Separate user and raw stencil settings

src/gpu/GrPipelineBuilder.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrPipelineBuilder_DEFINED
 #define GrPipelineBuilder_DEFINED
 
@@ skipping 181 matching lines @@
      * @param target  The render target to set.
      */
     void setRenderTarget(GrRenderTarget* target) { fRenderTarget.reset(SkSafeRef(target)); }
 
     /// @}
 
     ///////////////////////////////////////////////////////////////////////////
     /// @name Stencil
     ////
 
-    const GrStencilSettings& getStencil() const { return fStencilSettings; }
+    bool hasUserStencilSettings() const {
+        return &GrUserStencilSettings::kUnused != fUserStencilSettings;
+    }
+    const GrUserStencilSettings* getUserStencil() const { return fUserStencilSettings; }
 
     /**
-     * Sets the stencil settings to use for the next draw.
-     * Changing the clip has the side-effect of possibly zeroing
-     * out the client settable stencil bits. So multipass algorithms
-     * using stencil should not change the clip between passes.
+     * Sets the user stencil settings for the next draw.
+     * This class only stores pointers to stencil settings objects.
+     * The caller guarantees the pointer will remain valid until it

[bsalomon, 2016/05/10 14:06:21]

It seems like you've designed GrUserStencilSettings such that this must be true,
or am I missing a possibility?

[Chris Dalton, 2016/05/10 16:39:30]

Unfortunately it can still be declared in non-static scope. e.g:

 constexpr GrUserStencilSettings stackAllocated (...);
 pb.setUserStencil(&stackAllocated);

[bsalomon, 2016/05/10 20:10:58]

Right, of course.

+     * changes or goes out of scope.
      * @param settings  the stencil settings to use.
      */
-    void setStencil(const GrStencilSettings& settings) { fStencilSettings = settings; }
-
-    GrStencilSettings* stencil() { return &fStencilSettings; }
-
-    /**
-     * AutoRestoreStencil
-     *
-     * This simple struct saves and restores the stencil settings
-     * This class can transiently modify its "const" GrPipelineBuilder object but will restore it
-     * when done - so it is notionally "const" correct.
-     */
-    class AutoRestoreStencil : public ::SkNoncopyable {
-    public:
-        AutoRestoreStencil() : fPipelineBuilder(nullptr) {}
-
-        AutoRestoreStencil(const GrPipelineBuilder& ds) : fPipelineBuilder(nullptr) { this->set(&ds); }
-
-        ~AutoRestoreStencil() { this->set(nullptr); }
-
-        void set(const GrPipelineBuilder* ds) {
-            if (fPipelineBuilder) {
-                fPipelineBuilder->setStencil(fStencilSettings);
-            }
-            fPipelineBuilder = const_cast<GrPipelineBuilder*>(ds);
-            if (ds) {
-                fStencilSettings = ds->getStencil();
-            }
-        }
-
-        bool isSet() const { return SkToBool(fPipelineBuilder); }
-
-        void setStencil(const GrStencilSettings& settings) {
-            SkASSERT(this->isSet());
-            fPipelineBuilder->setStencil(settings);
-        }
-
-    private:
-        // notionally const (as marginalia)
-        GrPipelineBuilder*  fPipelineBuilder;
-        GrStencilSettings   fStencilSettings;
-    };
-
+    void setUserStencil(const GrUserStencilSettings* settings) { fUserStencilSettings = settings; }
+    void disableUserStencil() { fUserStencilSettings = &GrUserStencilSettings::kUnused; }
 
     /// @}
 
     ///////////////////////////////////////////////////////////////////////////
     /// @name State Flags
     ////
 
     /**
      *  Flags that affect rendering. Controlled using enable/disableState(). All
      *  default to disabled.
@@ skipping 101 matching lines @@
 
 private:
     // Some of the auto restore objects assume that no effects are removed during their lifetime.
     // This is used to assert that this condition holds.
     SkDEBUGCODE(mutable int fBlockEffectRemovalCnt;)
 
     typedef SkSTArray<4, const GrFragmentProcessor*, true> FragmentProcessorArray;
 
     SkAutoTUnref<GrRenderTarget>            fRenderTarget;
     uint32_t                                fFlags;
-    GrStencilSettings                       fStencilSettings;
+    const GrUserStencilSettings*            fUserStencilSettings;
     DrawFace                                fDrawFace;
     mutable SkAutoTUnref<const GrXPFactory> fXPFactory;
     FragmentProcessorArray                  fColorFragmentProcessors;
     FragmentProcessorArray                  fCoverageFragmentProcessors;
     GrClip                                  fClip;
 
     friend class GrPipeline;
     friend class GrDrawTarget;
 };
 
 #endif