Create Read-only Base class for GrDrawState that holds data members and getters

src/gpu/GrRODrawState.h

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrRODrawState_DEFINED
+#define GrRODrawState_DEFINED
+
+#include "GrStencil.h"
+#include "GrEffectStage.h"
+#include "SkMatrix.h"
+
+class GrDrawTargetCaps;
+class GrPaint;
+class GrRenderTarget;
+class GrTexture;
+
+/**
+ * Read-only base class for GrDrawState. This class contains all the necessary data to represent a
+ * canonical DrawState. All methods in the class are const, thus once created the data in the class
+ * cannot be changed.
+ */
+class GrRODrawState : public SkRefCnt {
+public:
+    SK_DECLARE_INST_COUNT(GrRODrawState)
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name Vertex Attributes
+    ////
+
+    enum {
+        kMaxVertexAttribCnt = kLast_GrVertexAttribBinding + 4,
+    };
+
+    const GrVertexAttrib* getVertexAttribs() const { return fVAPtr; }
+    int getVertexAttribCount() const { return fVACount; }
+
+    size_t getVertexSize() const { return fVertexSize; }
+
+    /**
+     * Getters for index into getVertexAttribs() for particular bindings. -1 is returned if the
+     * binding does not appear in the current attribs. These bindings should appear only once in
+     * the attrib array.
+     */
+
+    int positionAttributeIndex() const {
+        return fFixedFunctionVertexAttribIndices[kPosition_GrVertexAttribBinding];
+    }
+    int localCoordAttributeIndex() const {
+        return fFixedFunctionVertexAttribIndices[kLocalCoord_GrVertexAttribBinding];
+    }
+    int colorVertexAttributeIndex() const {
+        return fFixedFunctionVertexAttribIndices[kColor_GrVertexAttribBinding];
+    }
+    int coverageVertexAttributeIndex() const {
+        return fFixedFunctionVertexAttribIndices[kCoverage_GrVertexAttribBinding];
+    }
+
+    bool hasLocalCoordAttribute() const {
+        return -1 != fFixedFunctionVertexAttribIndices[kLocalCoord_GrVertexAttribBinding];
+    }
+    bool hasColorVertexAttribute() const {
+        return -1 != fFixedFunctionVertexAttribIndices[kColor_GrVertexAttribBinding];
+    }
+    bool hasCoverageVertexAttribute() const {
+        return -1 != fFixedFunctionVertexAttribIndices[kCoverage_GrVertexAttribBinding];
+    }
+
+    bool validateVertexAttribs() const;
+
+    /// @}
+
+    /**
+     * Determines whether the output coverage is guaranteed to be one for all pixels hit by a draw.
+     */
+    bool hasSolidCoverage() const;
+
+    /// @}
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name Color
+    ////
+
+    GrColor getColor() const { return fColor; }
+
+    /// @}
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name Coverage
+    ////
+
+    uint8_t getCoverage() const { return fCoverage; }
+
+    GrColor getCoverageColor() const {
+        return GrColorPackRGBA(fCoverage, fCoverage, fCoverage, fCoverage);
+    }
+
+    /// @}
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name Effect Stages
+    /// Each stage hosts a GrEffect. The effect produces an output color or coverage in the fragment
+    /// shader. Its inputs are the output from the previous stage as well as some variables
+    /// available to it in the fragment and vertex shader (e.g. the vertex position, the dst color,
+    /// the fragment position, local coordinates).
+    ///
+    /// The stages are divided into two sets, color-computing and coverage-computing. The final
+    /// color stage produces the final pixel color. The coverage-computing stages function exactly
+    /// as the color-computing but the output of the final coverage stage is treated as a fractional
+    /// pixel coverage rather than as input to the src/dst color blend step.
+    ///
+    /// The input color to the first color-stage is either the constant color or interpolated
+    /// per-vertex colors. The input to the first coverage stage is either a constant coverage
+    /// (usually full-coverage) or interpolated per-vertex coverage.
+    ///
+    /// See the documentation of kCoverageDrawing_StateBit for information about disabling the
+    /// the color / coverage distinction.
+    ////
+
+    int numColorStages() const { return fColorStages.count(); }
+    int numCoverageStages() const { return fCoverageStages.count(); }
+    int numTotalStages() const { return this->numColorStages() + this->numCoverageStages(); }
+
+    const GrEffectStage& getColorStage(int stageIdx) const { return fColorStages[stageIdx]; }
+    const GrEffectStage& getCoverageStage(int stageIdx) const { return fCoverageStages[stageIdx]; }
+
+    /**
+     * Checks whether any of the effects will read the dst pixel color.
