xref: /aosp_15_r20/external/skia/gm/dashing.cpp (revision c8dee2aa9b3f27cf6c858bd81872bdeb2c07ed17)
1 /*
2  * Copyright 2012 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/gm.h"
9 #include "include/core/SkCanvas.h"
10 #include "include/core/SkColor.h"
11 #include "include/core/SkFont.h"
12 #include "include/core/SkMatrix.h"
13 #include "include/core/SkPaint.h"
14 #include "include/core/SkPathBuilder.h"
15 #include "include/core/SkPathEffect.h"
16 #include "include/core/SkPoint.h"
17 #include "include/core/SkRect.h"
18 #include "include/core/SkScalar.h"
19 #include "include/core/SkSize.h"
20 #include "include/core/SkString.h"
21 #include "include/core/SkTypeface.h"
22 #include "include/core/SkTypes.h"
23 #include "include/effects/SkDashPathEffect.h"
24 #include "tools/ToolUtils.h"
25 #include "tools/fonts/FontToolUtils.h"
26 
27 #include <math.h>
28 #include <initializer_list>
29 
drawline(SkCanvas * canvas,int on,int off,const SkPaint & paint,SkScalar finalX=SkIntToScalar (600),SkScalar finalY=SkIntToScalar (0),SkScalar phase=SkIntToScalar (0),SkScalar startX=SkIntToScalar (0),SkScalar startY=SkIntToScalar (0))30 static void drawline(SkCanvas* canvas, int on, int off, const SkPaint& paint,
31                      SkScalar finalX = SkIntToScalar(600), SkScalar finalY = SkIntToScalar(0),
32                      SkScalar phase = SkIntToScalar(0),
33                      SkScalar startX = SkIntToScalar(0), SkScalar startY = SkIntToScalar(0)) {
34     SkPaint p(paint);
35 
36     const SkScalar intervals[] = {
37         SkIntToScalar(on),
38         SkIntToScalar(off),
39     };
40 
41     p.setPathEffect(SkDashPathEffect::Make(intervals, 2, phase));
42     canvas->drawLine(startX, startY, finalX, finalY, p);
43 }
44 
45 // earlier bug stopped us from drawing very long single-segment dashes, because
46 // SkPathMeasure was skipping very small delta-T values (nearlyzero). This is
47 // now fixes, so this giant dash should appear.
show_giant_dash(SkCanvas * canvas)48 static void show_giant_dash(SkCanvas* canvas) {
49     SkPaint paint;
50 
51     drawline(canvas, 1, 1, paint, SkIntToScalar(20 * 1000));
52 }
53 
show_zero_len_dash(SkCanvas * canvas)54 static void show_zero_len_dash(SkCanvas* canvas) {
55     SkPaint paint;
56 
57     drawline(canvas, 2, 2, paint, SkIntToScalar(0));
58     paint.setStroke(true);
59     paint.setStrokeWidth(SkIntToScalar(2));
60     canvas->translate(0, SkIntToScalar(20));
61     drawline(canvas, 4, 4, paint, SkIntToScalar(0));
62 }
63 
64 class DashingGM : public skiagm::GM {
getName() const65     SkString getName() const override { return SkString("dashing"); }
66 
getISize()67     SkISize getISize() override { return {640, 340}; }
68 
onDraw(SkCanvas * canvas)69     void onDraw(SkCanvas* canvas) override {
70         struct Intervals {
71             int fOnInterval;
72             int fOffInterval;
73         };
74 
75         SkPaint paint;
76         paint.setStroke(true);
77 
78         canvas->translate(SkIntToScalar(20), SkIntToScalar(20));
79         canvas->translate(0, SK_ScalarHalf);
80         for (int width = 0; width <= 2; ++width) {
81             for (const Intervals& data : {Intervals{1, 1},
82                                           Intervals{4, 1}}) {
83                 for (bool aa : {false, true}) {
84                     int w = width * width * width;
85                     paint.setAntiAlias(aa);
86                     paint.setStrokeWidth(SkIntToScalar(w));
87 
88                     int scale = w ? w : 1;
89 
90                     drawline(canvas, data.fOnInterval * scale, data.fOffInterval * scale,
91                              paint);
92                     canvas->translate(0, SkIntToScalar(20));
93                 }
94             }
95         }
96 
97         show_giant_dash(canvas);
98         canvas->translate(0, SkIntToScalar(20));
99         show_zero_len_dash(canvas);
