1 files changed, 70 insertions, 0 deletions
diff --git a/src/effects/gradients/SkLinearGradient.cpp b/src/effects/gradients/SkLinearGradient.cpp
index 4bb640de91..91c0e20955 100644
--- a/src/effects/gradients/SkLinearGradient.cpp
+++ b/src/effects/gradients/SkLinearGradient.cpp
@@ -86,6 +86,76 @@ SkShader::Context* SkLinearGradient::onCreateContext(const ContextRec& rec, void
         : CheckedCreateContext<  LinearGradientContext>(storage, *this, rec);
 }
 
+// For now, only a 2-stop raster pipeline specialization.
+//
+// Stages:
+//
+//   * matrix (map dst -> grad space)
+//   * clamp/repeat/mirror (tiling)
+//   * linear_gradient_2stops (lerp c0/c1)
+//   * optional premul
+//
+bool SkLinearGradient::onAppendStages(SkRasterPipeline* p, SkColorSpace* cs, SkArenaAlloc* alloc,
+                                      const SkMatrix& ctm, const SkPaint& paint) const {
+    if (fColorCount > 2) {
+        return false;
+    }
+
+    // Local matrix not supported currently.  Remove once we have a generic RP wrapper.
+    if (!getLocalMatrix().isIdentity()) {
+        return false;
+    }
+
+    SkASSERT(fColorCount == 2);
+    SkASSERT(fOrigPos == nullptr || (fOrigPos[0] == 0 && fOrigPos[1] == 1));
+
+    SkMatrix dstToPts;
+    if (!ctm.invert(&dstToPts)) {
+        return false;
+    }
+
+    const auto dstToUnit = SkMatrix::Concat(fPtsToUnit, dstToPts);
+
+    auto* m = alloc->makeArrayDefault<float>(9);
+    if (dstToUnit.asAffine(m)) {
+        // TODO: mapping y is not needed; split the matrix stages to save some math?
+        p->append(SkRasterPipeline::matrix_2x3, m);
+    } else {
+        dstToUnit.get9(m);
+        p->append(SkRasterPipeline::matrix_perspective, m);
+    }
+
+    // TODO: clamp/repeat/mirror const 1f stages?
+    auto* limit = alloc->make<float>(1.0f);
+
+    switch (fTileMode) {
+        case kClamp_TileMode:
+            *limit += 0.5f; // why is clamp_x offsetting its limit?
+            p->append(SkRasterPipeline::clamp_x, limit);
+            break;
+        case kMirror_TileMode: p->append(SkRasterPipeline::mirror_x, limit); break;
+        case kRepeat_TileMode: p->append(SkRasterPipeline::repeat_x, limit); break;
+    }
+
+    const bool premulGrad = fGradFlags & SkGradientShader::kInterpolateColorsInPremul_Flag;
+    const SkColor4f c0 = to_colorspace(fOrigColors4f[0], fColorSpace.get(), cs),
+                    c1 = to_colorspace(fOrigColors4f[1], fColorSpace.get(), cs);
+    const SkPM4f  pmc0 = premulGrad ? c0.premul() : SkPM4f::From4f(Sk4f::Load(&c0)),
+                  pmc1 = premulGrad ? c1.premul() : SkPM4f::From4f(Sk4f::Load(&c1));
+
+    auto* c0_and_dc = alloc->makeArrayDefault<SkPM4f>(2);
+    c0_and_dc[0] = pmc0;
+    c0_and_dc[1] = SkPM4f::From4f(pmc1.to4f() - pmc0.to4f());
+
+    p->append(SkRasterPipeline::linear_gradient_2stops, c0_and_dc);
+
+    if (!premulGrad && !this->colorsAreOpaque()) {
+        p->append(SkRasterPipeline::premul);
+    }
+
+    return true;
+}
+
 // This swizzles SkColor into the same component order as SkPMColor, but does not actually
 // "pre" multiply the color components.
 //