Revert "Move DstCopy on gpu into the GrXferProcessor."

This reverts commit 74a11753604768bf461b80cabb66060e8564d82c.

TBR=joshualitt@google.com,bsalomon@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/896163003

4 files changed, 61 insertions, 2 deletions

diff --git a/src/gpu/gl/builders/GrGLFragmentShaderBuilder.cpp b/src/gpu/gl/builders/GrGLFragmentShaderBuilder.cpp
index 86c622d456..61932f3084 100644
--- a/src/gpu/gl/builders/GrGLFragmentShaderBuilder.cpp
+++ b/src/gpu/gl/builders/GrGLFragmentShaderBuilder.cpp
@@ -179,9 +179,56 @@ const char* GrGLFragmentShaderBuilder::dstColor() {
             fbFetchColorName = declared_color_output_name();
         }
         return fbFetchColorName;
-    } else {
+    } else if (fProgramBuilder->fUniformHandles.fDstCopySamplerUni.isValid()) {
         return kDstCopyColorName;
-    } 
+    } else {
+        return "";
+    }
+}
+
+void GrGLFragmentShaderBuilder::emitCodeToReadDstTexture() {
+    bool topDown = SkToBool(kTopLeftOrigin_DstReadKeyBit & fProgramBuilder->header().fDstReadKey);
+    const char* dstCopyTopLeftName;
+    const char* dstCopyCoordScaleName;
+    const char* dstCopySamplerName;
+    uint32_t configMask;
+    if (SkToBool(kUseAlphaConfig_DstReadKeyBit & fProgramBuilder->header().fDstReadKey)) {
+        configMask = kA_GrColorComponentFlag;
+    } else {
+        configMask = kRGBA_GrColorComponentFlags;
+    }
+    fProgramBuilder->fUniformHandles.fDstCopySamplerUni =
+            fProgramBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
+                                        kSampler2D_GrSLType,
+                                        kDefault_GrSLPrecision,
+                                        "DstCopySampler",
+                                        &dstCopySamplerName);
+    fProgramBuilder->fUniformHandles.fDstCopyTopLeftUni =
+            fProgramBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
+                                        kVec2f_GrSLType,
+                                        kDefault_GrSLPrecision,
+                                        "DstCopyUpperLeft",
+                                        &dstCopyTopLeftName);
+    fProgramBuilder->fUniformHandles.fDstCopyScaleUni =
+            fProgramBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
+                                        kVec2f_GrSLType,
+                                        kDefault_GrSLPrecision,
+                                        "DstCopyCoordScale",
+                                        &dstCopyCoordScaleName);
+    const char* fragPos = this->fragmentPosition();
+
+    this->codeAppend("// Read color from copy of the destination.\n");
+    this->codeAppendf("vec2 _dstTexCoord = (%s.xy - %s) * %s;",
+                      fragPos, dstCopyTopLeftName, dstCopyCoordScaleName);
+    if (!topDown) {
+        this->codeAppend("_dstTexCoord.y = 1.0 - _dstTexCoord.y;");
+    }
+    this->codeAppendf("vec4 %s = ", GrGLFragmentShaderBuilder::kDstCopyColorName);
+    this->appendTextureLookup(dstCopySamplerName,
+                              "_dstTexCoord",
+                              configMask,
+                              "rgba");
+    this->codeAppend(";");
 }
 
 void GrGLFragmentShaderBuilder::enableCustomOutput() {
diff --git a/src/gpu/gl/builders/GrGLFragmentShaderBuilder.h b/src/gpu/gl/builders/GrGLFragmentShaderBuilder.h
index 903c5e1d7b..688bbe6269 100644
--- a/src/gpu/gl/builders/GrGLFragmentShaderBuilder.h
+++ b/src/gpu/gl/builders/GrGLFragmentShaderBuilder.h
@@ -97,6 +97,7 @@ public:
 
 private:
     // Private public interface, used by GrGLProgramBuilder to build a fragment shader
+    void emitCodeToReadDstTexture();
     void enableCustomOutput();
     void enableSecondaryOutput();
     const char* getPrimaryColorOutputName() const;
diff --git a/src/gpu/gl/builders/GrGLProgramBuilder.cpp b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
index bb278be395..088169622c 100644
--- a/src/gpu/gl/builders/GrGLProgramBuilder.cpp
+++ b/src/gpu/gl/builders/GrGLProgramBuilder.cpp
@@ -56,6 +56,12 @@ GrGLProgram* GrGLProgramBuilder::CreateProgram(const DrawArgs& args, GrGLGpu* gp
 
     GrGLProgramBuilder* pb = builder.get();
 
+    // emit code to read the dst copy texture, if necessary
+    if (GrGLFragmentShaderBuilder::kNoDstRead_DstReadKey != pb->header().fDstReadKey &&
+        !gpu->glCaps().fbFetchSupport()) {
+        pb->fFS.emitCodeToReadDstTexture();
+    }
+
     // TODO: Once all stages can handle taking a float or vec4 and correctly handling them we can
     // seed correctly here
     GrGLSLExpr4 inputColor;
diff --git a/src/gpu/gl/builders/GrGLProgramBuilder.h b/src/gpu/gl/builders/GrGLProgramBuilder.h
index a9288cc9b0..4b40cefad0 100644
--- a/src/gpu/gl/builders/GrGLProgramBuilder.h
+++ b/src/gpu/gl/builders/GrGLProgramBuilder.h
@@ -267,6 +267,11 @@ public:
         // We use the render target height to provide a y-down frag coord when specifying
         // origin_upper_left is not supported.
         UniformHandle       fRTHeightUni;
+
+        // Uniforms for computing texture coords to do the dst-copy lookup
+        UniformHandle       fDstCopyTopLeftUni;
+        UniformHandle       fDstCopyScaleUni;
+        UniformHandle       fDstCopySamplerUni;
     };
 
 protected: