Speed up QPixmap::width(), height(), isNull() and depth().

This change moves the w, h, d variables to QPixmapData and introduces
is_null to keep track of nullness. This is possible only because
QPixmapData is internal API; otherwise we'd have to be smarter.

The optimization makes the QPixmap::width() function take 7 instructions,
down from 34 before. For the calculator demo in the declarative ui branch
this reduces a block of 750000 instructions (out of 30000000) to around
100000-150000 instructions.

Tested on Windows, Linux, Mac. Raster, X11 and OpenGL paint engines. Have
not tested the DirectFB engine.

Reviewed-by: Trond

1 files changed, 9 insertions, 4 deletions

diff --git a/src/gui/image/qpixmapdata_p.h b/src/gui/image/qpixmapdata_p.h
index 4c49dd2..29dafaf 100644
--- a/src/gui/image/qpixmapdata_p.h
+++ b/src/gui/image/qpixmapdata_p.h
@@ -99,13 +99,18 @@ public:
 
     virtual QImage* buffer();
 
-    int width() const { return metric(QPaintDevice::PdmWidth); }
-    int height() const { return metric(QPaintDevice::PdmHeight); }
-    int numColors() const { return metric(QPaintDevice::PdmNumColors); }
-    int depth() const { return metric(QPaintDevice::PdmDepth); }
+    inline int width() const { return w; }
+    inline int height() const { return h; }
+    inline int numColors() const { return metric(QPaintDevice::PdmNumColors); }
+    inline int depth() const { return d; }
+    inline bool isNull() const { return is_null; }
 
 protected:
     void setSerialNumber(int serNo);
+    int w;
+    int h;
+    int d;
+    bool is_null;
 
 private:
     friend class QPixmap;