Fixed holes in border image drawing by introducing new API.

When rasterizing two adjacent QRectFs it's important that the shared x
or y-edges have the exact same coordinates, or there might be a hole or
an overlapping pixel when they are rasterized. Since the
drawPixmapFragments API was based on a center position and a scale, it
can not be used for this purpose, as the in the situation of two
horizontally adjacent rectangles the right edge of the left-most rect
and the left edge of the right-most edge are computed differently. Thus
rounding errors can cause them to not be equal, especially when there's
also a scaling / translating painter transform involved.

Thus, to not sacrifice performance, we need to introduce a new
drawPixmapFragments API that's simply takes an array of target
rectangles and an array of source rectangles. It should give a slight
performance boost for the border pixmap use case as well, since there
are less floating point multiplications / divisions involved.

Task-number: QTBUG-19079
Reviewed-by: Kim

1 files changed, 2 insertions, 0 deletions

diff --git a/src/gui/painting/qpainter.h b/src/gui/painting/qpainter.h
index 30f8da0..12a14a2 100644
--- a/src/gui/painting/qpainter.h
+++ b/src/gui/painting/qpainter.h
@@ -380,6 +380,8 @@ public:
 
     void drawPixmapFragments(const PixmapFragment *fragments, int fragmentCount,
                              const QPixmap &pixmap, PixmapFragmentHints hints = 0);
+    void drawPixmapFragments(const QRectF *targetRects, const QRectF *sourceRects, int fragmentCount,
+                             const QPixmap &pixmap, PixmapFragmentHints hints = 0);
 
     void drawImage(const QRectF &targetRect, const QImage &image, const QRectF &sourceRect,
                    Qt::ImageConversionFlags flags = Qt::AutoColor);