Reduce overhead of paint engine-specific pixmap filters

Engine-specific pixmap filters were being created, used, and destroyed
every time draw() was called on QPixmapColorizeFilter, QPixmapBlurFilter,
and so on.  This had a heavy performance penalty and made it difficult
for the GL paint engine to cache shaders from one request to the next.

A generic filter can request an engine-specific filter that matches its
parameters.  The engine can either create a new one or return a previously
allocated filter object.

Ownership of engine-specific pixmap filter objects is moved to the
paint engine itself.

Reviewed-by: Andrew den Exter
Reviewed-by: Michael Brasser
Reviewed-by: Michael Goddard
Reviewed-by: Sarah Smith

2 files changed, 9 insertions, 7 deletions

diff --git a/src/gui/image/qpixmapfilter.cpp b/src/gui/image/qpixmapfilter.cpp
index 4fa2e6c..4fb650f 100644
--- a/src/gui/image/qpixmapfilter.cpp
+++ b/src/gui/image/qpixmapfilter.cpp
@@ -418,13 +418,12 @@ void QPixmapConvolutionFilter::draw(QPainter *painter, const QPointF &p, const Q
         return;
 
     QPixmapFilter *filter = painter->paintEngine() && painter->paintEngine()->isExtended() ?
-        static_cast<QPaintEngineEx *>(painter->paintEngine())->createPixmapFilter(type()) : 0;
+        static_cast<QPaintEngineEx *>(painter->paintEngine())->pixmapFilter(type(), this) : 0;
     QPixmapConvolutionFilter *convolutionFilter = static_cast<QPixmapConvolutionFilter*>(filter);
     if (convolutionFilter) {
         convolutionFilter->setConvolutionKernel(d->convolutionKernel, d->kernelWidth, d->kernelHeight);
         convolutionFilter->d_func()->convoluteAlpha = d->convoluteAlpha;
         convolutionFilter->draw(painter, p, src, srcRect);
-        delete convolutionFilter;
         return;
     }
 
@@ -669,13 +668,12 @@ void QPixmapBlurFilter::draw(QPainter *painter, const QPointF &p, const QPixmap
     }
 
     QPixmapFilter *filter = painter->paintEngine() && painter->paintEngine()->isExtended() ?
-        static_cast<QPaintEngineEx *>(painter->paintEngine())->createPixmapFilter(type()) : 0;
+        static_cast<QPaintEngineEx *>(painter->paintEngine())->pixmapFilter(type(), this) : 0;
     QPixmapBlurFilter *blurFilter = static_cast<QPixmapBlurFilter*>(filter);
     if (blurFilter) {
         blurFilter->setRadius(d->radius);
         blurFilter->setQuality(d->quality);
         blurFilter->draw(painter, p, src, srcRect);
-        delete blurFilter;
         return;
     }
 
@@ -836,13 +834,12 @@ void QPixmapColorizeFilter::draw(QPainter *painter, const QPointF &dest, const Q
 {
     Q_D(const QPixmapColorizeFilter);
     QPixmapFilter *filter = painter->paintEngine() && painter->paintEngine()->isExtended() ?
-        static_cast<QPaintEngineEx *>(painter->paintEngine())->createPixmapFilter(type()) : 0;
+        static_cast<QPaintEngineEx *>(painter->paintEngine())->pixmapFilter(type(), this) : 0;
     QPixmapColorizeFilter *colorizeFilter = static_cast<QPixmapColorizeFilter*>(filter);
     if (colorizeFilter) {
         colorizeFilter->setColor(d->color);
         colorizeFilter->setStrength(d->strength);
         colorizeFilter->draw(painter, dest, src, srcRect);
-        delete colorizeFilter;
         return;
     }
 
diff --git a/src/gui/painting/qpaintengineex_p.h b/src/gui/painting/qpaintengineex_p.h
index 9f0d84a..a12a71f 100644
--- a/src/gui/painting/qpaintengineex_p.h
+++ b/src/gui/painting/qpaintengineex_p.h
@@ -207,7 +207,12 @@ public:
     virtual void beginNativePainting() {}
     virtual void endNativePainting() {}
 
-    virtual QPixmapFilter *createPixmapFilter(int /*type*/) const { return 0; }
+    // Return a pixmap filter of "type" that can render the parameters
+    // in "prototype".  The returned filter is owned by the engine and
+    // will be destroyed when the engine is destroyed.  The "prototype"
+    // allows the engine to pick different filters based on the parameters
+    // that will be requested, and not just the "type".
+    virtual QPixmapFilter *pixmapFilter(int /*type*/, const QPixmapFilter * /*prototype*/) { return 0; }
 
     // These flags are needed in the implementation of paint buffers.
     enum Flags