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Optimize AlphaBlt() to reset the minimal amount of pixels

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Modify the loop fixing alpha channel value in order to increase speed when
ARGB bitmap is drawn on 0RGB DIB bitmap or 32-bit DDB bitmap.

Closes #16766.
This commit is contained in:
Artur Wieczorek
2015-12-06 13:17:47 +01:00
committed by Vadim Zeitlin
parent 530276ec6a
commit c239160d33
1 changed files with 11 additions and 3 deletions
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14
src/msw/dc.cpp
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@@ -2620,15 +2620,23 @@ static bool AlphaBlt(wxMSWDCImpl* dcDst,
// Notice the extra block: we must destroy wxAlphaPixelData
// before selecting the bitmap into the DC again.
{
// Since drawn bitmap can only partially overlap
// with destination bitmap we need to calculate
// efective drawing area location.
const wxRect rectDst(bmpOld.GetSize());
const wxRect rectDrawn(x, y, dstWidth, dstHeight);
const wxRect r = rectDrawn.Intersect(rectDst);
wxAlphaPixelData data(bmpOld);
if ( data )
{
wxAlphaPixelData::Iterator p(data);
for ( int old_y = 0; old_y < data.GetHeight(); old_y++ )
p.Offset(data, r.GetLeft(), r.GetTop());
for ( int old_y = 0; old_y < r.GetHeight(); old_y++ )
{
wxAlphaPixelData::Iterator rowStart = p;
for ( int old_x = 0; old_x < data.GetWidth(); old_x++ )
for ( int old_x = 0; old_x < r.GetWidth(); old_x++ )
{
// We choose to use wxALPHA_TRANSPARENT instead
// of perhaps more logical wxALPHA_OPAQUE here