231 lines
7.8 KiB
C++
231 lines
7.8 KiB
C++
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/*
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* Copyright 2011 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef GrPaint_DEFINED
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#define GrPaint_DEFINED
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#include "GrColor.h"
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#include "GrProcessorStage.h"
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#include "SkXfermode.h"
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/**
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* The paint describes how color and coverage are computed at each pixel by GrContext draw
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* functions and the how color is blended with the destination pixel.
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*
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* The paint allows installation of custom color and coverage stages. New types of stages are
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* created by subclassing GrProcessor.
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*
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* The primitive color computation starts with the color specified by setColor(). This color is the
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* input to the first color stage. Each color stage feeds its output to the next color stage. The
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* final color stage's output color is input to the color filter specified by
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* setXfermodeColorFilter which produces the final source color, S.
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*
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* Fractional pixel coverage follows a similar flow. The coverage is initially the value specified
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* by setCoverage(). This is input to the first coverage stage. Coverage stages are chained
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* together in the same manner as color stages. The output of the last stage is modulated by any
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* fractional coverage produced by anti-aliasing. This last step produces the final coverage, C.
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*
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* setBlendFunc() specifies blending coefficients for S (described above) and D, the initial value
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* of the destination pixel, labeled Bs and Bd respectively. The final value of the destination
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* pixel is then D' = (1-C)*D + C*(Bd*D + Bs*S).
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*
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* Note that the coverage is applied after the blend. This is why they are computed as distinct
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* values.
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*
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* TODO: Encapsulate setXfermodeColorFilter in a GrProcessor and remove from GrPaint.
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*/
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class GrPaint {
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public:
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GrPaint() { this->reset(); }
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GrPaint(const GrPaint& paint) { *this = paint; }
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~GrPaint() {}
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/**
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* Sets the blending coefficients to use to blend the final primitive color with the
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* destination color. Defaults to kOne for src and kZero for dst (i.e. src mode).
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*/
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void setBlendFunc(GrBlendCoeff srcCoeff, GrBlendCoeff dstCoeff) {
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fSrcBlendCoeff = srcCoeff;
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fDstBlendCoeff = dstCoeff;
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}
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GrBlendCoeff getSrcBlendCoeff() const { return fSrcBlendCoeff; }
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GrBlendCoeff getDstBlendCoeff() const { return fDstBlendCoeff; }
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/**
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* The initial color of the drawn primitive. Defaults to solid white.
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*/
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void setColor(GrColor color) { fColor = color; }
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GrColor getColor() const { return fColor; }
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/**
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* Should primitives be anti-aliased or not. Defaults to false.
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*/
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void setAntiAlias(bool aa) { fAntiAlias = aa; }
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bool isAntiAlias() const { return fAntiAlias; }
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/**
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* Should dithering be applied. Defaults to false.
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*/
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void setDither(bool dither) { fDither = dither; }
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bool isDither() const { return fDither; }
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/**
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* Appends an additional color processor to the color computation.
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*/
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const GrFragmentProcessor* addColorProcessor(const GrFragmentProcessor* fp) {
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SkASSERT(fp);
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SkNEW_APPEND_TO_TARRAY(&fColorStages, GrFragmentStage, (fp));
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return fp;
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}
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/**
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* Appends an additional coverage processor to the coverage computation.
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*/
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const GrFragmentProcessor* addCoverageProcessor(const GrFragmentProcessor* fp) {
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SkASSERT(fp);
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SkNEW_APPEND_TO_TARRAY(&fCoverageStages, GrFragmentStage, (fp));
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return fp;
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}
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/**
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* Helpers for adding color or coverage effects that sample a texture. The matrix is applied
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* to the src space position to compute texture coordinates.
