Use xdg_shell configure events to determine active window

According to the xdg_shell protocol, the compositor is allowed to set multiple
active windows. Qt's model, however, allows only a single active window.

In order to map between the models, a list of the compositor's active windows
is kept in QWaylandDisplay in the order they were activated. Hence, the front
of this list will always be the most recently activated window, and it will be
mapped as Qt's active window.

Previously keyboard focus was used to determine the active window, this method
has been disabled for xdg_shell.

Functionality for delaying the call to
QWindowSystemInterface::handleWindowActivated has been moved from
QWaylandInputDevice::Keyboard to QWaylandDisplay so the implementations can
share the workaround.

Task-number: QTBUG-53702
Change-Id: I878151f9c52ed09a8d6571c6208920436c3ca8fc
Reviewed-by: Giulio Camuffo <giulio.camuffo@kdab.com>

6 files changed, 100 insertions, 36 deletions

diff --git a/src/client/qwaylanddisplay.cpp b/src/client/qwaylanddisplay.cpp
index 4358bf69f..f6d86bb39 100644
--- a/src/client/qwaylanddisplay.cpp
+++ b/src/client/qwaylanddisplay.cpp
@@ -130,6 +130,8 @@ QWaylandDisplay::QWaylandDisplay(QWaylandIntegration *waylandIntegration)
     , mLastInputSerial(0)
     , mLastInputDevice(0)
     , mLastInputWindow(0)
+    , mLastKeyboardFocus(Q_NULLPTR)
+    , mSyncCallback(Q_NULLPTR)
 {
     qRegisterMetaType<uint32_t>("uint32_t");
 
@@ -383,6 +385,73 @@ void QWaylandDisplay::setLastInputDevice(QWaylandInputDevice *device, uint32_t s
     mLastInputWindow = win;
 }
 
+bool QWaylandDisplay::shellManagesActiveState() const
+{
+    //TODO: This should be part of a shell interface used by the shell protocol implementations
+    return mShellXdg;
+}
+
+void QWaylandDisplay::handleWindowActivated(QWaylandWindow *window)
+{
+    if (mActiveWindows.contains(window))
+        return;
+
+    mActiveWindows.append(window);
+    requestWaylandSync();
+}
+
+void QWaylandDisplay::handleWindowDeactivated(QWaylandWindow *window)
+{
+    Q_ASSERT(!mActiveWindows.empty());
+
+    if (mActiveWindows.last() == window)
+        requestWaylandSync();
+
+    mActiveWindows.removeOne(window);
+}
+
+void QWaylandDisplay::handleKeyboardFocusChanged(QWaylandInputDevice *inputDevice)
+{
+    QWaylandWindow *keyboardFocus = inputDevice->keyboardFocus();
+
+    if (!shellManagesActiveState() && mLastKeyboardFocus != keyboardFocus) {
+        if (keyboardFocus)
+            handleWindowActivated(keyboardFocus);
+        if (mLastKeyboardFocus)
+            handleWindowDeactivated(mLastKeyboardFocus);
+    }
+    mLastKeyboardFocus = inputDevice->keyboardFocus();
+}
+
+void QWaylandDisplay::handleWaylandSync()
+{
+    // This callback is used to set the window activation because we may get an activate/deactivate
+    // pair, and the latter one would be lost in the QWindowSystemInterface queue, if we issue the
+    // handleWindowActivated() calls immediately.
+    QWindow *activeWindow = mActiveWindows.empty() ? Q_NULLPTR : mActiveWindows.last()->window();
+    if (activeWindow != QGuiApplication::focusWindow())
+        QWindowSystemInterface::handleWindowActivated(activeWindow);
+}
+
+const wl_callback_listener QWaylandDisplay::syncCallbackListener = {
+    [](void *data, struct wl_callback *callback, uint32_t time){
+        Q_UNUSED(time);
+        wl_callback_destroy(callback);
+        QWaylandDisplay *display = static_cast<QWaylandDisplay *>(data);
+        display->mSyncCallback = Q_NULLPTR;
+        display->handleWaylandSync();
+    }
+};
+
+void QWaylandDisplay::requestWaylandSync()
+{
+    if (mSyncCallback)
+        return;
+
+    mSyncCallback = wl_display_sync(mDisplay);
+    wl_callback_add_listener(mSyncCallback, &syncCallbackListener, this);
+}
+
 }
 
