Effects Hook to paint a desktop

A specialised paintScreen method to render all windows of one
desktop. It's intended to be called during an already started
paintScreen process to get e.g. a thumbnail of a desktop.

Currently not yet exported to the Effects.

effects.cpp

@@ -215,6 +215,8 @@ EffectsHandlerImpl::EffectsHandlerImpl(Compositor *compositor, Scene *scene)
     , m_compositor(compositor)
     , m_scene(scene)
     , m_screenLockerWatcher(new ScreenLockerWatcher(this))
+    , m_desktopRendering(false)
+    , m_currentRenderedDesktop(0)
 {
     new EffectsAdaptor(this);
     QDBusConnection dbus = QDBusConnection::sessionBus();
@@ -373,6 +375,22 @@ void EffectsHandlerImpl::paintScreen(int mask, QRegion region, ScreenPaintData&
         m_scene->finalPaintScreen(mask, region, data);
 }
 
+void EffectsHandlerImpl::paintDesktop(int desktop, int mask, QRegion region, ScreenPaintData &data)
+{
+    if (desktop < 1 || desktop > numberOfDesktops()) {
+        return;
+    }
+    m_currentRenderedDesktop = desktop;
+    m_desktopRendering = true;
+    // save the paint screen iterator
+    QList<Effect*>::iterator savedIterator = m_currentPaintScreenIterator;
+    m_currentPaintScreenIterator = m_activeEffects.begin();
+    effects->paintScreen(mask, region, data);
+    // restore the saved iterator
+    m_currentPaintScreenIterator = savedIterator;
+    m_desktopRendering = false;
+}
+
 void EffectsHandlerImpl::postPaintScreen()
 {
     if (m_currentPaintScreenIterator != m_activeEffects.end()) {

effects.h

@@ -61,6 +61,10 @@ public:
     virtual ~EffectsHandlerImpl();
     virtual void prePaintScreen(ScreenPrePaintData& data, int time);
     virtual void paintScreen(int mask, QRegion region, ScreenPaintData& data);
+    /**
+     * Special hook to perform a paintScreen but just with the windows on @p desktop.
+     **/
+    void paintDesktop(int desktop, int mask, QRegion region, ScreenPaintData& data);
     virtual void postPaintScreen();
     virtual void prePaintWindow(EffectWindow* w, WindowPrePaintData& data, int time);
     virtual void paintWindow(EffectWindow* w, int mask, QRegion region, WindowPaintData& data);
@@ -180,6 +184,19 @@ public:
     QList<EffectWindow*> elevatedWindows() const;
     QStringList activeEffects() const;
 
+    /**
+     * @returns Whether we are currently in a desktop rendering process triggered by paintDesktop hook
+     **/
+    bool isDesktopRendering() const {
+        return m_desktopRendering;
+    }
+    /**
+     * @returns the desktop currently being rendered in the paintDesktop hook.
+     **/
+    int currentRenderedDesktop() const {
+        return m_currentRenderedDesktop;
+    }
+
 public Q_SLOTS:
     void slotCurrentTabAboutToChange(EffectWindow* from, EffectWindow* to);
     void slotTabAdded(EffectWindow* from, EffectWindow* to);
@@ -248,6 +265,8 @@ private:
     Scene *m_scene;
     QList< InputWindowPair > input_windows;
     ScreenLockerWatcher *m_screenLockerWatcher;
+    bool m_desktopRendering;
+    int m_currentRenderedDesktop;
 };
 
 class EffectWindowImpl : public EffectWindow

scene.cpp

@@ -589,8 +589,14 @@ void Scene::Window::resetPaintingEnabled()
     disable_painting = 0;
     if (toplevel->isDeleted())
         disable_painting |= PAINT_DISABLED_BY_DELETE;
-    if (!toplevel->isOnCurrentDesktop())
+    if (static_cast<EffectsHandlerImpl*>(effects)->isDesktopRendering()) {
-        disable_painting |= PAINT_DISABLED_BY_DESKTOP;
+        if (!toplevel->isOnDesktop(static_cast<EffectsHandlerImpl*>(effects)->currentRenderedDesktop())) {
+            disable_painting |= PAINT_DISABLED_BY_DESKTOP;
+        }
+    } else {
+        if (!toplevel->isOnCurrentDesktop())
+            disable_painting |= PAINT_DISABLED_BY_DESKTOP;
+    }
     if (!toplevel->isOnCurrentActivity())
         disable_painting |= PAINT_DISABLED_BY_ACTIVITY;
     if (toplevel->isClient()) {