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

1 files changed, 6 insertions, 1 deletions

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