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, 11 insertions, 3 deletions

diff --git a/src/gui/image/qpixmap_raster.cpp b/src/gui/image/qpixmap_raster.cpp
index 2c57eded94..9cc896b473 100644
--- a/src/gui/image/qpixmap_raster.cpp
+++ b/src/gui/image/qpixmap_raster.cpp
@@ -85,6 +85,10 @@ void QRasterPixmapData::resize(int width, int height)
 #endif
 
     image = QImage(width, height, format);
+    w = width;
+    h = height;
+    d = image.depth();
+    is_null = (w <= 0 || h <= 0);
 
     if (pixelType() == BitmapType && !image.isNull()) {
         image.setNumColors(2);
@@ -168,6 +172,10 @@ void QRasterPixmapData::fromImage(const QImage &sourceImage,
         }
     }
 #endif
+    w = image.d->width;
+    h = image.d->height;
+    d = image.d->depth;
+    is_null = (w <= 0 || h <= 0);
 
     setSerialNumber(image.serialNumber());
 }
@@ -329,9 +337,9 @@ int QRasterPixmapData::metric(QPaintDevice::PaintDeviceMetric metric) const
     // override the image dpi with the screen dpi when rendering to a pixmap
     switch (metric) {
     case QPaintDevice::PdmWidth:
-        return d->width;
+        return w;
     case QPaintDevice::PdmHeight:
-        return d->height;
+        return h;
     case QPaintDevice::PdmWidthMM:
         return qRound(d->width * 25.4 / qt_defaultDpiX());
     case QPaintDevice::PdmHeightMM:
@@ -339,7 +347,7 @@ int QRasterPixmapData::metric(QPaintDevice::PaintDeviceMetric metric) const
     case QPaintDevice::PdmNumColors:
         return d->colortable.size();
     case QPaintDevice::PdmDepth:
-        return d->depth;
+        return this->d;
     case QPaintDevice::PdmDpiX: // fall-through
     case QPaintDevice::PdmPhysicalDpiX:
         return qt_defaultDpiX();