Update SurfaceInterface outputs when an output global gets destroyed

Summary:
As per existing TODO.

A new signal is added on Global to emit so we can process the result
whist we still have a valid object. The name is overly explicit to try
and logically separate it from QObject::destroyed().

Test Plan: Updated existing unit test.

Reviewers: #plasma, graesslin

Reviewed By: #plasma, graesslin

Subscribers: graesslin, anthonyfieroni, plasma-devel, #frameworks

Tags: #frameworks, #plasma_on_wayland

Differential Revision: https://phabricator.kde.org/D7531

src/wayland/autotests/client/test_wayland_surface.cpp

@@ -1077,11 +1077,11 @@ void TestWaylandSurface::testOutput()
     QCOMPARE(enteredSpy.count(), 2);
     QCOMPARE(leftSpy.count(), 1);
 
-    //test the client handles a misbehaving server that removes a display before updating clients
-    m_display->removeOutput(serverOutput);
-    QCOMPARE(leftSpy.count(), 1);
-    QVERIFY(s->outputs().isEmpty());
-
+    //delete output client is on.
+    //client should get an exit and be left on no outputs (which is allowed)
+    serverOutput->deleteLater();
+    QVERIFY(leftSpy.wait());
+    QCOMPARE(serverSurface->outputs(), QVector<OutputInterface*>());
 }
 
 QTEST_GUILESS_MAIN(TestWaylandSurface)

src/wayland/server/global.cpp

@@ -70,6 +70,7 @@ void Global::destroy()
     if (!d->global) {
         return;
     }
+    emit aboutToDestroyGlobal();
     wl_global_destroy(d->global);
     d->global = nullptr;
 }

src/wayland/server/global.h

@@ -90,6 +90,14 @@ public:
      **/
     operator wl_global*() const;
 
+Q_SIGNALS:
+    /**
+     * This signal is emitted when the client is in the process of removing the wl_global.
+     * At the time the signal is emitted the global is still valid and allows to perform
+     * cleanup tasks.
+     */
+    void aboutToDestroyGlobal();
+
 protected:
     class Private;
     explicit Global(Private *d, QObject *parent = nullptr);

src/wayland/surface_interface.cpp

@@ -793,19 +793,25 @@ void SurfaceInterface::setOutputs(const QVector<OutputInterface *> &outputs)
         for (wl_resource *r : resources) {
             wl_surface_send_leave(d->resource, r);
         }
+        disconnect(d->outputDestroyedConnections.take(*it));
     }
-    // TODO: send leave when OutputInterface gets destroyed
-
     QVector<OutputInterface *> addedOutputsOutputs = outputs;
     for (auto it = d->outputs.constBegin(), end = d->outputs.constEnd(); it != end; ++it) {
         const auto o = *it;
         addedOutputsOutputs.removeOne(o);
     }
     for (auto it = addedOutputsOutputs.constBegin(), end = addedOutputsOutputs.constEnd(); it != end; ++it) {
-        const auto resources = (*it)->clientResources(client());
+        const auto o = *it;
+        const auto resources = o->clientResources(client());
         for (wl_resource *r : resources) {
             wl_surface_send_enter(d->resource, r);
         }
+        d->outputDestroyedConnections[o] = connect(o, &Global::aboutToDestroyGlobal, this, [this, o] {
+            Q_D();
+            auto outputs = d->outputs;
+            if (outputs.removeOne(o)) {
+                setOutputs(outputs);
+            }});
     }
     // TODO: send enter when the client binds the OutputInterface another time
 

src/wayland/surface_interface_p.h

@@ -97,6 +97,7 @@ public:
 
     QPointer<LockedPointerInterface> lockedPointer;
     QPointer<ConfinedPointerInterface> confinedPointer;
+    QHash<OutputInterface*, QMetaObject::Connection> outputDestroyedConnections;
 
 private:
     QMetaObject::Connection constrainsOneShotConnection;