GrCustomStage::StageKey GrGLShaderBuilder::KeyForTextureAccess(const GrTextureAccess& access,
const GrGLCaps& caps) {
GrCustomStage::StageKey key = 0;
// Assume that swizzle support implies that we never have to modify a shader to adjust
// for texture format/swizzle settings.
if (caps.textureSwizzleSupport()) {
return key;
}
if (texture_requires_alpha_to_red_swizzle(caps, access)) {
key = 1;
}
return key;
}
GrGLShaderBuilder::DstReadKey GrGLShaderBuilder::KeyForDstRead(const GrTexture* dstCopy,
const GrGLCaps& caps) {
uint32_t key = kYesDstRead_DstReadKeyBit;
if (caps.fbFetchSupport()) {
return key;
}
SkASSERT(NULL != dstCopy);
if (!caps.textureSwizzleSupport() && GrPixelConfigIsAlphaOnly(dstCopy->config())) {
// The fact that the config is alpha-only must be considered when generating code.
key |= kUseAlphaConfig_DstReadKeyBit;
}
if (kTopLeft_GrSurfaceOrigin == dstCopy->origin()) {
key |= kTopLeftOrigin_DstReadKeyBit;
}
SkASSERT(static_cast<DstReadKey>(key) == key);
return static_cast<DstReadKey>(key);
}
/**
* Do we need to either map r,g,b->a or a->r. configComponentMask indicates which channels are
* present in the texture's config. swizzleComponentMask indicates the channels present in the
* shader swizzle.
*/
static bool swizzle_requires_alpha_remapping(const GrGLCaps& caps,
uint32_t configComponentMask,
uint32_t swizzleComponentMask) {
if (caps.textureSwizzleSupport()) {
// Any remapping is handled using texture swizzling not shader modifications.
return false;
}
// check if the texture is alpha-only
if (kA_GrColorComponentFlag == configComponentMask) {
if (caps.textureRedSupport() && (kA_GrColorComponentFlag & swizzleComponentMask)) {
// we must map the swizzle 'a's to 'r'.
return true;
}
if (kRGB_GrColorComponentFlags & swizzleComponentMask) {
// The 'r', 'g', and/or 'b's must be mapped to 'a' according to our semantics that
// alpha-only textures smear alpha across all four channels when read.
return true;
}
}
return false;
}
GrBackendEffectFactory::EffectKey GrGLShaderBuilder::KeyForTextureAccess(
const GrTextureAccess& access,
const GrGLCaps& caps) {
GrBackendEffectFactory::EffectKey key = 0;
// Assume that swizzle support implies that we never have to modify a shader to adjust
// for texture format/swizzle settings.
if (!caps.textureSwizzleSupport() && swizzle_requires_alpha_remapping(caps, access)) {
key = 1;
}
#if GR_DEBUG
// Assert that key is set iff the swizzle will be modified.
SkString origString(access.getSwizzle());
origString.prepend(".");
SkString modifiedString;
append_swizzle(&modifiedString, access, caps);
if (!modifiedString.size()) {
modifiedString = ".rgba";
}
GrAssert(SkToBool(key) == (modifiedString != origString));
#endif
return key;
}