100         canvas->translate(0, SkIntToScalar(20));
101         // Draw 0 on, 0 off dashed line
102         paint.setStrokeWidth(SkIntToScalar(8));
103         drawline(canvas, 0, 0, paint);
104     }
105 };
106 
107 ///////////////////////////////////////////////////////////////////////////////
108 
make_unit_star(int n)109 static SkPath make_unit_star(int n) {
110     SkScalar rad = -SK_ScalarPI / 2;
111     const SkScalar drad = (n >> 1) * SK_ScalarPI * 2 / n;
112 
113     SkPathBuilder b;
114     b.moveTo(0, -SK_Scalar1);
115     for (int i = 1; i < n; i++) {
116         rad += drad;
117         b.lineTo(SkScalarCos(rad), SkScalarSin(rad));
118     }
119     return b.close().detach();
120 }
121 
make_path_line(const SkRect & bounds)122 static SkPath make_path_line(const SkRect& bounds) {
123     return SkPathBuilder().moveTo(bounds.left(), bounds.top())
124                           .lineTo(bounds.right(), bounds.bottom())
125                           .detach();
126 }
127 
make_path_rect(const SkRect & bounds)128 static SkPath make_path_rect(const SkRect& bounds) {
129     return SkPath::Rect(bounds);
130 }
131 
make_path_oval(const SkRect & bounds)132 static SkPath make_path_oval(const SkRect& bounds) {
133     return SkPath::Oval(bounds);
134 }
135 
make_path_star(const SkRect & bounds)136 static SkPath make_path_star(const SkRect& bounds) {
137     SkPath path = make_unit_star(5);
138     SkMatrix matrix = SkMatrix::RectToRect(path.getBounds(), bounds, SkMatrix::kCenter_ScaleToFit);
139     return path.makeTransform(matrix);
140 }
141 
142 class Dashing2GM : public skiagm::GM {
getName() const143     SkString getName() const override { return SkString("dashing2"); }
144 
getISize()145     SkISize getISize() override { return {640, 480}; }
146 
onDraw(SkCanvas * canvas)147     void onDraw(SkCanvas* canvas) override {
148         constexpr int gIntervals[] = {
149             3,  // 3 dashes: each count [0] followed by intervals [1..count]
150             2,  10, 10,
151             4,  20, 5, 5, 5,
152             2,  2, 2
153         };
154 
155         SkPath (*gProc[])(const SkRect&) = {
156             make_path_line, make_path_rect, make_path_oval, make_path_star,
157         };
158 
159         SkPaint paint;
160         paint.setAntiAlias(true);
161         paint.setStroke(true);
162         paint.setStrokeWidth(SkIntToScalar(6));
163 
164         SkRect bounds = SkRect::MakeWH(SkIntToScalar(120), SkIntToScalar(120));
165         bounds.offset(SkIntToScalar(20), SkIntToScalar(20));
166         SkScalar dx = bounds.width() * 4 / 3;
167         SkScalar dy = bounds.height() * 4 / 3;
168 
169         const int* intervals = &gIntervals[1];
170         for (int y = 0; y < gIntervals[0]; ++y) {
171             SkScalar vals[std::size(gIntervals)];  // more than enough
172             int count = *intervals++;
173             for (int i = 0; i < count; ++i) {
174                 vals[i] = SkIntToScalar(*intervals++);
175             }
176             SkScalar phase = vals[0] / 2;
177             paint.setPathEffect(SkDashPathEffect::Make(vals, count, phase));
178 
179             for (size_t x = 0; x < std::size(gProc); ++x) {
180                 SkPath path;
181                 SkRect r = bounds;
182                 r.offset(x * dx, y * dy);
183                 canvas->drawPath(gProc[x](r), paint);
184             }
185         }
186     }
187 };
188 
189 //////////////////////////////////////////////////////////////////////////////
190 
191 // Test out the on/off line dashing Chrome if fond of
192 class Dashing3GM : public skiagm::GM {
getName() const193     SkString getName() const override { return SkString("dashing3"); }
194 
getISize()195     SkISize getISize() override { return {640, 480}; }
196 
197     // Draw a 100x100 block of dashed lines. The horizontal ones are BW
198     // while the vertical ones are AA.
