1 files changed, 119 insertions, 0 deletions
diff --git a/gfx/skia/skia/src/effects/SkTrimPathEffect.cpp b/gfx/skia/skia/src/effects/SkTrimPathEffect.cpp
new file mode 100644
index 0000000000..d0a8806d40
--- /dev/null
+++ b/gfx/skia/skia/src/effects/SkTrimPathEffect.cpp
@@ -0,0 +1,119 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "include/core/SkPathMeasure.h"
+#include "include/effects/SkTrimPathEffect.h"
+#include "src/core/SkReadBuffer.h"
+#include "src/core/SkWriteBuffer.h"
+#include "src/effects/SkTrimPE.h"
+
+namespace {
+
+class Segmentator : public SkNoncopyable {
+public:
+    Segmentator(const SkPath& src, SkPath* dst)
+        : fMeasure(src, false)
+        , fDst(dst) {}
+
+    void add(SkScalar start, SkScalar stop) {
+        SkASSERT(start < stop);
+
+        // TODO: we appear to skip zero-length contours.
+        do {
+            const auto nextOffset = fCurrentSegmentOffset + fMeasure.getLength();
+
+            if (start < nextOffset) {
+                fMeasure.getSegment(start - fCurrentSegmentOffset,
+                                    stop  - fCurrentSegmentOffset,
+                                    fDst, true);
+
+                if (stop < nextOffset)
+                    break;
+            }
+
+            fCurrentSegmentOffset = nextOffset;
+        } while (fMeasure.nextContour());
+    }
+
+private:
+    SkPathMeasure fMeasure;
+    SkPath*       fDst;
+
+    SkScalar fCurrentSegmentOffset = 0;
+
+    using INHERITED = SkNoncopyable;
+};
+
+} // namespace
+
+SkTrimPE::SkTrimPE(SkScalar startT, SkScalar stopT, SkTrimPathEffect::Mode mode)
+    : fStartT(startT), fStopT(stopT), fMode(mode) {}
+
+bool SkTrimPE::onFilterPath(SkPath* dst, const SkPath& src, SkStrokeRec* rec,
+                            const SkRect* cullRect) const {
+    if (fStartT >= fStopT) {
+        SkASSERT(fMode == SkTrimPathEffect::Mode::kNormal);
+        return true;
+    }
+
+    // First pass: compute the total len.
+    SkScalar len = 0;
+    SkPathMeasure meas(src, false);
+    do {
+        len += meas.getLength();
+    } while (meas.nextContour());
+
+    const auto arcStart = len * fStartT,
+               arcStop  = len * fStopT;
+
+    // Second pass: actually add segments.
+    Segmentator segmentator(src, dst);
+    if (fMode == SkTrimPathEffect::Mode::kNormal) {
+        if (arcStart < arcStop) segmentator.add(arcStart, arcStop);
+    } else {
+        if (0 <  arcStart) segmentator.add(0,  arcStart);
+        if (arcStop < len) segmentator.add(arcStop, len);
+    }
+
+    return true;
+}
+
+void SkTrimPE::flatten(SkWriteBuffer& buffer) const {
+    buffer.writeScalar(fStartT);
+    buffer.writeScalar(fStopT);
+    buffer.writeUInt(static_cast<uint32_t>(fMode));
+}
+
+sk_sp<SkFlattenable> SkTrimPE::CreateProc(SkReadBuffer& buffer) {
+    const auto start = buffer.readScalar(),
+               stop  = buffer.readScalar();
+    const auto mode  = buffer.readUInt();
+
+    return SkTrimPathEffect::Make(start, stop,
+        (mode & 1) ? SkTrimPathEffect::Mode::kInverted : SkTrimPathEffect::Mode::kNormal);
+}
+
+//////////////////////////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkPathEffect> SkTrimPathEffect::Make(SkScalar startT, SkScalar stopT, Mode mode) {
+    if (!SkScalarsAreFinite(startT, stopT)) {
+        return nullptr;
+    }
+
+    if (startT <= 0 && stopT >= 1 && mode == Mode::kNormal) {
+        return nullptr;
+    }
+
+    startT = SkTPin(startT, 0.f, 1.f);
+    stopT  = SkTPin(stopT,  0.f, 1.f);
+
+    if (startT >= stopT && mode == Mode::kInverted) {
+        return nullptr;
+    }
+
+    return sk_sp<SkPathEffect>(new SkTrimPE(startT, stopT, mode));
+}