C API: add sk_xfermode.h, impl, test

src/c/sk_paint.cpp

Index: src/c/sk_paint.cpp
diff --git a/src/c/sk_paint.cpp b/src/c/sk_paint.cpp
index e71285d4d5ca16924051fedc5750d28d558fc1be..edd672c01a9f248453427c76ec8b7162c9cb464c 100644
--- a/src/c/sk_paint.cpp
+++ b/src/c/sk_paint.cpp
@@ -132,4 +132,42 @@ void sk_paint_set_stroke_join(sk_paint_t* cpaint, sk_stroke_join_t cjoin) {
     }
 }
 
+static SkXfermode::Mode convert_skxfermodemode(sk_xfermode_mode_t mode) {
+    switch (mode) {
+        case CLEAR_SK_XFERMODE_MODE:      return SkXfermode::kClear_Mode;
+        case SRC_SK_XFERMODE_MODE:        return SkXfermode::kSrc_Mode;
+        case DST_SK_XFERMODE_MODE:        return SkXfermode::kDst_Mode;
+        case SRCOVER_SK_XFERMODE_MODE:    return SkXfermode::kSrcOver_Mode;
+        case DSTOVER_SK_XFERMODE_MODE:    return SkXfermode::kDstOver_Mode;
+        case SRCIN_SK_XFERMODE_MODE:      return SkXfermode::kSrcIn_Mode;
+        case DSTIN_SK_XFERMODE_MODE:      return SkXfermode::kDstIn_Mode;
+        case SRCOUT_SK_XFERMODE_MODE:     return SkXfermode::kSrcOut_Mode;
+        case DSTOUT_SK_XFERMODE_MODE:     return SkXfermode::kDstOut_Mode;
+        case SRCATOP_SK_XFERMODE_MODE:    return SkXfermode::kSrcATop_Mode;
+        case DSTATOP_SK_XFERMODE_MODE:    return SkXfermode::kDstATop_Mode;
+        case XOR_SK_XFERMODE_MODE:        return SkXfermode::kXor_Mode;
+        case PLUS_SK_XFERMODE_MODE:       return SkXfermode::kPlus_Mode;
+        case MODULATE_SK_XFERMODE_MODE:   return SkXfermode::kModulate_Mode;
+        case SCREEN_SK_XFERMODE_MODE:     return SkXfermode::kScreen_Mode;
+        case OVERLAY_SK_XFERMODE_MODE:    return SkXfermode::kOverlay_Mode;
+        case DARKEN_SK_XFERMODE_MODE:     return SkXfermode::kDarken_Mode;
+        case LIGHTEN_SK_XFERMODE_MODE:    return SkXfermode::kLighten_Mode;
+        case COLORDODGE_SK_XFERMODE_MODE: return SkXfermode::kColorDodge_Mode;
+        case COLORBURN_SK_XFERMODE_MODE:  return SkXfermode::kColorBurn_Mode;
+        case HARDLIGHT_SK_XFERMODE_MODE:  return SkXfermode::kHardLight_Mode;
+        case SOFTLIGHT_SK_XFERMODE_MODE:  return SkXfermode::kSoftLight_Mode;
+        case DIFFERENCE_SK_XFERMODE_MODE: return SkXfermode::kDifference_Mode;
+        case EXCLUSION_SK_XFERMODE_MODE:  return SkXfermode::kExclusion_Mode;
+        case MULTIPLY_SK_XFERMODE_MODE:   return SkXfermode::kMultiply_Mode;
+        case HUE_SK_XFERMODE_MODE:        return SkXfermode::kHue_Mode;
+        case SATURATION_SK_XFERMODE_MODE: return SkXfermode::kSaturation_Mode;
+        case COLOR_SK_XFERMODE_MODE:      return SkXfermode::kColor_Mode;
+        case LUMINOSITY_SK_XFERMODE_MODE: return SkXfermode::kLuminosity_Mode;
+        default:                          return SkXfermode::kSrcOver_Mode;

[reed1, 2015/07/31 15:33:42]

Why do we have default?

[hal.canary, 2015/07/31 15:41:59]

In case the user passes in garbage  

    sk_paint_set_xfermode_mode(p, (sk_xfermode_mode_t)199);

+    }
+}
+
+void sk_paint_set_xfermode_mode(sk_paint_t* paint, sk_xfermode_mode_t mode) {
+    AsPaint(paint)->setXfermodeMode(convert_skxfermodemode(mode));
+}