Fixed antialiased rasterization bug in raster engine.

When rasterization in the gray raster fails due to out of memory there
might already have been a number of spans flushed. To avoid flushing
these spans multiple times and thus getting overdraw artifacts we need
to keep track of how many spans to skip when we redo the rasterization.

This fixes the rendering error in arthur test paths_aa.qps

Reviewed-by: Yoann Lopes

1 files changed, 9 insertions, 0 deletions

diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp
index 09a87aa..36e1082 100644
--- a/src/gui/painting/qpaintengine_raster.cpp
+++ b/src/gui/painting/qpaintengine_raster.cpp
@@ -4148,6 +4148,10 @@ void QRasterPaintEnginePrivate::rasterize(QT_FT_Outline *outline,
     rasterize(outline, callback, (void *)spanData, rasterBuffer);
 }
 
+extern "C" {
+    int q_gray_rendered_spans(QT_FT_Raster raster);
+}
+
 void QRasterPaintEnginePrivate::rasterize(QT_FT_Outline *outline,
                                           ProcessSpans callback,
                                           void *userData, QRasterBuffer *)
@@ -4212,10 +4216,13 @@ void QRasterPaintEnginePrivate::rasterize(QT_FT_Outline *outline,
     bool done = false;
     int error;
 
+    int rendered_spans = 0;
+
     while (!done) {
 
         rasterParams.flags |= (QT_FT_RASTER_FLAG_AA | QT_FT_RASTER_FLAG_DIRECT);
         rasterParams.gray_spans = callback;
+        rasterParams.skip_spans = rendered_spans;
         error = qt_ft_grays_raster.raster_render(*grayRaster.data(), &rasterParams);
 
         // Out of memory, reallocate some more and try again...
@@ -4244,6 +4251,8 @@ void QRasterPaintEnginePrivate::rasterize(QT_FT_Outline *outline,
 #endif
             Q_CHECK_PTR(rasterPoolBase); // note: we just freed the old rasterPoolBase. I hope it's not fatal.
 
+            rendered_spans += q_gray_rendered_spans(*grayRaster.data());
+
             qt_ft_grays_raster.raster_done(*grayRaster.data());
             qt_ft_grays_raster.raster_new(grayRaster.data());
             qt_ft_grays_raster.raster_reset(*grayRaster.data(), rasterPoolBase, rasterPoolSize);