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 /*

  * Copyright 2011 Google Inc.

  *

  * Use of this source code is governed by a BSD-style license that can be

  * found in the LICENSE file.

  */

 #ifndef GrPaint_DEFINED

 #define GrPaint_DEFINED

 #include "GrColor.h"

 #include "GrEffectStage.h"

 #include "SkXfermode.h"

 /**

  * The paint describes how color and coverage are computed at each pixel by GrContext draw

  * functions and the how color is blended with the destination pixel.

  *

  * The paint allows installation of custom color and coverage stages. New types of stages are

  * created by subclassing GrEffect.

  *

  * The primitive color computation starts with the color specified by setColor(). This color is the

  * input to the first color stage. Each color stage feeds its output to the next color stage. The

  * final color stage's output color is input to the color filter specified by

  * setXfermodeColorFilter which produces the final source color, S.

  *

  * Fractional pixel coverage follows a similar flow. The coverage is initially the value specified

  * by setCoverage(). This is input to the first coverage stage. Coverage stages are chained

  * together in the same manner as color stages. The output of the last stage is modulated by any

  * fractional coverage produced by anti-aliasing. This last step produces the final coverage, C.

  *

  * setBlendFunc() specifies blending coefficients for S (described above) and D, the initial value

  * of the destination pixel, labeled Bs and Bd respectively. The final value of the destination

  * pixel is then D' = (1-C)*D + C*(Bd*D + Bs*S).

  *

  * Note that the coverage is applied after the blend. This is why they are computed as distinct

  * values.

  *

  * TODO: Encapsulate setXfermodeColorFilter in a GrEffect and remove from GrPaint.

  */

 class GrPaint {

 public:

     GrPaint() { this->reset(); }

     GrPaint(const GrPaint& paint) { *this = paint; }

     ~GrPaint() {}

     /**

      * Sets the blending coefficients to use to blend the final primitive color with the

      * destination color. Defaults to kOne for src and kZero for dst (i.e. src mode).

      */

     void setBlendFunc(GrBlendCoeff srcCoeff, GrBlendCoeff dstCoeff) {

         fSrcBlendCoeff = srcCoeff;

         fDstBlendCoeff = dstCoeff;

     }

     GrBlendCoeff getSrcBlendCoeff() const { return fSrcBlendCoeff; }

     GrBlendCoeff getDstBlendCoeff() const { return fDstBlendCoeff; }

     /**

      * The initial color of the drawn primitive. Defaults to solid white.

      */

     void setColor(GrColor color) { fColor = color; }

     GrColor getColor() const { return fColor; }

     /**

      * Applies fractional coverage to the entire drawn primitive. Defaults to 0xff.

      */

     void setCoverage(uint8_t coverage) { fCoverage = coverage; }

     uint8_t getCoverage() const { return fCoverage; }

     /**

      * Should primitives be anti-aliased or not. Defaults to false.

      */

     void setAntiAlias(bool aa) { fAntiAlias = aa; }

     bool isAntiAlias() const { return fAntiAlias; }

     /**

      * Should dithering be applied. Defaults to false.

      */

     void setDither(bool dither) { fDither = dither; }

     bool isDither() const { return fDither; }

     /**

      * Appends an additional color effect to the color computation.

      */

     const GrEffectRef* addColorEffect(const GrEffectRef* effect, int attr0 = -1, int attr1 = -1) {

         SkASSERT(NULL != effect);

         if (!(*effect)->willUseInputColor()) {

             fColorStages.reset();

         }

         SkNEW_APPEND_TO_TARRAY(&fColorStages, GrEffectStage, (effect, attr0, attr1));

         return effect;

     }

     /**

      * Appends an additional coverage effect to the coverage computation.

      */

     const GrEffectRef* addCoverageEffect(const GrEffectRef* effect, int attr0 = -1, int attr1 = -1) {

         SkASSERT(NULL != effect);

         if (!(*effect)->willUseInputColor()) {

             fCoverageStages.reset();

         }

         SkNEW_APPEND_TO_TARRAY(&fCoverageStages, GrEffectStage, (effect, attr0, attr1));

         return effect;

     }

     /**

      * Helpers for adding color or coverage effects that sample a texture. The matrix is applied

      * to the src space position to compute texture coordinates.

