gm/dashcircle.cpp

   1 /*
   2  * Copyright 2016 Google Inc.
   3  *
   4  * Use of this source code is governed by a BSD-style license that can be
   5  * found in the LICENSE file.
   6  */
   7
   8 #include "gm.h"
   9 #include "SkAnimTimer.h"
  10 #include "SkPath.h"
  11 #include "SkDashPathEffect.h"
  12
  13 int dash1[] = { 1, 1 };
  14 int dash2[] = { 1, 3 };
  15 int dash3[] = { 1, 1, 3, 3 };
  16 int dash4[] = { 1, 3, 2, 4 };
  17
  18 struct DashExample {
  19     int* pattern;
  20     int length;
  21 } dashExamples[] = {
  22     { dash1, SK_ARRAY_COUNT(dash1) },
  23     { dash2, SK_ARRAY_COUNT(dash2) },
  24     { dash3, SK_ARRAY_COUNT(dash3) },
  25     { dash4, SK_ARRAY_COUNT(dash4) }
  26 };
  27
  28
  29 class DashCircleGM : public skiagm::GM {
  30 public:
  31     DashCircleGM() : fRotation(0) { }
  32
  33 protected:
  34     SkString onShortName() override { return SkString("dashcircle"); }
  35
  36     SkISize onISize() override { return SkISize::Make(900, 1200); }
  37
  38     void onDraw(SkCanvas* canvas) override {
  39         SkPaint refPaint;
  40         refPaint.setAntiAlias(true);
  41         refPaint.setColor(0xFFbf3f7f);
  42         refPaint.setStyle(SkPaint::kStroke_Style);
  43         refPaint.setStrokeWidth(1);
  44         const SkScalar radius = 125;
  45         SkRect oval = SkRect::MakeLTRB(-radius - 20, -radius - 20, radius + 20, radius + 20);
  46         SkPath circle;
  47         circle.addCircle(0, 0, radius);
  48         SkScalar circumference = radius * SK_ScalarPI * 2;
  49         int wedges[] = { 6, 12, 36 };
  50         canvas->translate(radius+20, radius+20);
  51         for (int wedge : wedges) {
  52             SkScalar arcLength = 360.f / wedge;
  53             canvas->save();
  54             for (const DashExample& dashExample : dashExamples) {
  55                 SkPath refPath;
  56                 int dashUnits = 0;
  57                 for (int index = 0; index < dashExample.length; ++index) {
  58                     dashUnits += dashExample.pattern[index];
  59                 }
  60                 SkScalar unitLength = arcLength / dashUnits;
  61                 SkScalar angle = 0;
  62                 for (int index = 0; index < wedge; ++index) {
  63                     for (int i2 = 0; i2 < dashExample.length; i2 += 2) {
  64                         SkScalar span = dashExample.pattern[i2] * unitLength;
  65                         refPath.moveTo(0, 0);
  66                         refPath.arcTo(oval, angle, span, false);
  67                         refPath.close();
  68                         angle += span + (dashExample.pattern[i2 + 1]) * unitLength;
  69                     }
  70                 }
  71                 canvas->save();
  72                 canvas->rotate(fRotation);
  73                 canvas->drawPath(refPath, refPaint);
  74                 canvas->restore();
  75                 SkPaint p;
  76                 p.setAntiAlias(true);
  77                 p.setStyle(SkPaint::kStroke_Style);
  78                 p.setStrokeWidth(10);
  79                 SkScalar intervals[4];
  80                 int intervalCount = dashExample.length;
  81                 SkScalar dashLength = circumference / wedge / dashUnits;
  82                 for (int index = 0; index < dashExample.length; ++index) {
  83                     intervals[index] = dashExample.pattern[index] * dashLength;
  84                 }
  85                 p.setPathEffect(SkDashPathEffect::Make(intervals, intervalCount, 0));
  86                 canvas->save();
  87                 canvas->rotate(fRotation);
  88                 canvas->drawPath(circle, p);
  89                 canvas->restore();
  90                 canvas->translate(0, radius * 2 + 50);
  91             }
  92             canvas->restore();
  93             canvas->translate(radius * 2 + 50, 0);
  94         }
  95     }
  96
  97     bool onAnimate(const SkAnimTimer& timer) override {
  98         constexpr SkScalar kDesiredDurationSecs = 100.0f;
  99
 100         fRotation = timer.scaled(360.0f/kDesiredDurationSecs, 360.0f);
 101         return true;
 102     }
 103
 104 private:
 105     SkScalar fRotation;
 106
 107     typedef GM INHERITED;
 108 };
 109
 110 DEF_GM(return new DashCircleGM; )