+     */
+    bool willEffectReadDstColor() const;
+
+    /// @}
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name Blending
+    ////
+
+    GrBlendCoeff getSrcBlendCoeff() const { return fSrcBlend; }
+    GrBlendCoeff getDstBlendCoeff() const { return fDstBlend; }
+
+    void getDstBlendCoeff(GrBlendCoeff* srcBlendCoeff,
+                          GrBlendCoeff* dstBlendCoeff) const {
+        *srcBlendCoeff = fSrcBlend;
+        *dstBlendCoeff = fDstBlend;
+    }
+
+    /**
+     * Retrieves the last value set by setBlendConstant()
+     * @return the blending constant value
+     */
+    GrColor getBlendConstant() const { return fBlendConstant; }
+
+    /**
+     * Determines whether multiplying the computed per-pixel color by the pixel's fractional
+     * coverage before the blend will give the correct final destination color. In general it
+     * will not as coverage is applied after blending.
+     */
+    bool canTweakAlphaForCoverage() const;
+
+    /**
+     * Optimizations for blending / coverage to that can be applied based on the current state.
+     */
+    enum BlendOptFlags {
+        /**
+         * No optimization
+         */
+        kNone_BlendOpt                  = 0,
+        /**
+         * Don't draw at all
+         */
+        kSkipDraw_BlendOptFlag          = 0x1,
+        /**
+         * The coverage value does not have to be computed separately from alpha, the output
+         * color can be the modulation of the two.
+         */
+        kCoverageAsAlpha_BlendOptFlag   = 0x2,
+        /**
+         * Instead of emitting a src color, emit coverage in the alpha channel and r,g,b are
+         * "don't cares".
+         */
+        kEmitCoverage_BlendOptFlag      = 0x4,
+        /**
+         * Emit transparent black instead of the src color, no need to compute coverage.
+         */
+        kEmitTransBlack_BlendOptFlag    = 0x8,
+        /**
+         * Flag used to invalidate the cached BlendOptFlags, OptSrcCoeff, and OptDstCoeff cached by
+         * the get BlendOpts function.
+         */
+        kInvalid_BlendOptFlag           = 1 << 31,
+    };
+    GR_DECL_BITFIELD_OPS_FRIENDS(BlendOptFlags);
+
+    /// @}
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name View Matrix
+    ////
+
+    /**
+     * Retrieves the current view matrix
+     * @return the current view matrix.
+     */
+    const SkMatrix& getViewMatrix() const { return fViewMatrix; }
+
+    /**
+     *  Retrieves the inverse of the current view matrix.
+     *
+     *  If the current view matrix is invertible, return true, and if matrix
+     *  is non-null, copy the inverse into it. If the current view matrix is
+     *  non-invertible, return false and ignore the matrix parameter.
+     *
+     * @param matrix if not null, will receive a copy of the current inverse.
+     */
+    bool getViewInverse(SkMatrix* matrix) const {
+        // TODO: determine whether we really need to leave matrix unmodified
+        // at call sites when inversion fails.
+        SkMatrix inverse;
+        if (fViewMatrix.invert(&inverse)) {
+            if (matrix) {
+                *matrix = inverse;
+            }
+            return true;
+        }
+        return false;
+    }
+
+    /// @}
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name Render Target
+    ////
+
+    /**
+     * Retrieves the currently set render-target.
+     *
+     * @return    The currently set render target.
+     */
+    const GrRenderTarget* getRenderTarget() const { return fRenderTarget.get(); }
+    GrRenderTarget* getRenderTarget() { return fRenderTarget.get(); }
+
+    /// @}
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name Stencil
+    ////
+
+    const GrStencilSettings& getStencil() const { return fStencilSettings; }
+
+    /// @}
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name State Flags
+    ////
+
+    /**
+     *  Flags that affect rendering. Controlled using enable/disableState(). All
+     *  default to disabled.
+     */
+    enum StateBits {
+        /**
+         * Perform dithering. TODO: Re-evaluate whether we need this bit
+         */
+        kDither_StateBit        = 0x01,
+        /**
+         * Perform HW anti-aliasing. This means either HW FSAA, if supported by the render target,
+         * or smooth-line rendering if a line primitive is drawn and line smoothing is supported by
+         * the 3D API.