      */

     void addColorTextureEffect(GrTexture* texture, const SkMatrix& matrix);

     void addCoverageTextureEffect(GrTexture* texture, const SkMatrix& matrix);

     void addColorTextureEffect(GrTexture* texture,

                                const SkMatrix& matrix,

                                const GrTextureParams& params);

     void addCoverageTextureEffect(GrTexture* texture,

                                   const SkMatrix& matrix,

                                   const GrTextureParams& params);

     int numColorStages() const { return fColorStages.count(); }

     int numCoverageStages() const { return fCoverageStages.count(); }

     int numTotalStages() const { return this->numColorStages() + this->numCoverageStages(); }

     const GrEffectStage& getColorStage(int s) const { return fColorStages[s]; }

     const GrEffectStage& getCoverageStage(int s) const { return fCoverageStages[s]; }

     GrPaint& operator=(const GrPaint& paint) {

         fSrcBlendCoeff = paint.fSrcBlendCoeff;

         fDstBlendCoeff = paint.fDstBlendCoeff;

         fAntiAlias = paint.fAntiAlias;

         fDither = paint.fDither;

         fColor = paint.fColor;

         fCoverage = paint.fCoverage;

         fColorStages = paint.fColorStages;

         fCoverageStages = paint.fCoverageStages;

         return *this;

     }

     /**

      * Resets the paint to the defaults.

      */

     void reset() {

         this->resetBlend();

         this->resetOptions();

         this->resetColor();

         this->resetCoverage();

         this->resetStages();

     }

     /**

      * Determines whether the drawing with this paint is opaque with respect to both color blending

      * and fractional coverage. It does not consider whether AA has been enabled on the paint or

      * not. Depending upon whether multisampling or coverage-based AA is in use, AA may make the

      * result only apply to the interior of primitives.

      *

      */

     bool isOpaque() const;

     /**

      * Returns true if isOpaque would return true and the paint represents a solid constant color

      * draw. If the result is true, constantColor will be updated to contain the constant color.

      */

     bool isOpaqueAndConstantColor(GrColor* constantColor) const;

 private:

     /**

      * Helper for isOpaque and isOpaqueAndConstantColor.

      */

     bool getOpaqueAndKnownColor(GrColor* solidColor, uint32_t* solidColorKnownComponents) const;

     /**

      * Called when the source coord system from which geometry is rendered changes. It ensures that

      * the local coordinates seen by effects remains unchanged. oldToNew gives the transformation

      * from the previous coord system to the new coord system.

      */

     void localCoordChange(const SkMatrix& oldToNew) {

         for (int i = 0; i < fColorStages.count(); ++i) {

             fColorStages[i].localCoordChange(oldToNew);

         }

         for (int i = 0; i < fCoverageStages.count(); ++i) {

             fCoverageStages[i].localCoordChange(oldToNew);

         }

     }

     bool localCoordChangeInverse(const SkMatrix& newToOld) {

         SkMatrix oldToNew;

         bool computed = false;

         for (int i = 0; i < fColorStages.count(); ++i) {

             if (!computed && !newToOld.invert(&oldToNew)) {

                 return false;

             } else {

                 computed = true;

             }

             fColorStages[i].localCoordChange(oldToNew);

         }

         for (int i = 0; i < fCoverageStages.count(); ++i) {

             if (!computed && !newToOld.invert(&oldToNew)) {

                 return false;

             } else {

                 computed = true;

             }

             fCoverageStages[i].localCoordChange(oldToNew);

         }

         return true;

     }

     friend class GrContext; // To access above two functions

     SkSTArray<4, GrEffectStage> fColorStages;

     SkSTArray<2, GrEffectStage> fCoverageStages;

     GrBlendCoeff                fSrcBlendCoeff;

     GrBlendCoeff                fDstBlendCoeff;

     bool                        fAntiAlias;

     bool                        fDither;

     GrColor                     fColor;

     uint8_t                     fCoverage;

     void resetBlend() {

         fSrcBlendCoeff = kOne_GrBlendCoeff;

         fDstBlendCoeff = kZero_GrBlendCoeff;

     }

     void resetOptions() {

         fAntiAlias = false;

         fDither = false;

     }

     void resetColor() {

         fColor = GrColorPackRGBA(0xff, 0xff, 0xff, 0xff);

     }

     void resetCoverage() {

         fCoverage = 0xff;

     }

     void resetStages() {

         fColorStages.reset();

         fCoverageStages.reset();

     }

 };

 #endif