) window_surface_add_ref( surface );
-    release_win_data( data );
 
-    if (!surface) return FALSE;
+    if (!surface)
+    {
+        release_win_data( data );
+        return FALSE;
+    }
     if (!info->hdcSrc)
     {
+        release_win_data( data );
         window_surface_release( surface );
         return TRUE;
     }
@@ -2767,7 +2774,24 @@ BOOL CDECL X11DRV_UpdateLayeredWindow( HWND hwnd, const UPDATELAYEREDWINDOWINFO
     surface->funcs->unlock( surface );
     surface->funcs->flush( surface );
 
+    /* Copy the window content to a pixmap and set it as the background because the X server may
+     * discard the window content at any time, even when the backing store attribute is set to TRUE
+     * when creating a X11 window. Layered windows don't get repainted in X11DRV_Expose() like
+     * normal windows do and their content should always be kept. */
+    width = data->whole_rect.right - data->whole_rect.left;
+    height = data->whole_rect.bottom - data->whole_rect.top;
+    if (width > 0 && height > 0)
+    {
+        pixmap = XCreatePixmap( data->display, data->whole_window, width, height, 32 );
+        gc = XCreateGC( data->display, pixmap, 0, NULL );
+        XCopyArea( data->display, data->whole_window, pixmap, gc, 0, 0, width, height, 0, 0 );
+        XFreeGC( data->display, gc );
+        XSetWindowBackgroundPixmap( data->display, data->whole_window, pixmap );
+        XFreePixmap( data->display, pixmap );
+    }
+
 done:
+    release_win_data( data );
     window_surface_release( surface );
     if (hdc) DeleteDC( hdc );
     if (dib) DeleteObject( dib );
-- 
2.32.0