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Commit de25a672 authored by Chris Craik's avatar Chris Craik
Browse files

Saturate alpha values when overlaying glyphs 

bug:19062769

Glyphs were stored to the output buffer with the assumption of
non-overlap, which is incorrect for certain fonts/strings. Instead,
blend src into dst, so new glyphs don't clobber existing content.

Change-Id: I6e22037500e67d5348ee2a43d939416c23c4d1ea
parent 82b3f677

libs/hwui/font/Font.cpp

+7 −7
Original line number Diff line number Diff line
@@ -228,15 +228,15 @@ void Font::drawCachedGlyphBitmap(CachedGlyphInfo* glyph, int x, int y, uint8_t* 
    for (uint32_t cacheY = startY, bitmapY = dstY * bitmapWidth; cacheY < endY;

            cacheY += srcStride, bitmapY += bitmapWidth) {



        if (formatSize == 1) {

            memcpy(&bitmap[bitmapY + dstX], &cacheBuffer[cacheY + glyph->mStartX], glyph->mBitmapWidth);

        } else {

        for (uint32_t i = 0; i < glyph->mBitmapWidth; ++i) {

                bitmap[bitmapY + dstX + i] = cacheBuffer[cacheY + (glyph->mStartX + i)*formatSize + alpha_channel_offset];

            }

            uint8_t* dst = &(bitmap[bitmapY + dstX + i]);

            const uint8_t& src = cacheBuffer[

                    cacheY + (glyph->mStartX + i)*formatSize + alpha_channel_offset];

            // Add alpha values to a max of 255, full opacity. This is done to handle

            // fonts/strings where glyphs overlap.

            *dst = std::min(*dst + src, 255);

        }

    }



}



void Font::drawCachedGlyph(CachedGlyphInfo* glyph, float x, float hOffset, float vOffset,