add TrimPathEffect

Bug: skia:
Change-Id: I453fb81ded4435b33567e9c8a6f3abe9535d687f
Reviewed-on: https://skia-review.googlesource.com/112820
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>

7 files changed, 175 insertions, 1 deletions

diff --git a/gm/dashcubics.cpp b/gm/dashcubics.cpp
index e8d7f5bc8e..1d80d75b4a 100644
--- a/gm/dashcubics.cpp
+++ b/gm/dashcubics.cpp
@@ -58,3 +58,43 @@ DEF_SIMPLE_GM(dashcubics, canvas, 865, 750) {
             }
         }
 }
+
+#include "SkTrimPathEffect.h"
+class TrimGM : public skiagm::GM {
+public:
+    TrimGM() {}
+
+protected:
+    SkString onShortName() override { return SkString("trimpatheffect"); }
+
+    SkISize onISize() override { return SkISize::Make(1240, 390); }
+
+    void onDraw(SkCanvas* canvas) override {
+        SkPaint paint;
+        paint.setPathEffect(SkTrimPathEffect::Make(0.25 + fOffset, 0.75));
+        paint.setStyle(SkPaint::kStroke_Style);
+        paint.setAntiAlias(true);
+        paint.setStrokeWidth(10);
+
+        SkPath path;
+        path.moveTo(50, 300);
+        path.cubicTo(100, 50, 150, 550, 200, 300);
+
+        paint.setColor(0xFF888888);
+        canvas->drawPath(path, paint);
+        paint.setPathEffect(nullptr);
+        paint.setStrokeWidth(0);
+        paint.setColor(0xFF000000);
+        canvas->drawPath(path, paint);
+    }
+
+    bool onAnimate(const SkAnimTimer&) override {
+   //     fOffset += 1;
+        return true;
+    }
+private:
+    SkScalar fOffset = 0;
+    typedef skiagm::GM INHERITED;
+};
+DEF_GM(return new TrimGM;)
+
diff --git a/gn/effects.gni b/gn/effects.gni
index 5fb37e6bec..5b6a5fe21b 100644
--- a/gn/effects.gni
+++ b/gn/effects.gni
@@ -56,6 +56,7 @@ skia_effects_sources = [
   "$_src/effects/SkTableMaskFilter.cpp",
   "$_src/effects/SkTileImageFilter.cpp",
   "$_src/effects/SkToSRGBColorFilter.cpp",
+  "$_src/effects/SkTrimPathEffect.cpp",
   "$_src/effects/SkXfermodeImageFilter.cpp",
 
   "$_src/shaders/SkPerlinNoiseShader.cpp",
diff --git a/include/effects/SkTrimPathEffect.h b/include/effects/SkTrimPathEffect.h
new file mode 100644
index 0000000000..d40c9e2bbf
--- /dev/null
+++ b/include/effects/SkTrimPathEffect.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkTrimPathEffect_DEFINED
+#define SkTrimPathEffect_DEFINED
+
+#include "SkPathEffect.h"
+
+class SK_API SkTrimPathEffect {
+public:
+    /**
+     *  Take start and stop "t" values (values between 0...1), and return a path that is that
+     *  subset of the original path.
+     *
+     *  e.g.
+     *      Make(0.5, 1.0) --> return the 2nd half of the path
+     *      Make(0.33333, 0.66667) --> return the middle third of the path
+     *
+     *  The trim values apply to the entire path, so if it contains several contours, all of them
+     *  are including in the calculation.
+     *
+     *  startT and stopT must be 0..1 inclusive. If they are outside of that interval, they will
+     *  be pinned to the nearest legal value. If either is NaN, null will be returned.
+     *
+     *  Note: if startT < stopT, this will return one (logical) segment (even if it is spread
+     *        across multiple contours). If startT > stopT, then this will return 2 logical
+     *        segments: 0...stopT and startT...1
+     */
+    static sk_sp<SkPathEffect> Make(SkScalar startT, SkScalar stopT);
+};
+
+#endif
diff --git a/src/effects/SkDashImpl.h b/src/effects/SkDashImpl.h
index cf74529934..c4e81478c7 100644
--- a/src/effects/SkDashImpl.h
+++ b/src/effects/SkDashImpl.h
@@ -10,7 +10,7 @@
 
 #include "SkPathEffect.h"
 