drawDashedLines(SkCanvas * canvas,SkScalar lineLength,SkScalar phase,SkScalar dashLength,int strokeWidth,bool circles)199     void drawDashedLines(SkCanvas* canvas,
200                          SkScalar lineLength,
201                          SkScalar phase,
202                          SkScalar dashLength,
203                          int strokeWidth,
204                          bool circles) {
205         SkPaint p;
206         p.setColor(SK_ColorBLACK);
207         p.setStroke(true);
208         p.setStrokeWidth(SkIntToScalar(strokeWidth));
209 
210         if (circles) {
211             p.setStrokeCap(SkPaint::kRound_Cap);
212         }
213 
214         SkScalar intervals[2] = { dashLength, dashLength };
215 
216         p.setPathEffect(SkDashPathEffect::Make(intervals, 2, phase));
217 
218         SkPoint pts[2];
219 
220         for (int y = 0; y < 100; y += 10*strokeWidth) {
221             pts[0].set(0, SkIntToScalar(y));
222             pts[1].set(lineLength, SkIntToScalar(y));
223 
224             canvas->drawPoints(SkCanvas::kLines_PointMode, 2, pts, p);
225         }
226 
227         p.setAntiAlias(true);
228 
229         for (int x = 0; x < 100; x += 14*strokeWidth) {
230             pts[0].set(SkIntToScalar(x), 0);
231             pts[1].set(SkIntToScalar(x), lineLength);
232 
233             canvas->drawPoints(SkCanvas::kLines_PointMode, 2, pts, p);
234         }
235     }
236 
onDraw(SkCanvas * canvas)237     void onDraw(SkCanvas* canvas) override {
238         // 1on/1off 1x1 squares with phase of 0 - points fastpath
239         canvas->save();
240             canvas->translate(2, 0);
241             this->drawDashedLines(canvas, 100, 0, SK_Scalar1, 1, false);
242         canvas->restore();
243 
244         // 1on/1off 1x1 squares with phase of .5 - rects fastpath (due to partial squares)
245         canvas->save();
246             canvas->translate(112, 0);
247             this->drawDashedLines(canvas, 100, SK_ScalarHalf, SK_Scalar1, 1, false);
248         canvas->restore();
249 
250         // 1on/1off 1x1 squares with phase of 1 - points fastpath
251         canvas->save();
252             canvas->translate(222, 0);
253             this->drawDashedLines(canvas, 100, SK_Scalar1, SK_Scalar1, 1, false);
254         canvas->restore();
255 
256         // 1on/1off 1x1 squares with phase of 1 and non-integer length - rects fastpath
257         canvas->save();
258             canvas->translate(332, 0);
259             this->drawDashedLines(canvas, 99.5f, SK_ScalarHalf, SK_Scalar1, 1, false);
260         canvas->restore();
261 
262         // 255on/255off 1x1 squares with phase of 0 - rects fast path
263         canvas->save();
264             canvas->translate(446, 0);
265             this->drawDashedLines(canvas, 100, 0, SkIntToScalar(255), 1, false);
266         canvas->restore();
267 
268         // 1on/1off 3x3 squares with phase of 0 - points fast path
269         canvas->save();
270             canvas->translate(2, 110);
271             this->drawDashedLines(canvas, 100, 0, SkIntToScalar(3), 3, false);
272         canvas->restore();
273 
274         // 1on/1off 3x3 squares with phase of 1.5 - rects fast path
275         canvas->save();
276             canvas->translate(112, 110);
277             this->drawDashedLines(canvas, 100, 1.5f, SkIntToScalar(3), 3, false);
278         canvas->restore();
279 
280         // 1on/1off 1x1 circles with phase of 1 - no fast path yet
281         canvas->save();
282             canvas->translate(2, 220);
283             this->drawDashedLines(canvas, 100, SK_Scalar1, SK_Scalar1, 1, true);
284         canvas->restore();
285 
286         // 1on/1off 3x3 circles with phase of 1 - no fast path yet
287         canvas->save();
288             canvas->translate(112, 220);
289             this->drawDashedLines(canvas, 100, 0, SkIntToScalar(3), 3, true);
290         canvas->restore();
291 
292         // 1on/1off 1x1 squares with rotation - should break fast path
293         canvas->save();
294             canvas->translate(332+SK_ScalarRoot2Over2*100, 110+SK_ScalarRoot2Over2*100);
295             canvas->rotate(45);
296             canvas->translate(-50, -50);
297 
298             this->drawDashedLines(canvas, 100, SK_Scalar1, SK_Scalar1, 1, false);
299         canvas->restore();
