aboutsummaryrefslogtreecommitdiffhomepage
path: root/src/core/SkScan_Hairline.cpp
blob: 083dc0df5f8d93a21be95b5ec58c6cb52c63af9f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkScan.h"
#include "SkBlitter.h"
#include "SkMathPriv.h"
#include "SkRasterClip.h"
#include "SkFDot6.h"
#include "SkLineClipper.h"

static void horiline(int x, int stopx, SkFixed fy, SkFixed dy,
                     SkBlitter* blitter) {
    SkASSERT(x < stopx);

    do {
        blitter->blitH(x, fy >> 16, 1);
        fy += dy;
    } while (++x < stopx);
}

static void vertline(int y, int stopy, SkFixed fx, SkFixed dx,
                     SkBlitter* blitter) {
    SkASSERT(y < stopy);

    do {
        blitter->blitH(fx >> 16, y, 1);
        fx += dx;
    } while (++y < stopy);
}

#ifdef SK_DEBUG
static bool canConvertFDot6ToFixed(SkFDot6 x) {
    const int maxDot6 = SK_MaxS32 >> (16 - 6);
    return SkAbs32(x) <= maxDot6;
}
#endif

void SkScan::HairLineRgn(const SkPoint array[], int arrayCount, const SkRegion* clip,
                         SkBlitter* origBlitter) {
    SkBlitterClipper    clipper;
    SkIRect clipR, ptsR;

    const SkScalar max = SkIntToScalar(32767);
    const SkRect fixedBounds = SkRect::MakeLTRB(-max, -max, max, max);

    SkRect clipBounds;
    if (clip) {
        clipBounds.set(clip->getBounds());
    }

    for (int i = 0; i < arrayCount - 1; ++i) {
        SkBlitter* blitter = origBlitter;

        SkPoint pts[2];

        // We have to pre-clip the line to fit in a SkFixed, so we just chop
        // the line. TODO find a way to actually draw beyond that range.
        if (!SkLineClipper::IntersectLine(&array[i], fixedBounds, pts)) {
            continue;
        }

        // Perform a clip in scalar space, so we catch huge values which might
        // be missed after we convert to SkFDot6 (overflow)
        if (clip && !SkLineClipper::IntersectLine(pts, clipBounds, pts)) {
            continue;
        }

        SkFDot6 x0 = SkScalarToFDot6(pts[0].fX);
        SkFDot6 y0 = SkScalarToFDot6(pts[0].fY);
        SkFDot6 x1 = SkScalarToFDot6(pts[1].fX);
        SkFDot6 y1 = SkScalarToFDot6(pts[1].fY);

        SkASSERT(canConvertFDot6ToFixed(x0));
        SkASSERT(canConvertFDot6ToFixed(y0));
        SkASSERT(canConvertFDot6ToFixed(x1));
        SkASSERT(canConvertFDot6ToFixed(y1));

        if (clip) {
            // now perform clipping again, as the rounding to dot6 can wiggle us
            // our rects are really dot6 rects, but since we've already used
            // lineclipper, we know they will fit in 32bits (26.6)
            const SkIRect& bounds = clip->getBounds();

            clipR.set(SkIntToFDot6(bounds.fLeft), SkIntToFDot6(bounds.fTop),
                      SkIntToFDot6(bounds.fRight), SkIntToFDot6(bounds.fBottom));
            ptsR.set(x0, y0, x1, y1);
            ptsR.sort();

            // outset the right and bottom, to account for how hairlines are
            // actually drawn, which may hit the pixel to the right or below of
            // the coordinate
            ptsR.fRight += SK_FDot6One;
            ptsR.fBottom += SK_FDot6One;

            if (!SkIRect::Intersects(ptsR, clipR)) {
                continue;
            }
            if (!clip->isRect() || !clipR.contains(ptsR)) {
                blitter = clipper.apply(origBlitter, clip);
            }
        }

