Ensure the Compositor does not start during termination

Summary:
The SceneOpenGLES test was starting to randomly crash on my system. On
investigation I observed that there was a graphics reset ("Attempting to
reset compositing.") which triggered a delayed restart of the
compositor. This even was only processed while waiting for XWayland to
terminate. Which resulted in a crash in KWin::getXServerVersion as the
xcb connection broke.

It makes no sense to setup the compositor again during application
shutdown. Thus the dtors set a flag that they are terminating the
application and Compositor::setup is checking for it.

Test Plan: Test no longer crashes, although it goes through the crashing path

Reviewers: #kwin

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D18015

autotests/integration/kwin_wayland_test.cpp

@@ -76,6 +76,7 @@ WaylandTestApplication::WaylandTestApplication(OperationMode mode, int &argc, ch
 
 WaylandTestApplication::~WaylandTestApplication()
 {
+    setTerminating();
     kwinApp()->platform()->setOutputsEnabled(false);
     // need to unload all effects prior to destroying X connection as they might do X calls
     // also before destroy Workspace, as effects might call into Workspace

composite.cpp

@@ -156,6 +156,10 @@ Compositor::~Compositor()
 
 void Compositor::setup()
 {
+    if (kwinApp()->isTerminating()) {
+        // don't setup while KWin is terminating. An event to restart might be lingering in the event queue due to graphics reset
+        return;
+    }
     if (hasScene())
         return;
     if (m_suspended) {

main.h

@@ -188,6 +188,10 @@ public:
         return m_platform;
     }
 
+    bool isTerminating() const {
+        return m_terminating;
+    }
+
     static void setupMalloc();
     static void setupLocalizedString();
 
@@ -231,6 +235,10 @@ protected:
     }
     void destroyAtoms();
 
+    void setTerminating() {
+        m_terminating = true;
+    }
+
 protected:
     QString m_originalSessionKey;
     static int crashes;
@@ -252,6 +260,7 @@ private:
     bool m_useKActivities = true;
 #endif
     Platform *m_platform = nullptr;
+    bool m_terminating = false;
 };
 
 inline static Application *kwinApp()

main_wayland.cpp

@@ -129,6 +129,7 @@ ApplicationWayland::ApplicationWayland(int &argc, char **argv)
 
 ApplicationWayland::~ApplicationWayland()
 {
+    setTerminating();
     if (!waylandServer()) {
         return;
     }

main_x11.cpp

@@ -187,6 +187,7 @@ ApplicationX11::ApplicationX11(int &argc, char **argv)
 
 ApplicationX11::~ApplicationX11()
 {
+    setTerminating();
     destroyCompositor();
     destroyWorkspace();
     if (!owner.isNull() && owner->ownerWindow() != XCB_WINDOW_NONE)   // If there was no --replace (no new WM)