Implement support for KHR_blend_equation_advanced

src/gpu/gl/GrGLCaps.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 GrGLCaps_DEFINED
 #define GrGLCaps_DEFINED
@@ skipping 362 matching lines @@
 
     typedef GrDrawTargetCaps INHERITED;
 };
 
 
 class GrGLSLCaps : public GrShaderCaps {
 public:
     SK_DECLARE_INST_COUNT(GrGLSLCaps)
 
     /**
+    * Indicates how GLSL must interact with advanced blend equations. The KHR extension requires
+    * special layout qualifiers in the fragment shader.
+    */
+    enum AdvancedBlendEqnInteraction {
+        kNotSupported_AdvancedBlendEqnInteraction,         //<! No advanced blend equation support
+        kAutomatic_AdvancedBlendEqnInteraction,            //<! No interaction required
+        kMustEnable_AdvancedBlendEqnInteraction,           //<! Blanket qualifier for all equations
+        kMustEnableSeparately_AdvancedBlendEqnInteraction, //<! Separate qualifiers per equation
+
+        kLast_AdvancedBlendEqnInteraction = kMustEnableSeparately_AdvancedBlendEqnInteraction
+    };
+
+    /**
      * Creates a GrGLSLCaps that advertises no support for any extensions,
      * formats, etc. Call init to initialize from a GrGLContextInfo.
      */
     GrGLSLCaps();
     ~GrGLSLCaps() override {}
 
     GrGLSLCaps(const GrGLSLCaps& caps);
 
     GrGLSLCaps& operator = (const GrGLSLCaps& caps);
 
     /**
      * Resets the caps such that nothing is supported.
      */
     void reset() override;
 
     /**
      * Initializes the GrGLSLCaps to the set of features supported in the current
      * OpenGL context accessible via ctxInfo.
      */
-    bool init(const GrGLContextInfo& ctxInfo, const GrGLInterface* glInterface);
+    bool init(const GrGLContextInfo&, const GrGLInterface*, const GrGLCaps&);
 
     /**
      * Some helper functions for encapsulating various extensions to read FB Buffer on openglES
      *
      * TODO(joshualitt) On desktop opengl 4.2+ we can achieve something similar to this effect
      */
     bool fbFetchSupport() const { return fFBFetchSupport; }
 
     bool fbFetchNeedsCustomOutput() const { return fFBFetchNeedsCustomOutput; }
 
     const char* fbFetchColorName() const { return fFBFetchColorName; }
 
     const char* fbFetchExtensionString() const { return fFBFetchExtensionString; }
 
     bool dropsTileOnZeroDivide() const { return fDropsTileOnZeroDivide; }
 
+    AdvancedBlendEqnInteraction advancedBlendEqnInteraction() const {
+        return fAdvancedBlendEqnInteraction;
+    }
+
+    bool mustEnableAdvancedBlendEquations() const {
+        return fAdvancedBlendEqnInteraction >= kMustEnable_AdvancedBlendEqnInteraction;
+    }
+
     /**
     * Returns a string containing the caps info.
     */
     SkString dump() const override;
 
 private:
     // Must be called after fGeometryShaderSupport is initialized.
     void initShaderPrecisionTable(const GrGLContextInfo&, const GrGLInterface*);
 
     bool fDropsTileOnZeroDivide : 1;
     bool fFBFetchSupport : 1;
     bool fFBFetchNeedsCustomOutput : 1;
 
     const char* fFBFetchColorName;
     const char* fFBFetchExtensionString;
 
+    AdvancedBlendEqnInteraction fAdvancedBlendEqnInteraction;
+
     typedef GrShaderCaps INHERITED;
 };
 
 
 #endif