 QT_END_NAMESPACE
diff --git a/src/client/qwaylanddisplay_p.h b/src/client/qwaylanddisplay_p.h
index adc012b53..237be5b78 100644
--- a/src/client/qwaylanddisplay_p.h
+++ b/src/client/qwaylanddisplay_p.h
@@ -48,6 +48,7 @@
 #include <QtCore/QObject>
 #include <QtCore/QRect>
 #include <QtCore/QPointer>
+#include <QtCore/QVector>
 
 #include <QtCore/QWaitCondition>
 
@@ -168,6 +169,11 @@ public:
     QWaylandWindow *lastInputWindow() const;
     void setLastInputDevice(QWaylandInputDevice *device, uint32_t serial, QWaylandWindow *window);
 
+    bool shellManagesActiveState() const;
+    void handleWindowActivated(QWaylandWindow *window);
+    void handleWindowDeactivated(QWaylandWindow *window);
+    void handleKeyboardFocusChanged(QWaylandInputDevice *inputDevice);
+
 public slots:
     void blockingReadEvents();
     void flushRequests();
@@ -177,6 +183,9 @@ private:
     void exitWithError();
     void checkError() const;
 
+    void handleWaylandSync();
+    void requestWaylandSync();
+
     struct Listener {
         RegistryListener listener;
         void *data;
@@ -207,6 +216,10 @@ private:
     uint32_t mLastInputSerial;
     QWaylandInputDevice *mLastInputDevice;
     QPointer<QWaylandWindow> mLastInputWindow;
+    QWaylandWindow *mLastKeyboardFocus;
+    QVector<QWaylandWindow *> mActiveWindows;
+    struct wl_callback *mSyncCallback;
+    static const wl_callback_listener syncCallbackListener;
 
     void registry_global(uint32_t id, const QString &interface, uint32_t version) Q_DECL_OVERRIDE;
     void registry_global_remove(uint32_t id) Q_DECL_OVERRIDE;
diff --git a/src/client/qwaylandinputdevice.cpp b/src/client/qwaylandinputdevice.cpp
index e2412eaa4..5eaed9ea1 100644
--- a/src/client/qwaylandinputdevice.cpp
+++ b/src/client/qwaylandinputdevice.cpp
@@ -69,7 +69,6 @@ QWaylandInputDevice::Keyboard::Keyboard(QWaylandInputDevice *p)
     , mXkbMap(0)
     , mXkbState(0)
 #endif
-    , mFocusCallback(0)
     , mNativeModifiers(0)
 {
     connect(&mRepeatTimer, SIGNAL(timeout()), this, SLOT(repeatKey()));
@@ -122,8 +121,6 @@ QWaylandInputDevice::Keyboard::~Keyboard()
 #endif
     if (mFocus)
         QWindowSystemInterface::handleWindowActivated(0);
-    if (mFocusCallback)
-        wl_callback_destroy(mFocusCallback);
     if (mParent->mVersion >= 3)
         wl_keyboard_release(object());
     else
@@ -591,10 +588,7 @@ void QWaylandInputDevice::Keyboard::keyboard_enter(uint32_t time, struct wl_surf
     QWaylandWindow *window = QWaylandWindow::fromWlSurface(surface);
     mFocus = window;
 
-    if (!mFocusCallback) {
-        mFocusCallback = wl_display_sync(mParent->mDisplay);
-        wl_callback_add_listener(mFocusCallback, &QWaylandInputDevice::Keyboard::callback, this);
-    }
+    mParent->mQDisplay->handleKeyboardFocusChanged(mParent);
 }
 
 void QWaylandInputDevice::Keyboard::keyboard_leave(uint32_t time, struct wl_surface *surface)
@@ -609,31 +603,9 @@ void QWaylandInputDevice::Keyboard::keyboard_leave(uint32_t time, struct wl_surf
 
     mFocus = NULL;
 
-    // Use a callback to set the focus because we may get a leave/enter pair, and
-    // the latter one would be lost in the QWindowSystemInterface queue, if
-    // we issue the handleWindowActivated() calls immediately.
-    if (!mFocusCallback) {
-        mFocusCallback = wl_display_sync(mParent->mDisplay);
-        wl_callback_add_listener(mFocusCallback, &QWaylandInputDevice::Keyboard::callback, this);
-    }
-    mRepeatTimer.stop();
-}
-
-const wl_callback_listener QWaylandInputDevice::Keyboard::callback = {
-    QWaylandInputDevice::Keyboard::focusCallback
-};
+    mParent->mQDisplay->handleKeyboardFocusChanged(mParent);
 
