Move willUseInputColor check to computeInvariantOutput

include/gpu/GrProcessor.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrProcessor_DEFINED
 #define GrProcessor_DEFINED
 
 #include "GrBackendProcessorFactory.h"
 #include "GrColor.h"
 #include "GrProcessorUnitTest.h"
 #include "GrProgramElement.h"
 #include "GrTextureAccess.h"
+#include "SkMath.h"
 
 class GrContext;
 class GrCoordTransform;
 
 /** Provides custom shader code to the Ganesh shading pipeline. GrProcessor objects *must* be
     immutable: after being constructed, their fields may not change.
 
     Dynamically allocated GrProcessors are managed by a per-thread memory pool. The ref count of an
     processor must reach 0 before the thread terminates and the pool is destroyed. To create a
     static processor use the helper macro GR_CREATE_STATIC_PROCESSOR declared below.
  */
 class GrProcessor : public GrProgramElement {
 public:
     SK_DECLARE_INST_COUNT(GrProcessor)
 
     virtual ~GrProcessor();
 
     struct InvariantOutput{
         InvariantOutput() : fColor(0), fValidFlags(0), fIsSingleComponent(false),
-                            fNonMulStageFound(false) {}
+                            fNonMulStageFound(false), fWillUseInputColor(true) {}
+
+        enum ReadInput {
+            kWill_ReadInput,
+            kWillNot_ReadInput,
+        };
 
         void mulByUnknownOpaqueColor() {
             if (this->isOpaque()) {
                 fValidFlags = kA_GrColorComponentFlag;
                 fIsSingleComponent = false;
             } else {
                 // Since the current state is not opaque we no longer care if the color being
                 // multiplied is opaque.
                 this->mulByUnknownColor(); 
             }
         }
 
         void mulByUnknownColor() {
             if (this->hasZeroAlpha()) {
                 this->internalSetToTransparentBlack();
             } else {
                 this->internalSetToUnknown();
             }
         }
 
         void mulByUnknownAlpha() {
             if (this->hasZeroAlpha()) {
                 this->internalSetToTransparentBlack();
             } else {
                 // We don't need to change fIsSingleComponent in this case
                 fValidFlags = 0;
             }
         }
 
-        void invalidateComponents(uint8_t invalidateFlags) {
+        void mulByKnownAlpha(uint8_t alpha) {
+            if (this->hasZeroAlpha() || 0 == alpha) {
+                this->internalSetToTransparentBlack();
+            } else {
+                if (alpha != 255) {
+                    // Multiply color by alpha
+                    fColor = GrColorPackRGBA(SkMulDiv255Round(GrColorUnpackR(fColor), alpha),
+                                             SkMulDiv255Round(GrColorUnpackG(fColor), alpha),
+                                             SkMulDiv255Round(GrColorUnpackB(fColor), alpha),
+                                             SkMulDiv255Round(GrColorUnpackA(fColor), alpha));
+                }
+            }
+        }
+
+        void invalidateComponents(uint8_t invalidateFlags, ReadInput readsInput) {
             fValidFlags &= ~invalidateFlags;
             fIsSingleComponent = false;
+            if (kWillNot_ReadInput == readsInput) {
+                fWillUseInputColor = false;
+            }
         }
 
-        void setToTransparentBlack() {
-            this->internalSetToTransparentBlack();
-            fNonMulStageFound = true;
-        }
-
-        void setToOther(uint8_t validFlags, GrColor color) {
+        void setToOther(uint8_t validFlags, GrColor color, ReadInput readsInput) {
             fValidFlags = validFlags;
             fColor = color;
             fIsSingleComponent = false;
             fNonMulStageFound = true;
+            if (kWillNot_ReadInput == readsInput) {
+                fWillUseInputColor = false;
+            }
         }
 
-        void setToUnknown() {
+        void setToUnknown(ReadInput readsInput) {
             this->internalSetToUnknown();
             fNonMulStageFound= true;
+            if (kWillNot_ReadInput == readsInput) {
+                fWillUseInputColor = false;
+            }
         }
 
         bool isOpaque() const {
             return ((fValidFlags & kA_GrColorComponentFlag) && 0xFF == GrColorUnpackA(fColor));
         }
 
         bool isSolidWhite() const {
             return (fValidFlags == kRGBA_GrColorComponentFlags && 0xFFFFFFFF == fColor);
         }
 
@@ skipping 27 matching lines @@
          * If alpha is valid, check that any valid R,G,B values are <= A
          */
         SkDEBUGCODE(bool validPreMulColor() const;)
 
         // Friended class that have "controller" code which loop over stages calling
         // computeInvarianteOutput(). These controllers may need to manually adjust the internal
         // members of InvariantOutput
         friend class GrDrawState;
         friend class GrOptDrawState;
         friend class GrPaint;
+        friend class GrProcessor;
 
         GrColor fColor;
         uint32_t fValidFlags;
         bool fIsSingleComponent;
         bool fNonMulStageFound;
+        bool fWillUseInputColor;
     };
 
     /**
      * This function is used to perform optimizations. When called the invarientOuput param
      * indicate whether the input components to this processor in the FS will have known values.
      * In inout the validFlags member is a bitfield of GrColorComponentFlags. The isSingleComponent
      * member indicates whether the input will be 1 or 4 bytes. The function updates the members of
      * inout to indicate known values of its output. A component of the color member only has
      * meaning if the corresponding bit in validFlags is set.
      */
     void computeInvariantOutput(InvariantOutput* inout) const {
+        inout->fWillUseInputColor = true;
         this->onComputeInvariantOutput(inout);
 #ifdef SK_DEBUG
         inout->validate();
 #endif
     }
 
     /** This object, besides creating back-end-specific helper objects, is used for run-time-type-
         identification. The factory should be an instance of templated class,
         GrTBackendProcessorFactory. It is templated on the subclass of GrProcessor. The subclass
         must have a nested type (or typedef) named GLProcessor which will be the subclass of
@@ skipping 79 matching lines @@
 /**
  * This creates a processor outside of the memory pool. The processor's destructor will be called
  * at global destruction time. NAME will be the name of the created instance.
  */
 #define GR_CREATE_STATIC_PROCESSOR(NAME, PROC_CLASS, ARGS)                                 \
 static SkAlignedSStorage<sizeof(PROC_CLASS)> g_##NAME##_Storage;                           \
 static PROC_CLASS* NAME SkNEW_PLACEMENT_ARGS(g_##NAME##_Storage.get(), PROC_CLASS, ARGS);  \
 static SkAutoTDestroy<GrProcessor> NAME##_ad(NAME);
 
 #endif