300 
301         // 3on/3off 3x1 rects - should use rect fast path regardless of phase
302         for (int phase = 0; phase <= 3; ++phase) {
303             canvas->save();
304                 canvas->translate(SkIntToScalar(phase*110+2),
305                                   SkIntToScalar(330));
306                 this->drawDashedLines(canvas, 100, SkIntToScalar(phase), SkIntToScalar(3), 1, false);
307             canvas->restore();
308         }
309     }
310 
311 };
312 
313 //////////////////////////////////////////////////////////////////////////////
314 
315 class Dashing4GM : public skiagm::GM {
getName() const316     SkString getName() const override { return SkString("dashing4"); }
317 
getISize()318     SkISize getISize() override { return {640, 1100}; }
319 
onDraw(SkCanvas * canvas)320     void onDraw(SkCanvas* canvas) override {
321         struct Intervals {
322             int fOnInterval;
323             int fOffInterval;
324         };
325 
326         SkPaint paint;
327         paint.setStroke(true);
328 
329         canvas->translate(SkIntToScalar(20), SkIntToScalar(20));
330         canvas->translate(SK_ScalarHalf, SK_ScalarHalf);
331 
332         for (int width = 0; width <= 2; ++width) {
333             for (const Intervals& data : {Intervals{1, 1},
334                                           Intervals{4, 2},
335                                           Intervals{0, 4}}) { // test for zero length on interval.
336                                                               // zero length intervals should draw
337                                                               // a line of squares or circles
338                 for (bool aa : {false, true}) {
339                     for (auto cap : {SkPaint::kRound_Cap, SkPaint::kSquare_Cap}) {
340                         int w = width * width * width;
341                         paint.setAntiAlias(aa);
342                         paint.setStrokeWidth(SkIntToScalar(w));
343                         paint.setStrokeCap(cap);
344 
345                         int scale = w ? w : 1;
346 
347                         drawline(canvas, data.fOnInterval * scale, data.fOffInterval * scale,
348                                  paint);
349                         canvas->translate(0, SkIntToScalar(20));
350                     }
351                 }
352             }
353         }
354 
355         for (int aa = 0; aa <= 1; ++aa) {
356             paint.setAntiAlias(SkToBool(aa));
357             paint.setStrokeWidth(8.f);
358             paint.setStrokeCap(SkPaint::kSquare_Cap);
359             // Single dash element that is cut off at start and end
360             drawline(canvas, 32, 16, paint, 20.f, 0, 5.f);
361             canvas->translate(0, SkIntToScalar(20));
362 
363             // Two dash elements where each one is cut off at beginning and end respectively
364             drawline(canvas, 32, 16, paint, 56.f, 0, 5.f);
365             canvas->translate(0, SkIntToScalar(20));
366 
367             // Many dash elements where first and last are cut off at beginning and end respectively
368             drawline(canvas, 32, 16, paint, 584.f, 0, 5.f);
369             canvas->translate(0, SkIntToScalar(20));
370 
371             // Diagonal dash line where src pnts are not axis aligned (as apposed to being diagonal from
372             // a canvas rotation)
373             drawline(canvas, 32, 16, paint, 600.f, 30.f);
374             canvas->translate(0, SkIntToScalar(20));
375 
376             // Case where only the off interval exists on the line. Thus nothing should be drawn
377             drawline(canvas, 32, 16, paint, 8.f, 0.f, 40.f);
378             canvas->translate(0, SkIntToScalar(20));
379         }
380 
381         // Test overlapping circles.
382         canvas->translate(SkIntToScalar(5), SkIntToScalar(20));
383         paint.setAntiAlias(true);
384         paint.setStrokeCap(SkPaint::kRound_Cap);
385         paint.setColor(0x44000000);
386         paint.setStrokeWidth(40);
387         drawline(canvas, 0, 30, paint);
388 
389         canvas->translate(0, SkIntToScalar(50));
390         paint.setStrokeCap(SkPaint::kSquare_Cap);
391         drawline(canvas, 0, 30, paint);
392 
393         // Test we draw the cap when the line length is zero.
