src/gpu/text/GrTextBlob.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 GrTextBlob_DEFINED
#define GrTextBlob_DEFINED

#include "include/core/SkPoint3.h"
#include "src/core/SkDescriptor.h"
#include "src/core/SkMaskFilterBase.h"
#include "src/core/SkOpts.h"
#include "src/core/SkRectPriv.h"
#include "src/core/SkStrikeSpec.h"
#include "src/gpu/GrColor.h"
#include "src/gpu/GrDrawOpAtlas.h"

#include <limits>

class GrAtlasManager;
class GrAtlasTextOp;
class GrGlyph;
class GrStrikeCache;
class GrTextContext;

class SkSurfaceProps;
class SkTextBlob;
class SkTextBlobRunIterator;


// A GrTextBlob contains a fully processed SkTextBlob, suitable for nearly immediate drawing
// on the GPU.  These are initially created with valid positions and colors, but invalid
// texture coordinates.
//
// A GrTextBlob contains a number of SubRuns that are created in the blob's arena. Each SubRun
// tracks its own GrGlyph* and vertex data. The memory is organized in the arena in the following
// way so that the pointers for the GrGlyph* and vertex data are known before creating the SubRun.
//
//  GrGlyph*... | vertexData... | SubRun | GrGlyph*... | vertexData... | SubRun  etc.
//
// In these classes, I'm trying to follow the convention about matrices and origins.
// * draw Matrix|Origin    - describes the current draw command.
// * initial Matrix|Origin - describes the matrix and origin the GrTextBlob was created with.
// * current Matrix|Origin - describes the matrix and origin that are currently in the SubRun's
//                           vertex data.
//
// When handling repeated drawing using the same GrTextBlob initial data are compared to drawing
// data to see if this blob can service this drawing. If it can, but small changes are needed to
// the vertex data, the current data of the SubRuns is adjusted to conform to the drawing data
// from the op using the VertexRegenerator.
//
class GrTextBlob final : public SkNVRefCnt<GrTextBlob>, public SkGlyphRunPainterInterface {
public:
    class SubRun;
    class VertexRegenerator;

    enum SubRunType {
        kDirectMask,
        kTransformedMask,
        kTransformedPath,
        kTransformedSDFT
    };

    struct Key {
        Key();
        uint32_t fUniqueID;
        // Color may affect the gamma of the mask we generate, but in a fairly limited way.
        // Each color is assigned to on of a fixed number of buckets based on its
        // luminance. For each luminance bucket there is a "canonical color" that
        // represents the bucket.  This functionality is currently only supported for A8
        SkColor fCanonicalColor;
        SkPaint::Style fStyle;
        SkPixelGeometry fPixelGeometry;
        bool fHasBlur;
        uint32_t fScalerContextFlags;

        bool operator==(const Key& other) const;
    };

    // Any glyphs that can't be rendered with the base or override descriptor
    // are rendered as paths
    struct PathGlyph {
        PathGlyph(const SkPath& path, SkPoint origin);
        SkPath fPath;
        SkPoint fOrigin;
    };

    SK_DECLARE_INTERNAL_LLIST_INTERFACE(GrTextBlob);

    // Change memory management to handle the data after GrTextBlob, but in the same allocation
    // of memory. Only allow placement new.
    void operator delete(void* p);
    void* operator new(size_t);
    void* operator new(size_t, void* p);

    ~GrTextBlob() override;

    // Make an empty GrTextBlob, with all the invariants set to make the right decisions when
    // adding SubRuns.
    static sk_sp<GrTextBlob> Make(const SkGlyphRunList& glyphRunList,
                                  GrStrikeCache* strikeCache,
                                  const SkMatrix& drawMatrix,
                                  GrColor color,
                                  bool forceWForDistanceFields);

    // Key manipulation functions
    void setupKey(const GrTextBlob::Key& key,
                  const SkMaskFilterBase::BlurRec& blurRec,
                  const SkPaint& paint);
    static const Key& GetKey(const GrTextBlob& blob);
    static uint32_t Hash(const Key& key);

    bool hasDistanceField() const;
    bool hasBitmap() const;
    bool hasPerspective() const;

    void setHasDistanceField();
    void setHasBitmap();
    void setMinAndMaxScale(SkScalar scaledMin, SkScalar scaledMax);

    static size_t GetVertexStride(GrMaskFormat maskFormat, bool hasWCoord);

    bool mustRegenerate(const SkPaint&, bool, const SkMaskFilterBase::BlurRec& blurRec,
                        const SkMatrix& drawMatrix, SkPoint drawOrigin);

    void flush(GrTextTarget*, const SkSurfaceProps& props,
               const SkPaint& paint, const SkPMColor4f& filteredColor, const GrClip& clip,
               const SkMatrix& drawMatrix, SkPoint drawOrigin);

    void computeSubRunBounds(SkRect* outBounds, const SubRun& subRun,
                             const SkMatrix& drawMatrix, SkPoint drawOrigin,
                             bool needsGlyphTransform);