-void QWaylandInputDevice::Keyboard::focusCallback(void *data, struct wl_callback *callback, uint32_t time)
-{
-    Q_UNUSED(time);
-    Q_UNUSED(callback);
-    QWaylandInputDevice::Keyboard *self = static_cast<QWaylandInputDevice::Keyboard *>(data);
-    if (self->mFocusCallback) {
-        wl_callback_destroy(self->mFocusCallback);
-        self->mFocusCallback = 0;
-    }
-
-    QWindowSystemInterface::handleWindowActivated(self->mFocus ? self->mFocus->window() : 0);
+    mRepeatTimer.stop();
 }
 
 void QWaylandInputDevice::Keyboard::keyboard_key(uint32_t serial, uint32_t time, uint32_t key, uint32_t state)
diff --git a/src/client/qwaylandinputdevice_p.h b/src/client/qwaylandinputdevice_p.h
index 1df90292b..e38ad2f84 100644
--- a/src/client/qwaylandinputdevice_p.h
+++ b/src/client/qwaylandinputdevice_p.h
@@ -185,7 +185,6 @@ public:
     xkb_keymap *mXkbMap;
     xkb_state *mXkbState;
 #endif
-    struct wl_callback *mFocusCallback;
     uint32_t mNativeModifiers;
 
     int mRepeatKey;
@@ -197,9 +196,6 @@ public:
 #endif
     QTimer mRepeatTimer;
 
-    static const wl_callback_listener callback;
-    static void focusCallback(void *data, struct wl_callback *callback, uint32_t time);
-
     Qt::KeyboardModifiers modifiers() const;
 
 private slots:
diff --git a/src/client/qwaylandxdgsurface.cpp b/src/client/qwaylandxdgsurface.cpp
index 8852d2dfb..bbda03dc3 100644
--- a/src/client/qwaylandxdgsurface.cpp
+++ b/src/client/qwaylandxdgsurface.cpp
@@ -52,6 +52,7 @@ QWaylandXdgSurface::QWaylandXdgSurface(struct ::xdg_surface *xdg_surface, QWayla
     , m_maximized(false)
     , m_minimized(false)
     , m_fullscreen(false)
+    , m_active(false)
     , m_extendedWindow(Q_NULLPTR)
 {
     if (window->display()->windowExtension())
@@ -60,6 +61,9 @@ QWaylandXdgSurface::QWaylandXdgSurface(struct ::xdg_surface *xdg_surface, QWayla
 
 QWaylandXdgSurface::~QWaylandXdgSurface()
 {
+    if (m_active)
+        window()->display()->handleWindowDeactivated(m_window);
+
     xdg_surface_destroy(object());
     delete m_extendedWindow;
 }
@@ -176,6 +180,7 @@ void QWaylandXdgSurface::xdg_surface_configure(int32_t width, int32_t height, st
     size_t numStates = states->size / sizeof(uint32_t);
     bool aboutToMaximize = false;
     bool aboutToFullScreen = false;
+    bool aboutToActivate = false;
 
     for (size_t i = 0; i < numStates; i++) {
         switch (state[i]) {
@@ -189,13 +194,21 @@ void QWaylandXdgSurface::xdg_surface_configure(int32_t width, int32_t height, st
             m_normalSize = QSize(width, height);
             break;
         case XDG_SURFACE_STATE_ACTIVATED:
-            // TODO: here about the missing window activation
+            aboutToActivate = true;
             break;
         default:
             break;
         }
     }
 
+    if (!m_active && aboutToActivate) {
+        m_active = true;
+        window()->display()->handleWindowActivated(m_window);
+    } else if (m_active && !aboutToActivate) {
+        m_active = false;
+        window()->display()->handleWindowDeactivated(m_window);
+    }
+
     if (!m_fullscreen && aboutToFullScreen) {
         if (!m_maximized)
             m_normalSize = m_window->window()->frameGeometry().size();
diff --git a/src/client/qwaylandxdgsurface_p.h b/src/client/qwaylandxdgsurface_p.h
index d4380d25f..e367980b7 100644
--- a/src/client/qwaylandxdgsurface_p.h
+++ b/src/client/qwaylandxdgsurface_p.h
@@ -106,6 +106,7 @@ private:
     bool m_maximized;
     bool m_minimized;
     bool m_fullscreen;
+    bool m_active;
     QSize m_normalSize;
     QMargins m_margins;
     QWaylandExtendedSurface *m_extendedWindow;