394         canvas->translate(0, SkIntToScalar(50));
395         paint.setStrokeCap(SkPaint::kRound_Cap);
396         paint.setColor(0xFF000000);
397         paint.setStrokeWidth(11);
398         drawline(canvas, 0, 30, paint, 0);
399 
400         canvas->translate(SkIntToScalar(100), 0);
401         drawline(canvas, 1, 30, paint, 0);
402     }
403 };
404 
405 //////////////////////////////////////////////////////////////////////////////
406 
407 class Dashing5GM : public skiagm::GM {
408 public:
Dashing5GM(bool doAA)409     Dashing5GM(bool doAA) : fDoAA(doAA) {}
410 
411 private:
runAsBench() const412     bool runAsBench() const override { return true; }
413 
getName() const414     SkString getName() const override { return SkString(fDoAA ? "dashing5_aa" : "dashing5_bw"); }
415 
getISize()416     SkISize getISize() override { return {400, 200}; }
417 
onDraw(SkCanvas * canvas)418     void onDraw(SkCanvas* canvas) override {
419         constexpr int kOn = 4;
420         constexpr int kOff = 4;
421         constexpr int kIntervalLength = kOn + kOff;
422 
423         constexpr SkColor gColors[kIntervalLength] = {
424             SK_ColorRED,
425             SK_ColorGREEN,
426             SK_ColorBLUE,
427             SK_ColorCYAN,
428             SK_ColorMAGENTA,
429             SK_ColorYELLOW,
430             SK_ColorGRAY,
431             SK_ColorDKGRAY
432         };
433 
434         SkPaint paint;
435         paint.setStroke(true);
436 
437         paint.setAntiAlias(fDoAA);
438 
439         SkMatrix rot;
440         rot.setRotate(90);
441         SkASSERT(rot.rectStaysRect());
442 
443         canvas->concat(rot);
444 
445         int sign;       // used to toggle the direction of the lines
446         int phase = 0;
447 
448         for (int x = 0; x < 200; x += 10) {
449             paint.setStrokeWidth(SkIntToScalar(phase+1));
450             paint.setColor(gColors[phase]);
451             sign = (x % 20) ? 1 : -1;
452             drawline(canvas, kOn, kOff, paint,
453                      SkIntToScalar(x), -sign * SkIntToScalar(10003),
454                      SkIntToScalar(phase),
455                      SkIntToScalar(x),  sign * SkIntToScalar(10003));
456             phase = (phase + 1) % kIntervalLength;
457         }
458 
459         for (int y = -400; y < 0; y += 10) {
460             paint.setStrokeWidth(SkIntToScalar(phase+1));
461             paint.setColor(gColors[phase]);
462             sign = (y % 20) ? 1 : -1;
463             drawline(canvas, kOn, kOff, paint,
464                      -sign * SkIntToScalar(10003), SkIntToScalar(y),
465                      SkIntToScalar(phase),
466                       sign * SkIntToScalar(10003), SkIntToScalar(y));
467             phase = (phase + 1) % kIntervalLength;
468         }
469     }
470 
471 private:
472     bool fDoAA;
473 };
474 
475 DEF_SIMPLE_GM(longpathdash, canvas, 612, 612) {
476     SkPath lines;
477     for (int x = 32; x < 256; x += 16) {
478         for (SkScalar a = 0; a < 3.141592f * 2; a += 0.03141592f) {
479             SkPoint pts[2] = {
480                 { 256 + (float) sin(a) * x,
481                   256 + (float) cos(a) * x },
482                 { 256 + (float) sin(a + 3.141592 / 3) * (x + 64),
483                   256 + (float) cos(a + 3.141592 / 3) * (x + 64) }
484             };
485             lines.moveTo(pts[0]);
486             for (SkScalar i = 0; i < 1; i += 0.05f) {
487                 lines.lineTo(pts[0].fX * (1 - i) + pts[1].fX * i,
488                              pts[0].fY * (1 - i) + pts[1].fY * i);