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*/
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void addColorTextureProcessor(GrTexture*, const SkMatrix&);
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void addCoverageTextureProcessor(GrTexture*, const SkMatrix&);
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void addColorTextureProcessor(GrTexture*, const SkMatrix&, const GrTextureParams&);
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void addCoverageTextureProcessor(GrTexture*, const SkMatrix&, const GrTextureParams&);
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int numColorStages() const { return fColorStages.count(); }
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int numCoverageStages() const { return fCoverageStages.count(); }
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int numTotalStages() const { return this->numColorStages() + this->numCoverageStages(); }
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const GrFragmentStage& getColorStage(int s) const { return fColorStages[s]; }
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const GrFragmentStage& getCoverageStage(int s) const { return fCoverageStages[s]; }
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GrPaint& operator=(const GrPaint& paint) {
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fSrcBlendCoeff = paint.fSrcBlendCoeff;
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fDstBlendCoeff = paint.fDstBlendCoeff;
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fAntiAlias = paint.fAntiAlias;
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fDither = paint.fDither;
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fColor = paint.fColor;
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fColorStages = paint.fColorStages;
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fCoverageStages = paint.fCoverageStages;
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return *this;
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}
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/**
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* Resets the paint to the defaults.
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*/
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void reset() {
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this->resetBlend();
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this->resetOptions();
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this->resetColor();
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this->resetStages();
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}
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/**
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* Determines whether the drawing with this paint is opaque with respect to both color blending
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* and fractional coverage. It does not consider whether AA has been enabled on the paint or
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* not. Depending upon whether multisampling or coverage-based AA is in use, AA may make the
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* result only apply to the interior of primitives.
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*
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*/
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bool isOpaque() const;
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/**
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* Returns true if isOpaque would return true and the paint represents a solid constant color
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* draw. If the result is true, constantColor will be updated to contain the constant color.
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*/
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bool isOpaqueAndConstantColor(GrColor* constantColor) const;
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private:
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/**
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* Helper for isOpaque and isOpaqueAndConstantColor.
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*/
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bool getOpaqueAndKnownColor(GrColor* solidColor, uint32_t* solidColorKnownComponents) const;
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/**
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* Called when the source coord system from which geometry is rendered changes. It ensures that
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* the local coordinates seen by effects remains unchanged. oldToNew gives the transformation
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* from the previous coord system to the new coord system.
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*/
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void localCoordChange(const SkMatrix& oldToNew) {
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for (int i = 0; i < fColorStages.count(); ++i) {
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fColorStages[i].localCoordChange(oldToNew);
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}
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for (int i = 0; i < fCoverageStages.count(); ++i) {
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fCoverageStages[i].localCoordChange(oldToNew);
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}
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}
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bool localCoordChangeInverse(const SkMatrix& newToOld) {
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SkMatrix oldToNew;
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bool computed = false;
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for (int i = 0; i < fColorStages.count(); ++i) {
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if (!computed && !newToOld.invert(&oldToNew)) {
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return false;
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} else {
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computed = true;
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}
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fColorStages[i].localCoordChange(oldToNew);
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}
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for (int i = 0; i < fCoverageStages.count(); ++i) {
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if (!computed && !newToOld.invert(&oldToNew)) {
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return false;
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} else {
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computed = true;
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}
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fCoverageStages[i].localCoordChange(oldToNew);
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}
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return true;
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}
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friend class GrContext; // To access above two functions
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friend class GrStencilAndCoverTextContext; // To access above two functions
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SkSTArray<4, GrFragmentStage> fColorStages;
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SkSTArray<2, GrFragmentStage> fCoverageStages;
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GrBlendCoeff fSrcBlendCoeff;
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GrBlendCoeff fDstBlendCoeff;
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bool fAntiAlias;
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bool fDither;
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GrColor fColor;
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void resetBlend() {
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fSrcBlendCoeff = kOne_GrBlendCoeff;
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fDstBlendCoeff = kZero_GrBlendCoeff;
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}
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void resetOptions() {
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fAntiAlias = false;
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fDither = false;
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}
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void resetColor() {
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fColor = GrColorPackRGBA(0xff, 0xff, 0xff, 0xff);
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}
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void resetStages() {
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fColorStages.reset();
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fCoverageStages.reset();
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}
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};
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#endif
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