SVN commit 701053 by eros:

Faster background drawing. Speeds up a lot zooming operations and general compositing.


 M  +3 -1      libs/plasma/svg.cpp  
 M  +20 -2     plasma/plasma/desktopview.cpp  
 M  +7 -0      plasma/plasma/plasmaapp.cpp  


--- trunk/KDE/kdebase/workspace/libs/plasma/svg.cpp #701052:701053
@@ -135,7 +135,9 @@
                 renderer->render(&renderPainter, elementId);
             }
             renderPainter.end();
-            QPixmapCache::insert( id, p );
+            bool inserted = QPixmapCache::insert( id, p );
+            if (!inserted)
+                kDebug() << "pixmap cache is too small for inserting" << id << "of size" << s;
         }
 
         void createRenderer()
--- trunk/KDE/kdebase/workspace/plasma/plasma/desktopview.cpp #701052:701053
@@ -137,11 +137,29 @@
 
 void DesktopView::drawBackground(QPainter * painter, const QRectF & rect)
 {
+    // avoid expensive operations to the painter if there is nothing to paint
+    if (!m_background && !m_bitmapBackground)
+        return;
+
+    // draw the background untransformed (saves lots of per-pixel-math)
+    painter->save();
+    painter->resetTransform();
+    // blit the background (saves all the per-pixel-products that blending does)
+    painter->setCompositionMode(QPainter::CompositionMode_Source);
+
     if (m_background) {
-        m_background->paint(painter, rect);
+        // Plasma::Svg doesn't support drawing only part of the image (it only
+        // supports drawing the whole image to a rect), so we blit to 0,0-w,h
+        m_background->paint(painter, 0, 0);
     } else if (m_bitmapBackground) {
-        painter->drawPixmap(rect, *m_bitmapBackground, rect);
+        // for pixmaps we draw only the exposed part (untransformed since the
+        // bitmapBackground already has the size of the viewport)
+        QRect exposedRect = mapFromScene(rect).boundingRect();
+        painter->drawPixmap(exposedRect, *m_bitmapBackground, exposedRect);
     }
+
+    // restore transformation and composition mode
+    painter->restore();
 }
 
 void DesktopView::resizeEvent(QResizeEvent* event)
--- trunk/KDE/kdebase/workspace/plasma/plasma/plasmaapp.cpp #701052:701053
@@ -26,6 +26,7 @@
 #include "appadaptor.h"
 #include <unistd.h>
 
+#include <QPixmapCache>
 #include <QTimer>
 #include <QtDBus/QtDBus>
 
@@ -72,6 +73,12 @@
         setCrashHandler();
     }
 
+    // enlarge application pixmap cache (TODO: make this dependand on system
+    // memory and screen resolution. 8MB is ok for caching the background up
+    // to 1600x1200 resolution)
+    if (QPixmapCache::cacheLimit() < 8192)
+      QPixmapCache::setCacheLimit(8192);
+
     m_root = new RootWidget();
     m_root->setAsDesktop(KCmdLineArgs::parsedArgs()->isSet("desktop"));