From b145cc3c37423f4309654d5a0528b4e49efd7d7f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michel=20D=C3=A4nzer?= <michel.daenzer@amd.com>
Date: Mon, 8 Apr 2019 19:02:01 +0200
Subject: [PATCH] xwayland/rootless: Always paint background for toplevel
 windows

If a toplevel window has no background, temporarily use the root
window's background for it in PaintWindow.

This avoids presenting uninitialized window contents, which should fix
issue #636.
---
 hw/xwayland/xwayland.c | 38 ++++++++++++++++++++++++++++++++++++++
 hw/xwayland/xwayland.h |  1 +
 2 files changed, 39 insertions(+)

diff --git a/hw/xwayland/xwayland.c b/hw/xwayland/xwayland.c
index 739f86cf1..3e4e80dac 100644
--- a/hw/xwayland/xwayland.c
+++ b/hw/xwayland/xwayland.c
@@ -485,6 +485,39 @@ send_surface_id_event(struct xwl_window *xwl_window)
                           &e, 1, SubstructureRedirectMask, NullGrab);
 }
 
+static void
+xwl_paint_window(WindowPtr window, RegionPtr region, int what)
+{
+    ScreenPtr screen = window->drawable.pScreen;
+    struct xwl_screen *xwl_screen = xwl_screen_get(screen);
+    WindowPtr bg_window = NULL;
+
+    if (what == PW_BACKGROUND) {
+        struct xwl_window *xwl_window;
+
+        bg_window = window;
+        while (bg_window->backgroundState == ParentRelative)
+            bg_window = bg_window->parent;
+
+        /* If a toplevel window has background None, temporarily set it to
+         * ParentRelative, so the root window's background will be used
+         */
+        xwl_window = xwl_window_get(bg_window);
+        if (xwl_window && bg_window->backgroundState == None)
+            bg_window->backgroundState = ParentRelative;
+        else
+            bg_window = NULL;
+    }
+
+    screen->PaintWindow = xwl_screen->PaintWindow;
+    (*screen->PaintWindow) (window, region, what);
+    xwl_screen->PaintWindow = screen->PaintWindow;
+    screen->PaintWindow = xwl_paint_window;
+
+    if (bg_window)
+        bg_window->backgroundState = None;
+}
+
 static Bool
 xwl_realize_window(WindowPtr window)
 {
@@ -1092,6 +1125,11 @@ xwl_screen_init(ScreenPtr pScreen, int argc, char **argv)
         pScreen->DestroyPixmap = xwl_shm_destroy_pixmap;
     }
 
+    if (xwl_screen->rootless) {
+        xwl_screen->PaintWindow = pScreen->PaintWindow;
+        pScreen->PaintWindow = xwl_paint_window;
+    }
+
     xwl_screen->RealizeWindow = pScreen->RealizeWindow;
     pScreen->RealizeWindow = xwl_realize_window;
 
diff --git a/hw/xwayland/xwayland.h b/hw/xwayland/xwayland.h
index 92664e812..73fc5b2e4 100644
--- a/hw/xwayland/xwayland.h
+++ b/hw/xwayland/xwayland.h
@@ -126,6 +126,7 @@ struct xwl_screen {
 
     CreateScreenResourcesProcPtr CreateScreenResources;
     CloseScreenProcPtr CloseScreen;
+    PaintWindowProcPtr PaintWindow;
     RealizeWindowProcPtr RealizeWindow;
     UnrealizeWindowProcPtr UnrealizeWindow;
     DestroyWindowProcPtr DestroyWindow;
-- 
GitLab