From 04ccf04596a0c0e95e5c520af87745dfb3425dd8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Gr=C3=A4=C3=9Flin?= <mgraesslin@kde.org>
Date: Wed, 23 Mar 2016 17:01:39 +0100
Subject: [PATCH] [server] Add a workaround for a freeze in QtWayland

Summary:
See: https://bugreports.qt.io/browse/QTBUG-52092

Freeze happens if a sub-surface is rendered to before the main surface
is rendered. The compositor has no chance to know that this is a window
which needs to be rendered, thus the application might freeze without
ever becoming visible.

Famous example applications being affected: all kcms with a nested
QQuickView. E.g.: kcmshell5 kwineffects

Reviewers: #plasma

Subscribers: plasma-devel

Projects: #plasma

Differential Revision: https://phabricator.kde.org/D1208
---
 src/wayland/surface_interface.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/wayland/surface_interface.cpp b/src/wayland/surface_interface.cpp
index 8338f8da56..82d48469fe 100644
--- a/src/wayland/surface_interface.cpp
+++ b/src/wayland/surface_interface.cpp
@@ -338,6 +338,11 @@ void SurfaceInterface::Private::swapStates(State *source, State *target, bool em
                 target->damage = windowRegion.intersected(target->damage);
                 if (emitChanged) {
                     emit q->damaged(target->damage);
+                    // workaround for https://bugreports.qt.io/browse/QTBUG-52092
+                    // if the surface is a sub-surface, but the main surface is not yet mapped, fake frame rendered
+                    if (subSurface && !subSurface->mainSurface()->buffer()) {
+                        q->frameRendered(0);
+                    }
                 }
             }
         } else if (!target->buffer && emitChanged) {