Tiling support for SkSweepGradient

Expand the sweep gradient definition to include a color stop angular range ([0, 360] by default).

Color stop positions in [0,1] are mapped to this range, and drawing outside is controlled by a
tile mode param.

This is closer to the CSS gradients spec and allows us to use fewer color stops in Blink conic
gradients.

Impl-wise, the remapping is effected after t calculation, and before tiling.

Change-Id: I5d71be01d134404d6eb9d7e2a904ec636b39f855
Reviewed-on: https://skia-review.googlesource.com/27704
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>

1 files changed, 45 insertions, 20 deletions

diff --git a/include/effects/SkGradientShader.h b/include/effects/SkGradientShader.h
index 393749be65..a4408ad9c3 100644
--- a/include/effects/SkGradientShader.h
+++ b/include/effects/SkGradientShader.h
@@ -158,44 +158,69 @@ public:
 
     /** Returns a shader that generates a sweep gradient given a center.
         <p />
-        @param  cx      The X coordinate of the center of the sweep
-        @param  cx      The Y coordinate of the center of the sweep
-        @param  colors  The array[count] of colors, to be distributed around the center.
-        @param  pos     May be NULL. The array[count] of SkScalars, or NULL, of the relative position of
-                        each corresponding color in the colors array. If this is NULL,
-                        the the colors are distributed evenly between the center and edge of the circle.
-                        If this is not null, the values must begin with 0, end with 1.0, and
-                        intermediate values must be strictly increasing.
-        @param  count   Must be >= 2. The number of colors (and pos if not NULL) entries
+        @param  cx         The X coordinate of the center of the sweep
+        @param  cx         The Y coordinate of the center of the sweep
+        @param  colors     The array[count] of colors, to be distributed around the center, within
+                           the gradient angle range.
+        @param  pos        May be NULL. The array[count] of SkScalars, or NULL, of the relative
+                           position of each corresponding color in the colors array. If this is
+                           NULL, then the colors are distributed evenly within the angular range.
+                           If this is not null, the values must begin with 0, end with 1.0, and
+                           intermediate values must be strictly increasing.
+        @param  count      Must be >= 2. The number of colors (and pos if not NULL) entries
+        @param  mode       Tiling mode: controls drawing outside of the gradient angular range.
+        @param  startAngle Start of the angular range, corresponding to pos == 0.
+        @param  endAngle   End of the angular range, corresponding to pos == 1.
     */
     static sk_sp<SkShader> MakeSweep(SkScalar cx, SkScalar cy,
                                      const SkColor colors[], const SkScalar pos[], int count,
+                                     SkShader::TileMode mode,
+                                     SkScalar startAngle, SkScalar endAngle,
                                      uint32_t flags, const SkMatrix* localMatrix);
     static sk_sp<SkShader> MakeSweep(SkScalar cx, SkScalar cy,
+                                     const SkColor colors[], const SkScalar pos[], int count,
+                                     uint32_t flags, const SkMatrix* localMatrix) {
+        return MakeSweep(cx, cy, colors, pos, count, SkShader::kClamp_TileMode, 0, 360, flags,
+                         localMatrix);
+    }
+    static sk_sp<SkShader> MakeSweep(SkScalar cx, SkScalar cy,
                                      const SkColor colors[], const SkScalar pos[], int count) {
-        return MakeSweep(cx, cy, colors, pos, count, 0, NULL);
+        return MakeSweep(cx, cy, colors, pos, count, 0, nullptr);
     }
 
     /** Returns a shader that generates a sweep gradient given a center.
         <p />
-        @param  cx      The X coordinate of the center of the sweep
-        @param  cx      The Y coordinate of the center of the sweep
-        @param  colors  The array[count] of colors, to be distributed around the center.
-        @param  pos     May be NULL. The array[count] of SkScalars, or NULL, of the relative position of
-                        each corresponding color in the colors array. If this is NULL,
-                        the the colors are distributed evenly between the center and edge of the circle.
-                        If this is not null, the values must begin with 0, end with 1.0, and
-                        intermediate values must be strictly increasing.
-        @param  count   Must be >= 2. The number of colors (and pos if not NULL) entries
+        @param  cx         The X coordinate of the center of the sweep
+        @param  cx         The Y coordinate of the center of the sweep
+        @param  colors     The array[count] of colors, to be distributed around the center, within
+                           the gradient angle range.
+        @param  pos        May be NULL. The array[count] of SkScalars, or NULL, of the relative
+                           position of each corresponding color in the colors array. If this is
+                           NULL, then the colors are distributed evenly within the angular range.
+                           If this is not null, the values must begin with 0, end with 1.0, and
+                           intermediate values must be strictly increasing.
+        @param  count      Must be >= 2. The number of colors (and pos if not NULL) entries
+        @param  mode       Tiling mode: controls drawing outside of the gradient angular range.
+        @param  startAngle Start of the angular range, corresponding to pos == 0.
+        @param  endAngle   End of the angular range, corresponding to pos == 1.
     */
     static sk_sp<SkShader> MakeSweep(SkScalar cx, SkScalar cy,
                                      const SkColor4f colors[], sk_sp<SkColorSpace> colorSpace,
                                      const SkScalar pos[], int count,
+                                     SkShader::TileMode mode,
+                                     SkScalar startAngle, SkScalar endAngle,
                                      uint32_t flags, const SkMatrix* localMatrix);
     static sk_sp<SkShader> MakeSweep(SkScalar cx, SkScalar cy,
                                      const SkColor4f colors[], sk_sp<SkColorSpace> colorSpace,
+                                     const SkScalar pos[], int count,
+                                     uint32_t flags, const SkMatrix* localMatrix) {
+        return MakeSweep(cx, cy, colors, std::move(colorSpace), pos, count,
+                         SkShader::kClamp_TileMode, 0, 360, flags, localMatrix);
+    }
+    static sk_sp<SkShader> MakeSweep(SkScalar cx, SkScalar cy,
+                                     const SkColor4f colors[], sk_sp<SkColorSpace> colorSpace,
                                      const SkScalar pos[], int count) {
-        return MakeSweep(cx, cy, colors, std::move(colorSpace), pos, count, 0, NULL);
+        return MakeSweep(cx, cy, colors, std::move(colorSpace), pos, count, 0, nullptr);
     }
 
     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()