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Commit e324197e authored by Romain Guy's avatar Romain Guy
Browse files

DO NOT MERGE Correctly implement the CLEAR xfermode. 

This bug is a regression from the software pipeline and prevents
applications from implementing an "eraser" type tool (for instance
a drawing/painting apps.) This issue affects external applications
when they turn on hardware acceleration.

The previous implementation was using glBlendFunc with the parameters
GL_ZERO/GL_ZERO which doesn't work for text, paths and other alpha
sources (anti-aliasing.) The correct implementation is GL_ZERO/
GL_ONE_MINUS_SRC_ALPHA.

Change-Id: I1446e83480e46174b880120069d76fcad14ba300
parent 27ac64ec

libs/hwui/OpenGLRenderer.cpp

+2 −2
Original line number Diff line number Diff line
@@ -63,7 +63,7 @@ struct Blender { 
// In this array, the index of each Blender equals the value of the first

// entry. For instance, gBlends[1] == gBlends[SkXfermode::kSrc_Mode]

static const Blender gBlends[] = {

    { SkXfermode::kClear_Mode,   GL_ZERO,                 GL_ZERO },

    { SkXfermode::kClear_Mode,   GL_ZERO,                 GL_ONE_MINUS_SRC_ALPHA },

    { SkXfermode::kSrc_Mode,     GL_ONE,                  GL_ZERO },

    { SkXfermode::kDst_Mode,     GL_ZERO,                 GL_ONE },

    { SkXfermode::kSrcOver_Mode, GL_ONE,                  GL_ONE_MINUS_SRC_ALPHA },
@@ -81,7 +81,7 @@ static const Blender gBlends[] = { 
// this array's SrcOver blending mode is actually DstOver. You can refer to

// createLayer() for more information on the purpose of this array.

static const Blender gBlendsSwap[] = {

    { SkXfermode::kClear_Mode,   GL_ZERO,                 GL_ZERO },

    { SkXfermode::kClear_Mode,   GL_ONE_MINUS_DST_ALPHA,  GL_ZERO },

    { SkXfermode::kSrc_Mode,     GL_ZERO,                 GL_ONE },

    { SkXfermode::kDst_Mode,     GL_ONE,                  GL_ZERO },

    { SkXfermode::kSrcOver_Mode, GL_ONE_MINUS_DST_ALPHA,  GL_ONE },