    // Normal text mask, SDFT, or color.
    struct Mask2DVertex {
        SkPoint devicePos;
        GrColor color;
        SkIPoint16 atlasPos;
    };
    struct ARGB2DVertex {
        SkPoint devicePos;
        SkIPoint16 atlasPos;
    };

    // Perspective SDFT or SDFT forced to 3D or perspective color.
    struct SDFT3DVertex {
        SkPoint3 devicePos;
        GrColor color;
        SkIPoint16 atlasPos;
    };
    struct ARGB3DVertex {
        SkPoint3 devicePos;
        SkIPoint16 atlasPos;
    };

    static const int kVerticesPerGlyph = 4;

    const Key& key() const;
    size_t size() const;

    // Internal test methods
    std::unique_ptr<GrDrawOp> test_makeOp(int glyphCount, const SkMatrix& drawMatrix,
                                          SkPoint drawOrigin, const SkPaint& paint,
                                          const SkPMColor4f& filteredColor, const SkSurfaceProps&,
                                          GrTextTarget*);

    bool hasW(SubRunType type) const;

    SubRun* makeSubRun(SubRunType type,
                       const SkZip<SkGlyphVariant, SkPoint>& drawables,
                       const SkStrikeSpec& strikeSpec,
                       GrMaskFormat format);

    void addSingleMaskFormat(
            SubRunType type,
            const SkZip<SkGlyphVariant, SkPoint>& drawables,
            const SkStrikeSpec& strikeSpec,
            GrMaskFormat format);

    void addMultiMaskFormat(
            SubRunType type,
            const SkZip<SkGlyphVariant, SkPoint>& drawables,
            const SkStrikeSpec& strikeSpec);

    void addSDFT(const SkZip<SkGlyphVariant, SkPoint>& drawables,
                 const SkStrikeSpec& strikeSpec,
                 const SkFont& runFont,
                 SkScalar minScale,
                 SkScalar maxScale);

private:
    enum TextType {
        kHasDistanceField_TextType = 0x1,
        kHasBitmap_TextType = 0x2,
    };

    struct StrokeInfo {
        SkScalar fFrameWidth;
        SkScalar fMiterLimit;
        SkPaint::Join fJoin;
    };

    GrTextBlob(size_t allocSize,
               GrStrikeCache* strikeCache,
               const SkMatrix& drawMatrix,
               SkPoint origin,
               GrColor color,
               SkColor initialLuminance,
               bool forceWForDistanceFields);

    void insertSubRun(SubRun* subRun);

    std::unique_ptr<GrAtlasTextOp> makeOp(SubRun& info, int glyphCount, const SkMatrix& drawMatrix,
                                          SkPoint drawOrigin, const SkIRect& clipRect,
                                          const SkPaint& paint, const SkPMColor4f& filteredColor,
                                          const SkSurfaceProps&, GrTextTarget*);

    // Methods to satisfy SkGlyphRunPainterInterface
    void processDeviceMasks(const SkZip<SkGlyphVariant, SkPoint>& drawables,
                            const SkStrikeSpec& strikeSpec) override;
    void processSourcePaths(const SkZip<SkGlyphVariant, SkPoint>& drawables,
                            const SkFont& runFont,
                            const SkStrikeSpec& strikeSpec) override;
    void processSourceSDFT(const SkZip<SkGlyphVariant, SkPoint>& drawables,
                           const SkStrikeSpec& strikeSpec,
                           const SkFont& runFont,
                           SkScalar minScale,
                           SkScalar maxScale) override;
    void processSourceMasks(const SkZip<SkGlyphVariant, SkPoint>& drawables,
                            const SkStrikeSpec& strikeSpec) override;

    // Overall size of this struct plus vertices and glyphs at the end.
    const size_t fSize;

    // Lifetime: The GrStrikeCache is owned by and has the same lifetime as the GrRecordingContext.
    // The GrRecordingContext also owns the GrTextBlob cache which owns this GrTextBlob.
    GrStrikeCache* const fStrikeCache;

    // The initial view matrix and its inverse. This is used for moving additional draws of this
    // same text blob. We record the initial view matrix and initial offsets(x,y), because we
    // record vertex bounds relative to these numbers.  When blobs are reused with new matrices,
    // we need to return to source space so we can update the vertex bounds appropriately.
    const SkMatrix fInitialMatrix;
    const SkMatrix fInitialMatrixInverse;

    // Initial position of this blob. Used for calculating position differences when reusing this
    // blob.
    const SkPoint fInitialOrigin;

    // From the distance field options to force distance fields to have a W coordinate.
    const bool fForceWForDistanceFields;

    // The color of the text to draw for solid colors.
    const GrColor fColor;
    const SkColor fInitialLuminance;

    SkMaskFilterBase::BlurRec fBlurRec;
    StrokeInfo fStrokeInfo;
    Key fKey;

