allow for a limited number of updates on transitioning windowspastdamages

Repair transitioning windows not more than ten times per second.
Only implemented in the EGL variant.

 * src/mcompositewindow.h
 * src/mtexturepixmapitem.h:
   Add an optional Time parameter to MCompositeWindow::updateWindowPixmap()
   denoting the time when the damage notification was sent by the server.
 * src/mtexturepixmapitem.h:
 * src/mtexturepixmapitem_p.cpp:
   Add MTexturePixmapPrivate::pastDamages to remember them for the timeframe
   if necessary.
 * src/mtexturepixmapitem_egl.cpp (MTexturePixmapItem::updateWindowPixmap::updateWindowPixmap):
   If we receive a damage during a transition check if we can afford a repair
   an do it if all's positive.
 * src/mtexturepixmapitem_glx.cpp (MTexturePixmapItem::updateWindowPixmap::updateWindowPixmap)
   Just added the new parameter, but left unused.

7 files changed, 45 insertions, 7 deletions

diff --git a/src/mcompositemanager.cpp b/src/mcompositemanager.cpp
index 9b81c54..82a2b9c 100644
--- a/src/mcompositemanager.cpp
+++ b/src/mcompositemanager.cpp
@@ -910,7 +910,7 @@ void MCompositeManagerPrivate::damageEvent(XDamageNotifyEvent *e)
 
     MCompositeWindow *item = COMPOSITE_WINDOW(e->drawable);
     if (item && rects) {
-        item->updateWindowPixmap(rects, num);
+        item->updateWindowPixmap(rects, num, e->timestamp);
         if (item->waitingForDamage())
             item->damageReceived(false);
     }
diff --git a/src/mcompositewindow.h b/src/mcompositewindow.h
index 5d53b88..b82dfc6 100644
--- a/src/mcompositewindow.h
+++ b/src/mcompositewindow.h
@@ -239,7 +239,8 @@ public:
      * Ensures that the corresponding texture reflects the contents of the
      * associated pixmap and schedules a redraw of this item.
      */
-    virtual void updateWindowPixmap(XRectangle *rects = 0, int num = 0) = 0;
+    virtual void updateWindowPixmap(XRectangle *rects = 0, int num = 0,
+                                    Time when = 0) = 0;
 
     /*!
      * Recreates the pixmap id and saves the offscreen buffer that represents
diff --git a/src/mtexturepixmapitem.h b/src/mtexturepixmapitem.h
index 1a25b29..15ee6b2 100644
--- a/src/mtexturepixmapitem.h
+++ b/src/mtexturepixmapitem.h
@@ -61,7 +61,8 @@ public:
      * Ensures that the corresponding texture reflects the contents of the
      * associated pixmap and schedules a redraw of this item.
      */
-    void updateWindowPixmap(XRectangle *rects = 0, int num = 0);
+    void updateWindowPixmap(XRectangle *rects = 0, int num = 0,
+                            Time when = 0);
 
     /*!
      * Recreates the pixmap id and saves the offscreen buffer that represents
diff --git a/src/mtexturepixmapitem_egl.cpp b/src/mtexturepixmapitem_egl.cpp
index c5487e7..b60a28b 100644
--- a/src/mtexturepixmapitem_egl.cpp
+++ b/src/mtexturepixmapitem_egl.cpp
@@ -251,9 +251,38 @@ void MTexturePixmapItem::cleanup()
     XFreePixmap(QX11Info::display(), d->windowp);
 }
 
-void MTexturePixmapItem::updateWindowPixmap(XRectangle *rects, int num)
+void MTexturePixmapItem::updateWindowPixmap(XRectangle *rects, int num,
+                                            Time when)
 {
-    if (hasTransitioningWindow() || d->direct_fb_render || !windowVisible()
+    // When a window is in transitioning limit the number of updates
+    // to @limit/@expiry miliseconds.
+    const unsigned expiry = 1000;
+    const int      limit  =   10;
+
+    if (hasTransitioningWindow()) {
+        // Limit the number of damages we're willing to process if we're
+        // in the middle of a transition, so the competition for the GL
+        // resources will be less tight.
+        if (d->pastDamages) {
+            // Forget about pastDamages we received long ago.
+            while (d->pastDamages->size() > 0
+                   && d->pastDamages->first() + expiry < when)
+                d->pastDamages->removeFirst();
+            if (d->pastDamages->size() >= limit)
+                // Too many damages in the given timeframe, throttle.
+                return;
+        } else
+            d->pastDamages = new QList<Time>;
+        // Can afford this damage, but recoed when we received it,
+        // so to know when to forget about them.
+        d->pastDamages->append(when);
+    } else if (d->pastDamages) {
+        // The window is not transitioning, forget about all pastDamages.
+        delete d->pastDamages;
+        d->pastDamages = NULL;
+    }
+
+    if (d->direct_fb_render || !windowVisible()
         || propertyCache()->isInputOnly())
         return;
 
diff --git a/src/mtexturepixmapitem_glx.cpp b/src/mtexturepixmapitem_glx.cpp
index 0129a31..c2551a5 100644
--- a/src/mtexturepixmapitem_glx.cpp
+++ b/src/mtexturepixmapitem_glx.cpp
@@ -273,7 +273,8 @@ void MTexturePixmapItem::cleanup()
         XFreePixmap(QX11Info::display(), d->windowp);
 }
 
-void MTexturePixmapItem::updateWindowPixmap(XRectangle *rects, int num)
+void MTexturePixmapItem::updateWindowPixmap(XRectangle *rects, int num,
+                                            Time when)
 {
     Q_UNUSED(rects);
     Q_UNUSED(num);
diff --git a/src/mtexturepixmapitem_p.cpp b/src/mtexturepixmapitem_p.cpp
index e8a1e98..33a9da4 100644
--- a/src/mtexturepixmapitem_p.cpp
+++ b/src/mtexturepixmapitem_p.cpp
@@ -412,7 +412,8 @@ MTexturePixmapPrivate::MTexturePixmapPrivate(Qt::HANDLE window,
       direct_fb_render(false),
       angle(0),
       item(p),
-      prev_effect(0)
+      prev_effect(0),
+      pastDamages(0)
 {
     XCompositeRedirectWindow(QX11Info::display(), window,
                              CompositeRedirectManual);
diff --git a/src/mtexturepixmapitem_p.h b/src/mtexturepixmapitem_p.h
index c351b00..cd4c086 100644
--- a/src/mtexturepixmapitem_p.h
+++ b/src/mtexturepixmapitem_p.h
@@ -89,6 +89,11 @@ public:
     QPointer<MCompositeWindowShaderEffect> current_effect;
     const MCompositeWindowShaderEffect *prev_effect;
 
+    // Contains a limited number of server times we received damage
+    // notifications for this window.  Only used by the EGL variant
+    // to throttle repairs if the window is transitioning.
+    QList<Time> *pastDamages;
+
 #ifdef GLES2_VERSION
     static EglResourceManager *eglresource;
 #endif