-class SK_API SkDashImpl : public SkPathEffect {
+class SkDashImpl : public SkPathEffect {
 public:
     SkDashImpl(const SkScalar intervals[], int count, SkScalar phase);
 
diff --git a/src/effects/SkTrimPE.h b/src/effects/SkTrimPE.h
new file mode 100644
index 0000000000..2cd39c4793
--- /dev/null
+++ b/src/effects/SkTrimPE.h
@@ -0,0 +1,32 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkTrimImpl_DEFINED
+#define SkTrimImpl_DEFINED
+
+#include "SkPathEffect.h"
+
+class SkTrimPE : public SkPathEffect {
+public:
+    SkTrimPE(SkScalar startT, SkScalar stopT);
+
+    bool filterPath(SkPath* dst, const SkPath& src, SkStrokeRec*, const SkRect*) const override;
+
+    SK_TO_STRING_OVERRIDE()
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkTrimPE)
+
+protected:
+    void flatten(SkWriteBuffer&) const override;
+
+private:
+    const SkScalar fStartT;
+    const SkScalar fStopT;
+
+    typedef SkPathEffect INHERITED;
+};
+
+#endif
diff --git a/src/effects/SkTrimPathEffect.cpp b/src/effects/SkTrimPathEffect.cpp
new file mode 100644
index 0000000000..beaa36e17d
--- /dev/null
+++ b/src/effects/SkTrimPathEffect.cpp
@@ -0,0 +1,63 @@
+/*
+ * 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 "SkPathMeasure.h"
+#include "SkTrimPathEffect.h"
+#include "SkTrimPE.h"
+#include "SkReadBuffer.h"
+#include "SkWriteBuffer.h"
+
+SkTrimPE::SkTrimPE(SkScalar startT, SkScalar stopT) : fStartT(startT), fStopT(stopT) {
+    SkASSERT(startT >= 0 && startT <= 1);
+    SkASSERT(stopT >= 0 && stopT <= 1);
+    SkASSERT(startT != stopT);
+}
+
+bool SkTrimPE::filterPath(SkPath* dst, const SkPath& src, SkStrokeRec* rec,
+                            const SkRect* cullRect) const {
+    SkPathMeasure meas(src, false);
+    SkScalar length = meas.getLength();
+
+    if (fStartT < fStopT) {
+        meas.getSegment(fStartT * length, fStopT * length, dst, true);
+    } else {
+        meas.getSegment(0, fStopT * length, dst, true);
+        meas.getSegment(fStartT * length, length, dst, true);
+    }
+    return true;
+}
+
+void SkTrimPE::flatten(SkWriteBuffer& buffer) const {
+    buffer.writeScalar(fStartT);
+    buffer.writeScalar(fStopT);
+}
+
+sk_sp<SkFlattenable> SkTrimPE::CreateProc(SkReadBuffer& buffer) {
+    SkScalar start = buffer.readScalar();
+    SkScalar stop = buffer.readScalar();
+    return SkTrimPathEffect::Make(start, stop);
+}
+
+#ifndef SK_IGNORE_TO_STRING
+void SkTrimPE::toString(SkString* str) const {
+    str->appendf("SkTrimPathEffect: (%g %g)", fStartT, fStopT);
+}
+#endif
+
+//////////////////////////////////////////////////////////////////////////////////////////////////
+
+sk_sp<SkPathEffect> SkTrimPathEffect::Make(SkScalar startT, SkScalar stopT) {
+    if (!SkScalarsAreFinite(startT, stopT)) {
+        return nullptr;
+    }
+    startT = SkTPin(startT, 0.f, 1.f);
+    stopT  = SkTPin(stopT,  0.f, 1.f);
+    if (startT == stopT) {
+        return nullptr;
+    }
+    return sk_sp<SkPathEffect>(new SkTrimPE(startT, stopT));
+}
diff --git a/src/ports/SkGlobalInitialization_default.cpp b/src/ports/SkGlobalInitialization_default.cpp
index bf6ea14323..ebfedb276d 100644
--- a/src/ports/SkGlobalInitialization_default.cpp
+++ b/src/ports/SkGlobalInitialization_default.cpp
@@ -40,6 +40,7 @@
 #include "SkTableColorFilter.h"
 #include "SkTileImageFilter.h"
 #include "SkToSRGBColorFilter.h"
+#include "../../src/effects/SkTrimPE.h"
 #include "SkXfermodeImageFilter.h"
 
 // Security note:
@@ -90,6 +91,7 @@ void SkFlattenable::PrivateInitializer::InitEffects() {
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkPath1DPathEffect)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkLine2DPathEffect)
     SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkPath2DPathEffect)
+    SK_DEFINE_FLATTENABLE_REGISTRAR_ENTRY(SkTrimPE)
 
     // ImageFilter
     SkImageFilter::InitializeFlattenables();