    // We can reuse distance field text, but only if the new view matrix would not result in
    // a mip change.  Because there can be multiple runs in a blob, we track the overall
    // maximum minimum scale, and minimum maximum scale, we can support before we need to regen
    SkScalar fMaxMinScale{-SK_ScalarMax};
    SkScalar fMinMaxScale{SK_ScalarMax};

    uint8_t fTextType{0};

    SubRun* fFirstSubRun{nullptr};
    SubRun* fLastSubRun{nullptr};
    SkArenaAlloc fAlloc;
};

/**
 * Used to produce vertices for a subrun of a blob. The vertices are cached in the blob itself.
 * This is invoked each time a sub run is drawn. It regenerates the vertex data as required either
 * because of changes to the atlas or because of different draw parameters (e.g. color change). In
 * rare cases the draw may have to interrupted and flushed in the middle of the sub run in order to
 * free up atlas space. Thus, this generator is stateful and should be invoked in a loop until the
 * entire sub run has been completed.
 */
class GrTextBlob::VertexRegenerator {
public:
    /**
     * Consecutive VertexRegenerators often use the same SkGlyphCache. If the same instance of
     * SkAutoGlyphCache is reused then it can save the cost of multiple detach/attach operations of
     * SkGlyphCache.
     */
    VertexRegenerator(GrResourceProvider*, GrTextBlob::SubRun* subRun,
                      GrDeferredUploadTarget*, GrAtlasManager*);

    // Return {success, number of glyphs regenerated}
    std::tuple<bool, int> regenerate(int begin, int end);

private:
    // Return {success, number of glyphs regenerated}
    std::tuple<bool, int> updateTextureCoordinates(int begin, int end);

    GrResourceProvider* fResourceProvider;
    GrDeferredUploadTarget* fUploadTarget;
    GrAtlasManager* fFullAtlasManager;
    SkTLazy<SkBulkGlyphMetricsAndImages> fMetricsAndImages;
    SubRun* fSubRun;
};

// -- GrTextBlob::SubRun ---------------------------------------------------------------------------
// Hold data to draw the different types of sub run. SubRuns are produced knowing all the
// glyphs that are included in them.
class GrTextBlob::SubRun {
public:
    // SubRun for masks
    SubRun(SubRunType type,
           GrTextBlob* textBlob,
           const SkStrikeSpec& strikeSpec,
           GrMaskFormat format,
           const SkSpan<GrGlyph*>& glyphs, const SkSpan<char>& vertexData,
           sk_sp<GrTextStrike>&& grStrike);

    // SubRun for paths
    SubRun(GrTextBlob* textBlob, const SkStrikeSpec& strikeSpec);

    void appendGlyphs(const SkZip<SkGlyphVariant, SkPoint>& drawables);

    // TODO when this object is more internal, drop the privacy
    void resetBulkUseToken();
    GrDrawOpAtlas::BulkUseTokenUpdater* bulkUseToken();
    void setStrike(sk_sp<GrTextStrike> strike);
    GrTextStrike* strike() const;

    GrMaskFormat maskFormat() const;

    size_t vertexStride() const;
    size_t colorOffset() const;
    size_t texCoordOffset() const;
    char* quadStart(size_t index) const;
    size_t quadOffset(size_t index) const;

    const SkRect& vertexBounds() const;
    void joinGlyphBounds(const SkRect& glyphBounds);

    bool drawAsDistanceFields() const;
    bool drawAsPaths() const;
    bool needsTransform() const;
    bool needsPadding() const;

    void translateVerticesIfNeeded(const SkMatrix& drawMatrix, SkPoint drawOrigin);
    void updateVerticesColorIfNeeded(GrColor newColor);
    void updateTexCoords(int begin, int end);

    // df properties
    void setUseLCDText(bool useLCDText);
    bool hasUseLCDText() const;
    void setAntiAliased(bool antiAliased);
    bool isAntiAliased() const;

    const SkStrikeSpec& strikeSpec() const;

    SubRun* fNextSubRun{nullptr};
    const SubRunType fType;
    GrTextBlob* const fBlob;
    const GrMaskFormat fMaskFormat;
    const SkSpan<GrGlyph*> fGlyphs;
    const SkSpan<char> fVertexData;
    const SkStrikeSpec fStrikeSpec;
    sk_sp<GrTextStrike> fStrike;
    struct {
        bool useLCDText:1;
        bool antiAliased:1;
    } fFlags{false, false};
    GrDrawOpAtlas::BulkUseTokenUpdater fBulkUseToken;
    SkRect fVertexBounds = SkRectPriv::MakeLargestInverted();
    uint64_t fAtlasGeneration{GrDrawOpAtlas::kInvalidAtlasGeneration};
    GrColor fCurrentColor;
    SkPoint fCurrentOrigin;
    SkMatrix fCurrentMatrix;
    std::vector<PathGlyph> fPaths;

private:
    bool hasW() const;

};  // SubRun

#endif  // GrTextBlob_DEFINED