added emitChild() to GrGLFragmentProcessor; removed AutoFragmentChildProcAdvance class

src/gpu/gl/GrGLFragmentProcessor.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLFragmentProcessor.h"
 #include "GrFragmentProcessor.h"
+#include "builders/GrGLFragmentShaderBuilder.h"
+#include "builders/GrGLProgramBuilder.h"
 
 void GrGLFragmentProcessor::setData(const GrGLProgramDataManager& pdman,
                                     const GrFragmentProcessor& processor) {
     this->onSetData(pdman, processor);
     SkASSERT(fChildProcessors.count() == processor.numChildProcessors());
     for (int i = 0; i < fChildProcessors.count(); ++i) {
         fChildProcessors[i]->setData(pdman, processor.childProcessor(i));
     }
 }
+
+void GrGLFragmentProcessor::emitChild(int childIndex, const char* inputColor,
+                                      SkString* outputColor, EmitArgs& args) {
+    GrGLFragmentBuilder* fb = args.fBuilder->getFragmentShaderBuilder();
+    fb->onBeforeChildProcEmitCode();  // call first so mangleString is updated
+
+    const GrFragmentProcessor& childProc = args.fFp.childProcessor(childIndex);
+
+    // Mangle the name of the outputColor
+    outputColor->set(args.fOutputColor);
+    outputColor->append(fb->getMangleStringThisLevel());
+
+    /*
+     * 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 must do a
+     * backwards linear search on coords and samplers.
+     *
+     * 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 B, we want the
+     * EmitArgs that's passed onto B 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 [b1,b2,c1] to pass on to B. We can do this with a backwards linear
+     * search since we know that D's subtree has 6 transforms and B's subtree has 3 transforms (by
+     * calling D.numTextures() and B.numTextures()), so we know the start of B's transforms is 9
+     * from the end of A's transforms.  We cannot do this with a forwards linear search since we
+     * don't know how many transforms belong to A (A.numTextures() will return 10, not 1), so
+     * we wouldn't know how many transforms to initially skip in A's array if using a forward linear
+     * search.
+     * Textures work the same way as transforms.
+     */
+    int firstCoordAt = args.fFp.numTransforms();
+    int firstSamplerAt = args.fFp.numTextures();
+    for (int i = args.fFp.numChildProcessors() - 1; 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->codeAppendf("vec4 %s;\n", outputColor->c_str());
+    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->c_str(),
+                       inputColor,
+                       childCoords,
+                       childSamplers);
+    this->childProcessor(childIndex)->emitCode(childArgs);
+    fb->codeAppend("}\n");
+
+    fb->onAfterChildProcEmitCode();
+}