Refactor the attempt to surpress Application state changes when focus…

… switches between app surfaces

src/ubuntumirclient/window.cpp

@@ -27,7 +27,6 @@
 #include <qpa/qwindowsysteminterface.h>
 #include <QMutexLocker>
 #include <QSize>
-#include <QAtomicInt>
 #include <QtMath>
 #include <private/qeglconvenience_p.h>
 #include <private/qguiapplication_p.h>
@@ -401,7 +400,6 @@ class UbuntuSurface
     QSurfaceFormat format() const { return mFormat; }
 
     bool mNeedsExposeCatchup;
-    QAtomicInt mPendingFocusGainedEvents;
 
     QString persistentSurfaceId();
 
@@ -566,14 +564,6 @@ void UbuntuSurface::postEvent(const MirEvent *event)
         QMutexLocker lock(&mTargetSizeMutex);
         mTargetSize.rwidth() = width;
         mTargetSize.rheight() = height;
-    } else if (mir_event_type_surface == eventType) {
-        auto surfaceEvent = mir_event_get_surface_event(event);
-        if (mir_surface_attrib_focus == mir_surface_event_get_attribute(surfaceEvent)) {
-            const bool focused = mir_surface_event_get_attribute_value(surfaceEvent) == mir_surface_focused;
-            if (focused) {
-                mPendingFocusGainedEvents++;
-            }
-        }
     }
 
     mInput->postEvent(mPlatformWindow, event);
@@ -661,28 +651,34 @@ void UbuntuWindow::handleSurfaceExposeChange(bool exposed)
 
 void UbuntuWindow::handleSurfaceFocusChanged(bool focused)
 {
-    qCDebug(ubuntumirclient, "handleSurfaceFocusChanged(window=%p, focused=%d, pending=%d)", window(), focused, mSurface->mPendingFocusGainedEvents.load());
+    qCDebug(ubuntumirclient, "handleSurfaceFocusChanged(window=%p, focused=%d)", window(), focused);
 
-    // Mir may have sent a pair of focus lost/gained events, so we need to "peek" into the queue
-    // so that we don't deactivate windows prematurely.
     if (focused) {
-        mSurface->mPendingFocusGainedEvents--;
-        QWindowSystemInterface::handleWindowActivated(window(), Qt::ActiveWindowFocusReason);
+        // Check if Mir previously sent an unfocus event to another Window, and if so, remove it from the queue
+        // as Qt is happier if focus just transferred
+        auto *queuedActiveWindowEvent =
+            static_cast<QWindowSystemInterfacePrivate::ActivatedWindowEvent *>
+            (QWindowSystemInterfacePrivate::peekWindowSystemEvent(QWindowSystemInterfacePrivate::ActivatedWindow));
+
+        if (queuedActiveWindowEvent && !queuedActiveWindowEvent->activated) {
+            QWindowSystemInterfacePrivate::removeWindowSystemEvent(queuedActiveWindowEvent);
+        }
 
-        // NB: Since processing of system events is queued, never check qGuiApp->applicationState()
-        //     as it might be outdated. Always call handleApplicationStateChanged() with the latest
-        //     state regardless.
-        QWindowSystemInterface::handleApplicationStateChanged(Qt::ApplicationActive);
+        // Similarly, check if an ApplicationInactive event is in the queue, and remove it if so.
+        auto *queuedApplicationStateEvent =
+            static_cast<QWindowSystemInterfacePrivate::ApplicationStateChangedEvent *>
+            (QWindowSystemInterfacePrivate::peekWindowSystemEvent(QWindowSystemInterfacePrivate::ApplicationStateChanged));
 
-        // Flush events so that we update QGuiApplicationPrivate::focus_window immediately
-        QWindowSystemInterface::flushWindowSystemEvents();
+        if (queuedApplicationStateEvent && queuedApplicationStateEvent->newState == Qt::ApplicationInactive) {
+            QWindowSystemInterfacePrivate::removeWindowSystemEvent(queuedApplicationStateEvent);
+        } else {
+            QWindowSystemInterface::handleApplicationStateChanged(Qt::ApplicationActive);
+        }
 
-    } else if (mSurface->mPendingFocusGainedEvents == 0 && window() == QGuiApplicationPrivate::focus_window) {
+        QWindowSystemInterface::handleWindowActivated(window(), Qt::ActiveWindowFocusReason);
+    } else {
         QWindowSystemInterface::handleWindowActivated(nullptr, Qt::ActiveWindowFocusReason);
         QWindowSystemInterface::handleApplicationStateChanged(Qt::ApplicationInactive);
-
-        // Flush events so that we update QGuiApplicationPrivate::focus_window immediately
-        QWindowSystemInterface::flushWindowSystemEvents();
     }
 }