Perform compositing even if there is nothing to repaint

In rare cases, the Compositor has to perform a compositing if there is
nothing to repaint. For example, if a client has committed a frame
callback to get notified about the next vblank event without damaging
the surface.

composite.cpp

@@ -649,17 +649,6 @@ void Compositor::performCompositing()
         win->getDamageRegionReply();
     }
 
-    if (repaints_region.isEmpty() && !windowRepaintsPending()) {
-        m_scene->idle();
-        m_timeSinceLastVBlank = fpsInterval - (options->vBlankTime() + 1); // means "start now"
-        // Note: It would seem here we should undo suspended unredirect, but when scenes need
-        // it for some reason, e.g. transformations or translucency, the next pass that does not
-        // need this anymore and paints normally will also reset the suspended unredirect.
-        // Otherwise the window would not be painted normally anyway.
-        compositeTimer.stop();
-        return;
-    }
-
     // Skip windows that are not yet ready for being painted and if screen is locked skip windows
     // that are neither lockscreen nor inputmethod windows.
     //
@@ -735,43 +724,6 @@ void Compositor::performCompositing()
     }
 }
 
-template <class T>
-static bool repaintsPending(const QList<T*> &windows)
-{
-    return std::any_of(windows.begin(), windows.end(),
-                       [](const T *t) { return t->wantsRepaint(); });
-}
-
-bool Compositor::windowRepaintsPending() const
-{
-    if (repaintsPending(Workspace::self()->clientList())) {
-        return true;
-    }
-    if (repaintsPending(Workspace::self()->unmanagedList())) {
-        return true;
-    }
-    if (repaintsPending(Workspace::self()->deletedList())) {
-        return true;
-    }
-    if (auto *server = waylandServer()) {
-        const auto &clients = server->clients();
-        auto test = [](const AbstractClient *c) {
-            return c->readyForPainting() && c->wantsRepaint();
-        };
-        if (std::any_of(clients.begin(), clients.end(), test)) {
-            return true;
-        }
-    }
-    const auto &internalClients = workspace()->internalClients();
-    auto internalTest = [] (const InternalClient *client) {
-        return client->isShown(true) && client->wantsRepaint();
-    };
-    if (std::any_of(internalClients.begin(), internalClients.end(), internalTest)) {
-        return true;
-    }
-    return false;
-}
-
 void Compositor::setCompositeTimer()
 {
     if (m_state != State::On) {

composite.h

@@ -134,7 +134,6 @@ private:
     void cleanupX11();
 
     void setCompositeTimer();
-    bool windowRepaintsPending() const;
 
     void releaseCompositorSelection();
     void deleteUnusedSupportProperties();

scene.cpp

@@ -1173,17 +1173,6 @@ void Scene::Window::reallocRepaints()
     m_layerRepaints.fill(infiniteRegion());
 }
 
-static bool wantsRepaint_test(const QRegion &region)
-{
-    return !region.isEmpty();
-}
-
-bool Scene::Window::wantsRepaint() const
-{
-    return std::any_of(m_repaints.begin(), m_repaints.end(), wantsRepaint_test) ||
-            std::any_of(m_layerRepaints.begin(), m_layerRepaints.end(), wantsRepaint_test);
-}
-
 //****************************************
 // WindowPixmap
 //****************************************

scene.h

@@ -358,7 +358,6 @@ public:
     void addLayerRepaint(const QRegion &region);
     QRegion repaints(int screen) const;
     void resetRepaints(int screen);
-    bool wantsRepaint() const;
 
     virtual QSharedPointer<GLTexture> windowTexture() {
         return {};

toplevel.cpp

@@ -489,14 +489,6 @@ void Toplevel::addWorkspaceRepaint(const QRegion &region)
     }
 }
 
-bool Toplevel::wantsRepaint() const
-{
-    if (!effectWindow() || !effectWindow()->sceneWindow()) {
-        return false;
-    }
-    return effectWindow()->sceneWindow()->wantsRepaint();
-}
-
 void Toplevel::setReadyForPainting()
 {
     if (!ready_for_painting) {

toplevel.h

@@ -463,7 +463,6 @@ public:
     void addWorkspaceRepaint(const QRect& r);
     void addWorkspaceRepaint(int x, int y, int w, int h);
     void addWorkspaceRepaint(const QRegion &region);
-    bool wantsRepaint() const;
     QRegion damage() const;
     void resetDamage();
     EffectWindowImpl* effectWindow();