SkShader::Context* SkComposeShader::onCreateContext(const ContextRec& rec, void* storage) const {
char* aStorage = (char*) storage + sizeof(ComposeShaderContext);
char* bStorage = aStorage + fShaderA->contextSize(rec);
// we preconcat our localMatrix (if any) with the device matrix
// before calling our sub-shaders
SkMatrix tmpM;
tmpM.setConcat(*rec.fMatrix, this->getLocalMatrix());
// Our sub-shaders need to see opaque, so by combining them we don't double-alphatize the
// result. ComposeShader itself will respect the alpha, and post-apply it after calling the
// sub-shaders.
SkPaint opaquePaint(*rec.fPaint);
opaquePaint.setAlpha(0xFF);
ContextRec newRec(rec);
newRec.fMatrix = &tmpM;
newRec.fPaint = &opaquePaint;
SkShader::Context* contextA = fShaderA->createContext(newRec, aStorage);
SkShader::Context* contextB = fShaderB->createContext(newRec, bStorage);
if (!contextA || !contextB) {
safe_call_destructor(contextA);
safe_call_destructor(contextB);
return nullptr;
}
return new (storage) ComposeShaderContext(*this, rec, contextA, contextB);
}
SkShader::Context* SkComposeShader::onMakeContext(
const ContextRec& rec, SkArenaAlloc* alloc) const
{
// we preconcat our localMatrix (if any) with the device matrix
// before calling our sub-shaders
SkMatrix tmpM;
tmpM.setConcat(*rec.fMatrix, this->getLocalMatrix());
// Our sub-shaders need to see opaque, so by combining them we don't double-alphatize the
// result. ComposeShader itself will respect the alpha, and post-apply it after calling the
// sub-shaders.
SkPaint opaquePaint(*rec.fPaint);
opaquePaint.setAlpha(0xFF);
ContextRec newRec(rec);
newRec.fMatrix = &tmpM;
newRec.fPaint = &opaquePaint;
SkShader::Context* contextA = fShaderA->makeContext(newRec, alloc);
SkShader::Context* contextB = fShaderB->makeContext(newRec, alloc);
if (!contextA || !contextB) {
return nullptr;
}
return alloc->make<ComposeShaderContext>(*this, rec, contextA, contextB);
}