Change timers to QElapsedTimers

Instead of calculating the elapsed time from epoch clock, using
a QElapsedTimer as well as reusing the timer object instead of
creating a new one in the scene each frame.

REVIEW: 102473

composite.cpp

@@ -168,7 +168,7 @@ void Workspace::setupCompositing()
     } else
         vBlankInterval = 1 << 10; // no sync - DO NOT set "0", would cause div-by-zero segfaults.
     vBlankPadding = 3; // vblank rounding errors... :-(
-    nextPaintReference = QDateTime::currentMSecsSinceEpoch();
+    nextPaintReference.restart();
     checkCompositeTimer();
     XCompositeRedirectSubwindows(display(), rootWindow(), CompositeRedirectManual);
     new EffectsHandlerImpl(scene->compositingType());   // sets also the 'effects' pointer
@@ -393,10 +393,10 @@ void Workspace::performCompositing()
     if (scene->waitSyncAvailable()) {
         // vsync: paint the scene, than rebase the timer and use the duration for next timeout estimation
         scene->paint(repaints, windows);
-        nextPaintReference = QDateTime::currentMSecsSinceEpoch();
+        nextPaintReference.restart();
     } else {
         // no vsyc -> inversion: reset the timer, then paint the scene, this way we can provide a constant framerate
-        nextPaintReference = QDateTime::currentMSecsSinceEpoch();
+        nextPaintReference.restart();
         scene->paint(repaints, windows);
     }
     // reset the roundin error corrective... :-(
@@ -436,7 +436,7 @@ void Workspace::setCompositeTimer()
         return;
 
     // interval - "time since last paint completion" - "time we need to paint"
-    uint passed = (QDateTime::currentMSecsSinceEpoch() - nextPaintReference) << 10;
+    uint passed = nextPaintReference.elapsed() << 10;
     uint delay = fpsInterval;
     if (scene->waitSyncAvailable()) {
         if (passed > fpsInterval) {

scene.cpp

@@ -164,7 +164,7 @@ void Scene::paintScreen(int* mask, QRegion* region)
 // Compute time since the last painting pass.
 void Scene::updateTimeDiff()
 {
-    if (last_time.isNull()) {
+    if (!last_time.isValid()) {
         // Painting has been idle (optimized out) for some time,
         // which means time_diff would be huge and would break animations.
         // Simply set it to one (zero would mean no change at all and could
@@ -174,14 +174,14 @@ void Scene::updateTimeDiff()
         time_diff = last_time.elapsed();
     if (time_diff < 0)   // check time rollback
         time_diff = 1;
-    last_time.start();;
+    last_time.restart();;
 }
 
 // Painting pass is optimized away.
 void Scene::idle()
 {
     // Don't break time since last paint for the next pass.
-    last_time = QTime();
+    last_time.invalidate();;
 }
 
 // the function that'll be eventually called by paintScreen() above

scene.h

@@ -21,8 +21,6 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #ifndef KWIN_SCENE_H
 #define KWIN_SCENE_H
 
-#include <QDateTime>
-
 #include "toplevel.h"
 #include "utils.h"
 #include "kwineffects.h"
@@ -151,11 +149,12 @@ protected:
     // time since last repaint
     int time_diff;
     uint lastRenderTime;
-    QTime last_time;
+    QElapsedTimer last_time;
     Workspace* wspace;
     bool has_waitSync;
     LanczosFilter* lanczos_filter;
     OverlayWindow* m_overlayWindow;
+    QElapsedTimer m_renderTimer;
 };
 
 // The base class for windows representations in composite backends

scene_opengl_egl.cpp

@@ -167,7 +167,7 @@ bool SceneOpenGL::initDrawableConfigs()
 // the entry function for painting
 void SceneOpenGL::paint(QRegion damage, ToplevelList toplevels)
 {
-    QTime t = QTime::currentTime();
+    m_renderTimer.restart();
     foreach (Toplevel * c, toplevels) {
         assert(windows.contains(c));
         stacking_order.append(windows[ c ]);
@@ -179,7 +179,8 @@ void SceneOpenGL::paint(QRegion damage, ToplevelList toplevels)
     ungrabXServer(); // ungrab before flushBuffer(), it may wait for vsync
     if (m_overlayWindow->window())  // show the window only after the first pass, since
         m_overlayWindow->show();   // that pass may take long
-    lastRenderTime = t.elapsed();
+    lastRenderTime = m_renderTimer.elapsed();
+    m_renderTimer.invalidate();
     flushBuffer(mask, damage);
     // do cleanup
     stacking_order.clear();

scene_opengl_glx.cpp

@@ -437,7 +437,7 @@ bool SceneOpenGL::initDrawableConfigs()
 // the entry function for painting
 void SceneOpenGL::paint(QRegion damage, ToplevelList toplevels)
 {
-    QTime t = QTime::currentTime();
+    m_renderTimer.restart();
     foreach (Toplevel * c, toplevels) {
         assert(windows.contains(c));
         stacking_order.append(windows[ c ]);
@@ -457,7 +457,8 @@ void SceneOpenGL::paint(QRegion damage, ToplevelList toplevels)
     ungrabXServer(); // ungrab before flushBuffer(), it may wait for vsync
     if (m_overlayWindow->window())  // show the window only after the first pass, since
         m_overlayWindow->show();   // that pass may take long
-    lastRenderTime = t.elapsed();
+    lastRenderTime = m_renderTimer.elapsed();
+    m_renderTimer.invalidate();
     flushBuffer(mask, damage);
     // do cleanup
     stacking_order.clear();

scene_xrender.cpp

@@ -161,7 +161,7 @@ void SceneXrender::createBuffer()
 // the entry point for painting
 void SceneXrender::paint(QRegion damage, ToplevelList toplevels)
 {
-    QTime t = QTime::currentTime();
+    m_renderTimer.restart();
     foreach (Toplevel * c, toplevels) {
         assert(windows.contains(c));
         stacking_order.append(windows[ c ]);
@@ -170,7 +170,8 @@ void SceneXrender::paint(QRegion damage, ToplevelList toplevels)
     paintScreen(&mask, &damage);
     if (m_overlayWindow->window())  // show the window only after the first pass, since
         m_overlayWindow->show();   // that pass may take long
-    lastRenderTime = t.elapsed();
+    lastRenderTime = m_renderTimer.elapsed();
+    m_renderTimer.invalidate();
     flushBuffer(mask, damage);
     // do cleanup
     stacking_order.clear();

workspace.h

@@ -29,7 +29,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QCursor>
 #include <netwm.h>
 #include <kxmessages.h>
-#include <QDateTime>
+#include <QElapsedTimer>
 #include <kmanagerselection.h>
 
 #include "kactivitycontroller.h"
@@ -888,7 +888,7 @@ private:
     KSelectionOwner* cm_selection;
     bool compositingSuspended, compositingBlocked;
     QBasicTimer compositeTimer;
-    qint64 nextPaintReference;
+    QElapsedTimer nextPaintReference;
     QTimer mousePollingTimer;
     uint vBlankInterval, vBlankPadding, fpsInterval, estimatedRenderTime;
     int xrrRefreshRate; // used only for compositing