Make GPU coord transforms automatic

src/gpu/gl/GrGLCoordTransform.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 GrGLCoordTransform_DEFINED
+#define GrGLCoordTransform_DEFINED
+
+#include "GrBackendEffectFactory.h"
+#include "GrCoordTransform.h"
+#include "GrGLUniformManager.h"
+
+class GrTexture;
+class GrGLShaderBuilder;
+
+/**
+ * This is a helper class used by the framework to implement a coordinate transform that operates on
+ * incoming coords in the vertex shader and writes them to a varying to be used in the fragment
+ * shader. Effects should not use this class directly, but instead call GrEffect::addCoordTransform.
+ * When the input coords are local coordinates this class accounts for the coord change matrix
+ * communicated via GrDrawEffect. The input coords may also be positions and in this case the coord
+ * change matrix is ignored. The GrGLCoordTransform may emit different code based on the type of
+ * matrix and thus must contribute to the effect's key.
+ *
+ * This class cannot be used to apply a matrix to coordinates that come in the form of custom vertex
+ * attributes.
+ */
+class GrGLCoordTransform {
+private:
+    // We specialize the generated code for each of these matrix types.
+    enum MatrixTypes {
+        kIdentity_MatrixType    = 0,
+        kTrans_MatrixType       = 1,
+        kNoPersp_MatrixType     = 2,
+        kGeneral_MatrixType     = 3,
+    };
+    // The key for is made up of a matrix type and a bit that indicates the source of the input
+    // coords.
+    enum {
+        kMatrixTypeKeyBits      = 2,
+        kMatrixTypeKeyMask      = (1 << kMatrixTypeKeyBits) - 1,
+        kPositionCoords_Flag    = (1 << kMatrixTypeKeyBits),
+        kKeyBitsPrivate         = kMatrixTypeKeyBits + 1,
+    };
+
+public:
+
+    typedef GrBackendEffectFactory::EffectKey EffectKey;
+
+    /**
+     * A GrGLCoordTransform key is kKeyBits long. The framework automatically generates and includes
+     * these in EffectKeys.
+     */
+    enum {
+        kKeyBits = kKeyBitsPrivate,
+        kKeyMask = (1 << kKeyBits) - 1,
+    };
+
+    GrGLCoordTransform() { fPrevMatrix = SkMatrix::InvalidMatrix(); }
+
+    /**
+     * Generates the key for the portion of the code emitted by this class's emitCode() function.
+     */
+    static EffectKey GenKey(const GrDrawEffect&, int transformIdx);
+
+    /**
+     * Stores the name and type of a transformed set of coordinates. This class is passed to
+     * GrGLEffect::emitCode.
+     */
+    class TransformedCoords {
+    public:
+        const char* c_str() const { return fName.c_str(); }
+        GrSLType type() const { return fType; }
+        const SkString& getName() const { return fName; }
+        // TODO: Remove the VS name when we have vertexless shaders, and gradients are reworked.
+        const SkString& getVSName() const { return fVSName; }
+
+    private:
+        friend class GrGLCoordTransform;
+
+        SkString fName;
+        GrSLType fType;
+        SkString fVSName;
+    };
+
+    /**
+     * Emits code to implement the matrix in the VS. A varying is added as an output of the VS and
+     * input to the FS. The varying may be either a vec2f or vec3f depending upon whether
+     * perspective interpolation is required or not. The names of the varying in the VS and FS as
+     * well as its type are written to the TransformedCoords* object. The suffix is an optional
+     * parameter that can be used to make all variables emitted by the object unique within a stage.
+     * It is only necessary if multiple GrGLCoordTransform objects are used by a single GrGLEffect.
+     */
+    void emitCode(GrGLShaderBuilder*, EffectKey, TransformedCoords*, int suffix = 0);
+
+    /**
+     * Call from a GrGLEffect's subclass to update the texture matrix. The matrix and reverseY value
+     * should match those used with GenKey.
+     */
+    void setData(const GrGLUniformManager&, const GrDrawEffect&, int transformIdx);
+
+    GrGLUniformManager::UniformHandle fUni;
+    GrSLType                          fUniType;
+    SkMatrix                          fPrevMatrix;
+};
+
+#endif