Refactoring of GPU NormalMap handling out into its own class

src/core/SkLightingShader.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 SkLightingShader_DEFINED
 #define SkLightingShader_DEFINED
 
 #include "SkLights.h"
 #include "SkShader.h"
 
 class SkBitmap;
 class SkMatrix;
 
 class SK_API SkLightingShader {
 public:
+    /** Abstract class that generates or reads in normals for use by SkLightingShader. Currently
+        implements the GPU side only. Not to be used as part of the API yet. Used internally by
+        SkLightingShader.
+    */
+    class NormalSource : public SkFlattenable {
+    public:
+        virtual ~NormalSource();
+
+#if SK_SUPPORT_GPU
+
+        /** Returns a fragment processor that takes no input and outputs a normal (already rotated)

[egdaniel, 2016/06/14 18:30:45]

in general the no input here isn't true. I believe the input will be an
unnormalized vector (distance and direction) to closest edge. It is up to the
subclasses how they will treat this input

[dvonbeck, 2016/06/14 18:41:44]

That would be coming in as a universal though, right? Not as a direct color
input to the fragment shader.

[egdaniel, 2016/06/14 19:01:18]

Ah right this is asFragmentProcessor, I was thinking about the general
NormalSource. Talking to Mike, I think we should update the comment for
NormalSource to say something along the lines of it will take a matrix and
position as input, and will have ways to access necessary geometry information
in order to generate normals.

+            as its output color. To be used as a child fragment processor.
+        */
+        virtual sk_sp<GrFragmentProcessor> asFragmentProcessor(
+                GrContext* context,
+                const SkMatrix& viewM,
+                const SkMatrix* localMatrix,
+                SkFilterQuality filterQuality,
+                SkSourceGammaTreatment gammaTreatment) const = 0;
+#endif
+
+        SK_DEFINE_FLATTENABLE_TYPE(NormalSource)
+    };
+
+    /** Returns a normal source that provides normals sourced from the the normal map argument.
+        Not to be used as part of the API yet. Used internally by SkLightingShader.
+
+        @param  normal                the normal map
+        @param  invNormRotation       rotation applied to the normal map's normals
+        @param  normLocalM            the local matrix for the normal map
+
+        nullptr will be returned if
+            'normal' is empty
+            'normal' too big (> 65535 on either side)
+
+        The normal map is currently assumed to be an 8888 image where the normal at a texel
+        is retrieved by:
+            N.x = R-127;
+            N.y = G-127;
+            N.z = B-127;
+            N.normalize();
+        The +Z axis is thus encoded in RGB as (127, 127, 255) while the -Z axis is
+        (127, 127, 0).
+    */
+    class NormalMapSource {
+    public:
+        static sk_sp<NormalSource> Make(const SkBitmap& normal, const SkVector& invNormRotation,
+                                        const SkMatrix* normLocalM);
+
+        SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
+    };
+
     /** Returns a shader that lights the diffuse and normal maps with a set of lights.
 
         It returns a shader with a reference count of 1.
         The caller should decrement the shader's reference count when done with the shader.
         It is an error for count to be < 2.
         @param  diffuse     the diffuse bitmap
         @param  normal      the normal map
         @param  lights       the lights applied to the normal map
         @param  invNormRotation rotation applied to the normal map's normals
         @param  diffLocalMatrix the local matrix for the diffuse texture
         @param  normLocalMatrix the local matrix for the normal map
 
         nullptr will be returned if:
             either 'diffuse' or 'normal' are empty
             either 'diffuse' or 'normal' are too big (> 65535 on a side)
             'diffuse' and 'normal' aren't the same size
 
         The lighting equation is currently:
             result = LightColor * DiffuseColor * (Normal * LightDir) + AmbientColor
 
         The normal map is currently assumed to be an 8888 image where the normal at a texel
         is retrieved by:
             N.x = R-127;
             N.y = G-127;
             N.z = B-127;
             N.normalize();
         The +Z axis is thus encoded in RGB as (127, 127, 255) while the -Z axis is
         (127, 127, 0).
     */
     static sk_sp<SkShader> Make(const SkBitmap& diffuse, const SkBitmap& normal,

[egdaniel, 2016/06/14 18:30:45]

We should probably also have a version here that takes a NormalSource instead of
a normal bitmap

[egdaniel, 2016/06/14 18:35:48]

Just saw this change in the next CL :)

[dvonbeck, 2016/06/14 18:41:44]

Acknowledged.

                                 sk_sp<SkLights> lights, const SkVector& invNormRotation,
                                 const SkMatrix* diffLocalMatrix, const SkMatrix* normLocalMatrix);
 
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
 };
 
 #endif