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      1 /*
      2  * Copyright 2014 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef GrPathRendering_DEFINED
      9 #define GrPathRendering_DEFINED
     10 
     11 #include "SkPath.h"
     12 #include "GrPathRange.h"
     13 
     14 class SkStrokeRec;
     15 class SkDescriptor;
     16 class SkTypeface;
     17 class GrPath;
     18 class GrGpu;
     19 class GrStencilSettings;
     20 
     21 /**
     22  * Abstract class wrapping HW path rendering API.
     23  *
     24  * The subclasses of this class use the possible HW API to render paths (as opposed to path
     25  * rendering implemented in Skia on top of a "3d" HW API).
     26  * The subclasses hold the global state needed to render paths, including shadow of the global HW
     27  * API state. Similar to GrGpu.
     28  *
     29  * It is expected that the lifetimes of GrGpuXX and GrXXPathRendering are the same. The call context
     30  * interface (eg.  * the concrete instance of GrGpu subclass) should be provided to the instance
     31  * during construction.
     32  */
     33 class GrPathRendering {
     34 public:
     35     virtual ~GrPathRendering() { }
     36 
     37     typedef GrPathRange::PathIndexType PathIndexType;
     38 
     39     enum PathTransformType {
     40         kNone_PathTransformType,        //!< []
     41         kTranslateX_PathTransformType,  //!< [kMTransX]
     42         kTranslateY_PathTransformType,  //!< [kMTransY]
     43         kTranslate_PathTransformType,   //!< [kMTransX, kMTransY]
     44         kAffine_PathTransformType,      //!< [kMScaleX, kMSkewX, kMTransX, kMSkewY, kMScaleY, kMTransY]
     45 
     46         kLast_PathTransformType = kAffine_PathTransformType
     47     };
     48 
     49     static inline int PathTransformSize(PathTransformType type) {
     50         switch (type) {
     51             case kNone_PathTransformType:
     52                 return 0;
     53             case kTranslateX_PathTransformType:
     54             case kTranslateY_PathTransformType:
     55                 return 1;
     56             case kTranslate_PathTransformType:
     57                 return 2;
     58             case kAffine_PathTransformType:
     59                 return 6;
     60 
     61             default:
     62                 SkFAIL("Unknown path transform type");
     63                 return 0;
     64         }
     65     }
     66 
     67     // No native support for inverse at this time
     68     enum FillType {
     69         /** Specifies that "inside" is computed by a non-zero sum of signed
     70             edge crossings
     71         */
     72         kWinding_FillType,
     73         /** Specifies that "inside" is computed by an odd number of edge
     74             crossings
     75         */
     76         kEvenOdd_FillType,
     77     };
     78 
     79     /**
     80      * Creates a new gpu path, based on the specified path and stroke and returns it.
     81      * The caller owns a ref on the returned path which must be balanced by a call to unref.
     82      *
     83      * @param skPath the path geometry.
     84      * @param stroke the path stroke.
     85      * @return a new path.
     86      */
     87     virtual GrPath* createPath(const SkPath&, const SkStrokeRec&) = 0;
     88 
     89     /**
     90      * Creates a range of gpu paths with a common stroke. The caller owns a ref on the
     91      * returned path range which must be balanced by a call to unref.
     92      *
     93      * @param PathGenerator class that generates SkPath objects for each path in the range.
     94      * @param SkStrokeRec   the common stroke applied to each path in the range.
     95      * @return a new path range.
     96      */
     97     virtual GrPathRange* createPathRange(GrPathRange::PathGenerator*, const SkStrokeRec&) = 0;
     98 
     99     /**
    100      * Creates a range of glyph paths, indexed by glyph id. The glyphs will have an
    101      * inverted y-direction in order to match the raw font path data. The caller owns
    102      * a ref on the returned path range which must be balanced by a call to unref.
    103      *
    104      * @param SkTypeface   Typeface that defines the glyphs.
    105      *                     If null, the default typeface will be used.
    106      *
    107      * @param SkDescriptor Additional font configuration that specifies the font's size,
    108      *                     stroke, and other flags. This will generally come from an
    109      *                     SkGlyphCache.
    110      *
    111      *                     It is recommended to leave this value null when possible, in
    112      *                     which case the glyphs will be loaded directly from the font's
    113      *                     raw path data and sized at SkPaint::kCanonicalTextSizeForPaths.
    114      *                     This will result in less memory usage and more efficient paths.
    115      *
    116      *                     If non-null, the glyph paths will match the font descriptor,
    117      *                     including with the stroke information baked directly into
    118      *                     the outlines.
    119      *
    120      * @param SkStrokeRec  Common stroke that the GPU will apply to every path. Note that
    121      *                     if the glyph outlines contain baked-in strokes from the font
    122      *                     descriptor, the GPU stroke will be applied on top of those
    123      *                     outlines.
    124      *
    125      * @return a new path range populated with glyphs.
    126      */
    127     virtual GrPathRange* createGlyphs(const SkTypeface*, const SkDescriptor*, const SkStrokeRec&) = 0;
    128 
    129     virtual void stencilPath(const GrPath*, const GrStencilSettings&) = 0;
    130     virtual void drawPath(const GrPath*, const GrStencilSettings&) = 0;
    131     virtual void drawPaths(const GrPathRange*, const void* indices, PathIndexType,
    132                            const float transformValues[], PathTransformType, int count,
    133                            const GrStencilSettings&) = 0;
    134 protected:
    135     GrPathRendering() { }
    136 
    137 private:
    138     GrPathRendering& operator=(const GrPathRendering&);
    139 };
    140 
    141 #endif
    142