489             }
490         }
491     }
492     SkPaint p;
493     p.setAntiAlias(true);
494     p.setStroke(true);
495     p.setStrokeWidth(1);
496     const SkScalar intervals[] = { 1, 1 };
497     p.setPathEffect(SkDashPathEffect::Make(intervals, std::size(intervals), 0));
498 
499     canvas->translate(50, 50);
500     canvas->drawPath(lines, p);
501 }
502 
503 DEF_SIMPLE_GM(longlinedash, canvas, 512, 512) {
504     SkPaint p;
505     p.setAntiAlias(true);
506     p.setStroke(true);
507     p.setStrokeWidth(80);
508 
509     const SkScalar intervals[] = { 2, 2 };
510     p.setPathEffect(SkDashPathEffect::Make(intervals, std::size(intervals), 0));
511     canvas->drawRect(SkRect::MakeXYWH(-10000, 100, 20000, 20), p);
512 }
513 
514 DEF_SIMPLE_GM(dashbigrects, canvas, 256, 256) {
515     SkRandom rand;
516 
517     constexpr int kHalfStrokeWidth = 8;
518     constexpr int kOnOffInterval = 2*kHalfStrokeWidth;
519 
520     canvas->clear(SkColors::kBlack);
521 
522     SkPaint p;
523     p.setAntiAlias(true);
524     p.setStroke(true);
525     p.setStrokeWidth(2*kHalfStrokeWidth);
526     p.setStrokeCap(SkPaint::kButt_Cap);
527 
528     constexpr SkScalar intervals[] = { kOnOffInterval, kOnOffInterval };
529     p.setPathEffect(SkDashPathEffect::Make(intervals, std::size(intervals), 0));
530 
531     constexpr float gWidthHeights[] = {
532         1000000000.0f * kOnOffInterval + kOnOffInterval/2.0f,
533         1000000.0f * kOnOffInterval + kOnOffInterval/2.0f,
534         1000.0f * kOnOffInterval + kOnOffInterval/2.0f,
535         100.0f * kOnOffInterval + kOnOffInterval/2.0f,
536         10.0f * kOnOffInterval + kOnOffInterval/2.0f,
537         9.0f * kOnOffInterval + kOnOffInterval/2.0f,
538         8.0f * kOnOffInterval + kOnOffInterval/2.0f,
539         7.0f * kOnOffInterval + kOnOffInterval/2.0f,
540         6.0f * kOnOffInterval + kOnOffInterval/2.0f,
541         5.0f * kOnOffInterval + kOnOffInterval/2.0f,
542         4.0f * kOnOffInterval + kOnOffInterval/2.0f,
543     };
544 
545     for (size_t i = 0; i < std::size(gWidthHeights); ++i) {
546         p.setColor(ToolUtils::color_to_565(rand.nextU() | (0xFF << 24)));
547 
548         int offset = 2 * i * kHalfStrokeWidth + kHalfStrokeWidth;
549         canvas->drawRect(SkRect::MakeXYWH(offset, offset, gWidthHeights[i], gWidthHeights[i]), p);
550     }
551 }
552 
553 DEF_SIMPLE_GM(longwavyline, canvas, 512, 512) {
554     SkPaint p;
555     p.setAntiAlias(true);
556     p.setStroke(true);
557     p.setStrokeWidth(2);
558 
559     SkPath wavy;
560     wavy.moveTo(-10000, 100);
561     for (SkScalar i = -10000; i < 10000; i += 20) {
562         wavy.quadTo(i + 5, 95, i + 10, 100);
563         wavy.quadTo(i + 15, 105, i + 20, 100);
564     }
565     canvas->drawPath(wavy, p);
566 }
567 
568 DEF_SIMPLE_GM(dashtextcaps, canvas, 512, 512) {
569     SkPaint p;
570     p.setAntiAlias(true);
571     p.setStroke(true);
572     p.setStrokeWidth(10);
573     p.setStrokeCap(SkPaint::kRound_Cap);
574     p.setStrokeJoin(SkPaint::kRound_Join);
575     p.setARGB(0xff, 0xbb, 0x00, 0x00);
576 
577     SkFont font(ToolUtils::DefaultPortableTypeface(), 100);
578 
579     const SkScalar intervals[] = { 12, 12 };
580     p.setPathEffect(SkDashPathEffect::Make(intervals, std::size(intervals), 0));
581     canvas->drawString("Sausages", 10, 90, font, p);
582     canvas->drawLine(8, 120, 456, 120, p);
583 }
584 
585 DEF_SIMPLE_GM(dash_line_zero_off_interval, canvas, 160, 330) {
586     static constexpr SkScalar kIntervals[] = {5.f, 0.f, 2.f, 0.f};
