void GrGLFragmentProcessor::emitChild(int childIndex, const char* inputColor,
const char* outputColor, EmitArgs& args) {
GrGLFragmentBuilder* fb = args.fBuilder->getFragmentShaderBuilder();
fb->onBeforeChildProcEmitCode(); // call first so mangleString is updated
const GrFragmentProcessor& childProc = args.fFp.childProcessor(childIndex);
/*
* We now want to find the subset of coords and samplers that belong to the child and its
* descendants and put that into childCoords and childSamplers. To do so, we'll do a forwards
* linear search.
*
* Explanation:
* Each GrFragmentProcessor has a copy of all the transforms and textures of itself and
* all procs in its subtree. For example, suppose we have frag proc A, who has two children B
* and D. B has a child C, and D has two children E and F. Each frag proc's transforms array
* contains its own transforms, followed by the transforms of all its descendants (i.e. preorder
* traversal). Suppose procs A, B, C, D, E, F have 1, 2, 1, 1, 3, 2 transforms respectively.
*
* (A)
* [a1,b1,b2,c1,d1,e1,e2,e3,f1,f2]
* / \
* / \
* (B) (D)
* [b1,b2,c1] [d1,e1,e2,e3,f1,f2]
* / / \
* / / \
* (C) (E) (F)
* [c1] [e1,e2,e3] [f1,f2]
*
* So if we're inside proc A's emitCode, and A is about to call emitCode on proc D, we want the
* EmitArgs that's passed onto D to only contain its and its descendants' coords. The
* EmitArgs given to A would contain the transforms [a1,b1,b2,c1,d1,e1,e2,e3,f1,f2], and we want
* to extract the subset [d1,e1,e2,e3,f1,f2] to pass on to D. We can do this with a linear
* search since we know that A has 1 transform (using A.numTransformsExclChildren()), and B's
* subtree has 3 transforms (using B.numTransforms()), so we know the start of D's transforms is
* 4 after the start of A's transforms.
* Textures work the same way as transforms.
*/
int firstCoordAt = args.fFp.numTransformsExclChildren();
int firstSamplerAt = args.fFp.numTexturesExclChildren();
for (int i = 0; i < childIndex; ++i) {
firstCoordAt += args.fFp.childProcessor(i).numTransforms();
firstSamplerAt += args.fFp.childProcessor(i).numTextures();
}
TransformedCoordsArray childCoords;
TextureSamplerArray childSamplers;
if (childProc.numTransforms() > 0) {
childCoords.push_back_n(childProc.numTransforms(), &args.fCoords[firstCoordAt]);
}
if (childProc.numTextures() > 0) {
childSamplers.push_back_n(childProc.numTextures(), &args.fSamplers[firstSamplerAt]);
}
// emit the code for the child in its own scope
fb->codeAppend("{\n");
fb->codeAppendf("// Child Index %d (mangle: %s): %s\n", childIndex,
fb->getMangleString().c_str(), childProc.name());
EmitArgs childArgs(args.fBuilder,
childProc,
outputColor,
inputColor,
childCoords,
childSamplers);
this->childProcessor(childIndex)->emitCode(childArgs);
fb->codeAppend("}\n");
fb->onAfterChildProcEmitCode();
}
