gecko-dev/gfx/2d/HelpersSkia.h

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#ifndef MOZILLA_GFX_HELPERSSKIA_H_
#define MOZILLA_GFX_HELPERSSKIA_H_

#include "2D.h"
#include "skia/SkCanvas.h"
#include "skia/SkDashPathEffect.h"
#include "mozilla/Assertions.h"

namespace mozilla {
namespace gfx {

static inline SkBitmap::Config
GfxFormatToSkiaConfig(SurfaceFormat format)
{
  switch (format)
  {
    case FORMAT_B8G8R8A8:
      return SkBitmap::kARGB_8888_Config;
    case FORMAT_B8G8R8X8:
      // We probably need to do something here.
      return SkBitmap::kARGB_8888_Config;
    case FORMAT_R5G6B5:
      return SkBitmap::kRGB_565_Config;
    case FORMAT_A8:
      return SkBitmap::kA8_Config;

  }

  return SkBitmap::kARGB_8888_Config;
}

static inline void
GfxMatrixToSkiaMatrix(const Matrix& mat, SkMatrix& retval)
{
    retval.setAll(SkFloatToScalar(mat._11), SkFloatToScalar(mat._21), SkFloatToScalar(mat._31),
                  SkFloatToScalar(mat._12), SkFloatToScalar(mat._22), SkFloatToScalar(mat._32),
                  0, 0, SK_Scalar1);
}

static inline SkPaint::Cap
CapStyleToSkiaCap(CapStyle aCap)
{
  switch (aCap)
  {
    case CAP_BUTT:
      return SkPaint::kButt_Cap;
    case CAP_ROUND:
      return SkPaint::kRound_Cap;
    case CAP_SQUARE:
      return SkPaint::kSquare_Cap;
  }
  return SkPaint::kDefault_Cap;
}

static inline SkPaint::Join
JoinStyleToSkiaJoin(JoinStyle aJoin)
{
  switch (aJoin)
  {
    case JOIN_BEVEL:
      return SkPaint::kBevel_Join;
    case JOIN_ROUND:
      return SkPaint::kRound_Join;
    case JOIN_MITER:
    case JOIN_MITER_OR_BEVEL:
      return SkPaint::kMiter_Join;
  }
  return SkPaint::kDefault_Join;
}

static inline bool
StrokeOptionsToPaint(SkPaint& aPaint, const StrokeOptions &aOptions)
{
  // Skia rendewrs 0 width strokes with a width of 1 (and in black),
  // so we should just skip the draw call entirely.
  if (!aOptions.mLineWidth) {
    return false;
  }
  aPaint.setStrokeWidth(SkFloatToScalar(aOptions.mLineWidth));
  aPaint.setStrokeMiter(SkFloatToScalar(aOptions.mMiterLimit));
  aPaint.setStrokeCap(CapStyleToSkiaCap(aOptions.mLineCap));
  aPaint.setStrokeJoin(JoinStyleToSkiaJoin(aOptions.mLineJoin));

  if (aOptions.mDashLength > 0) {
    // Skia only supports dash arrays that are multiples of 2.
    uint32_t dashCount;

    if (aOptions.mDashLength % 2 == 0) {
      dashCount = aOptions.mDashLength;
    } else {
      dashCount = aOptions.mDashLength * 2;
    }

    std::vector<SkScalar> pattern;
    pattern.resize(dashCount);

    for (uint32_t i = 0; i < dashCount; i++) {
      pattern[i] = SkFloatToScalar(aOptions.mDashPattern[i % aOptions.mDashLength]);
    }

    SkDashPathEffect* dash = new SkDashPathEffect(&pattern.front(),
                                                  dashCount, 
                                                  SkFloatToScalar(aOptions.mDashOffset));
    SkSafeUnref(aPaint.setPathEffect(dash));
  }

  aPaint.setStyle(SkPaint::kStroke_Style);
  return true;
}

}
}

#endif /* MOZILLA_GFX_HELPERSSKIA_H_ */