587     SkPaint dashPaint;
588     dashPaint.setPathEffect(SkDashPathEffect::Make(kIntervals, std::size(kIntervals), 0.f));
589     SkASSERT(dashPaint.getPathEffect());
590     dashPaint.setStroke(true);
591     dashPaint.setStrokeWidth(20.f);
592     static constexpr struct {
593         SkPoint fA, fB;
594     } kLines[] = {{{0.5f, 0.5f}, {30.5f, 0.5f}},    // horizontal
595                   {{0.5f, 0.5f}, {0.5f, 30.5f}},    // vertical
596                   {{0.5f, 0.5f}, {0.5f, 0.5f}},     // point
597                   {{0.5f, 0.5f}, {25.5f, 25.5f}}};  // diagonal
598     SkScalar pad = 5.f + dashPaint.getStrokeWidth();
599     canvas->translate(pad / 2.f, pad / 2.f);
600     canvas->save();
601     SkScalar h = 0.f;
602     for (const auto& line : kLines) {
603         h = std::max(h, SkScalarAbs(line.fA.fY - line.fB.fY));
604     }
605     for (const auto& line : kLines) {
606         SkScalar w = SkScalarAbs(line.fA.fX - line.fB.fX);
607         for (auto cap : {SkPaint::kButt_Cap, SkPaint::kSquare_Cap, SkPaint::kRound_Cap}) {
608             dashPaint.setStrokeCap(cap);
609             for (auto aa : {false, true}) {
610                 dashPaint.setAntiAlias(aa);
611                 canvas->drawLine(line.fA, line.fB, dashPaint);
612                 canvas->translate(0.f, pad + h);
613             }
614         }
615         canvas->restore();
616         canvas->translate(pad + w, 0.f);
617         canvas->save();
618     }
619 }
620 
621 DEF_SIMPLE_GM(thin_aa_dash_lines, canvas, 330, 110) {
622     SkPaint paint;
623     static constexpr SkScalar kScale = 100.f;
624     static constexpr SkScalar kIntervals[] = {10/kScale, 5/kScale};
625     paint.setPathEffect(SkDashPathEffect::Make(kIntervals, std::size(kIntervals), 0.f));
626     paint.setAntiAlias(true);
627     paint.setStrokeWidth(0.25f/kScale);
628     // substep moves the subpixel offset every iteration.
629     static constexpr SkScalar kSubstep = 0.05f/kScale;
630     // We will draw a grid of horiz/vertical lines that pass through each other's off intervals.
631     static constexpr SkScalar kStep = kIntervals[0] + kIntervals[1];
632     canvas->scale(kScale, kScale);
633     canvas->translate(kIntervals[1], kIntervals[1]);
634     for (auto c : {SkPaint::kButt_Cap, SkPaint::kSquare_Cap, SkPaint::kRound_Cap}) {
635         paint.setStrokeCap(c);
636         for (SkScalar x = -.5f*kIntervals[1]; x < 105/kScale; x += (kStep + kSubstep)) {
637             canvas->drawLine({x, 0}, {x, 100/kScale}, paint);
638             canvas->drawLine({0, x}, {100/kScale, x}, paint);
639         }
640         canvas->translate(110/kScale, 0);
641     }
642 }
643 
644 DEF_SIMPLE_GM(path_effect_empty_result, canvas, 100, 100) {
645     SkPaint p;
646     p.setStroke(true);
647     p.setStrokeWidth(1);
648 
649     SkPath path;
650     float r = 70;
651     float l = 70;
652     float t = 70;
653     float b = 70;
654     path.moveTo(l, t);
655     path.lineTo(r, t);
656     path.lineTo(r, b);
657     path.lineTo(l, b);
658     path.close();
659 
660     float dashes[] = {2.f, 2.f};
661     p.setPathEffect(SkDashPathEffect::Make(dashes, 2, 0.f));
662 
663     canvas->drawPath(path, p);
664 }
665 
666 //////////////////////////////////////////////////////////////////////////////
667 
668 DEF_GM(return new DashingGM;)
669 DEF_GM(return new Dashing2GM;)
670 DEF_GM(return new Dashing3GM;)
671 DEF_GM(return new Dashing4GM;)
672 DEF_GM(return new Dashing5GM(true);)
673 DEF_GM(return new Dashing5GM(false);)
674