+         */
+        kHWAntialias_StateBit   = 0x02,
+        /**
+         * Draws will respect the clip, otherwise the clip is ignored.
+         */
+        kClip_StateBit          = 0x04,
+        /**
+         * Disables writing to the color buffer. Useful when performing stencil
+         * operations.
+         */
+        kNoColorWrites_StateBit = 0x08,
+
+        /**
+         * Usually coverage is applied after color blending. The color is blended using the coeffs
+         * specified by setBlendFunc(). The blended color is then combined with dst using coeffs
+         * of src_coverage, 1-src_coverage. Sometimes we are explicitly drawing a coverage mask. In
+         * this case there is no distinction between coverage and color and the caller needs direct
+         * control over the blend coeffs. When set, there will be a single blend step controlled by
+         * setBlendFunc() which will use coverage*color as the src color.
+         */
+         kCoverageDrawing_StateBit = 0x10,
+
+        // Users of the class may add additional bits to the vector
+        kDummyStateBit,
+        kLastPublicStateBit = kDummyStateBit-1,
+    };
+
+    bool isStateFlagEnabled(uint32_t stateBit) const { return 0 != (stateBit & fFlagBits); }
+
+    bool isDitherState() const { return 0 != (fFlagBits & kDither_StateBit); }
+    bool isHWAntialiasState() const { return 0 != (fFlagBits & kHWAntialias_StateBit); }
+    bool isClipState() const { return 0 != (fFlagBits & kClip_StateBit); }
+    bool isColorWriteDisabled() const { return 0 != (fFlagBits & kNoColorWrites_StateBit); }
+    bool isCoverageDrawing() const { return 0 != (fFlagBits & kCoverageDrawing_StateBit); }
+
+    /// @}
+
+    ///////////////////////////////////////////////////////////////////////////
+    /// @name Face Culling
+    ////
+
+    enum DrawFace {
+        kInvalid_DrawFace = -1,
+
+        kBoth_DrawFace,
+        kCCW_DrawFace,
+        kCW_DrawFace,
+    };
+
+    /**
+     * Gets whether the target is drawing clockwise, counterclockwise,
+     * or both faces.
+     * @return the current draw face(s).
+     */
+    DrawFace getDrawFace() const { return fDrawFace; }
+
+    /// @}
+
+    ///////////////////////////////////////////////////////////////////////////
+
+    /** Return type for CombineIfPossible. */
+    enum CombinedState {
+        /** The GrDrawStates cannot be combined. */
+        kIncompatible_CombinedState,
+        /** Either draw state can be used in place of the other. */
+        kAOrB_CombinedState,
+        /** Use the first draw state. */
+        kA_CombinedState,
+        /** Use the second draw state. */
+        kB_CombinedState,
+    };
+
+    GrRODrawState& operator= (const GrRODrawState& that);
+
+protected:
+    bool isEqual(const GrRODrawState& that) const;
+
+    // These fields are roughly sorted by decreasing likelihood of being different in op==
+    SkAutoTUnref<GrRenderTarget>        fRenderTarget;
+    GrColor                             fColor;
+    SkMatrix                            fViewMatrix;
+    GrColor                             fBlendConstant;
+    uint32_t                            fFlagBits;
+    const GrVertexAttrib*               fVAPtr;
+    int                                 fVACount;
+    size_t                              fVertexSize;
+    GrStencilSettings                   fStencilSettings;
+    uint8_t                             fCoverage;
+    DrawFace                            fDrawFace;
+    GrBlendCoeff                        fSrcBlend;
+    GrBlendCoeff                        fDstBlend;
+
+    typedef SkSTArray<4, GrEffectStage> EffectStageArray;
+    EffectStageArray                    fColorStages;
+    EffectStageArray                    fCoverageStages;
+
+    mutable GrBlendCoeff                fOptSrcBlend;
+    mutable GrBlendCoeff                fOptDstBlend;
+    mutable BlendOptFlags               fBlendOptFlags;
+
+    // This is simply a different representation of info in fVertexAttribs and thus does
+    // not need to be compared in op==.
+    int fFixedFunctionVertexAttribIndices[kGrFixedFunctionVertexAttribBindingCnt];
+
+private:
+    typedef SkRefCnt INHERITED;
+};
+
+GR_MAKE_BITFIELD_OPS(GrRODrawState::BlendOptFlags);
+
+#endif