        SkFDot6 dx = x1 - x0;
        SkFDot6 dy = y1 - y0;

        if (SkAbs32(dx) > SkAbs32(dy)) { // mostly horizontal
            if (x0 > x1) {   // we want to go left-to-right
                SkTSwap<SkFDot6>(x0, x1);
                SkTSwap<SkFDot6>(y0, y1);
            }
            int ix0 = SkFDot6Round(x0);
            int ix1 = SkFDot6Round(x1);
            if (ix0 == ix1) {// too short to draw
                continue;
            }

            SkFixed slope = SkFixedDiv(dy, dx);
            SkFixed startY = SkFDot6ToFixed(y0) + (slope * ((32 - x0) & 63) >> 6);

            horiline(ix0, ix1, startY, slope, blitter);
        } else {              // mostly vertical
            if (y0 > y1) {   // we want to go top-to-bottom
                SkTSwap<SkFDot6>(x0, x1);
                SkTSwap<SkFDot6>(y0, y1);
            }
            int iy0 = SkFDot6Round(y0);
            int iy1 = SkFDot6Round(y1);
            if (iy0 == iy1) { // too short to draw
                continue;
            }

            SkFixed slope = SkFixedDiv(dx, dy);
            SkFixed startX = SkFDot6ToFixed(x0) + (slope * ((32 - y0) & 63) >> 6);

            vertline(iy0, iy1, startX, slope, blitter);
        }
    }
}

// we don't just draw 4 lines, 'cause that can leave a gap in the bottom-right
// and double-hit the top-left.
// TODO: handle huge coordinates on rect (before calling SkScalarToFixed)
void SkScan::HairRect(const SkRect& rect, const SkRasterClip& clip,
                      SkBlitter* blitter) {
    SkAAClipBlitterWrapper wrapper;
    SkBlitterClipper    clipper;
    SkIRect             r;

    r.set(SkScalarToFixed(rect.fLeft) >> 16,
          SkScalarToFixed(rect.fTop) >> 16,
          (SkScalarToFixed(rect.fRight) >> 16) + 1,
          (SkScalarToFixed(rect.fBottom) >> 16) + 1);

    if (clip.quickReject(r)) {
        return;
    }
    if (!clip.quickContains(r)) {
        const SkRegion* clipRgn;
        if (clip.isBW()) {
            clipRgn = &clip.bwRgn();
        } else {
            wrapper.init(clip, blitter);
            clipRgn = &wrapper.getRgn();
            blitter = wrapper.getBlitter();
        }
        blitter = clipper.apply(blitter, clipRgn);
    }

    int width = r.width();
    int height = r.height();

    if ((width | height) == 0) {
        return;
    }
    if (width <= 2 || height <= 2) {
        blitter->blitRect(r.fLeft, r.fTop, width, height);
        return;
    }
    // if we get here, we know we have 4 segments to draw
    blitter->blitH(r.fLeft, r.fTop, width);                     // top
    blitter->blitRect(r.fLeft, r.fTop + 1, 1, height - 2);      // left
    blitter->blitRect(r.fRight - 1, r.fTop + 1, 1, height - 2); // right
    blitter->blitH(r.fLeft, r.fBottom - 1, width);              // bottom
}

///////////////////////////////////////////////////////////////////////////////

#include "SkPath.h"
#include "SkGeometry.h"
#include "SkNx.h"

#define kMaxCubicSubdivideLevel 9
#define kMaxQuadSubdivideLevel  5

static int compute_int_quad_dist(const SkPoint pts[3]) {
    // compute the vector between the control point ([1]) and the middle of the
    // line connecting the start and end ([0] and [2])
    SkScalar dx = SkScalarHalf(pts[0].fX + pts[2].fX) - pts[1].fX;
    SkScalar dy = SkScalarHalf(pts[0].fY + pts[2].fY) - pts[1].fY;
    // we want everyone to be positive
    dx = SkScalarAbs(dx);
    dy = SkScalarAbs(dy);
    // convert to whole pixel values (use ceiling to be conservative)
    int idx = SkScalarCeilToInt(dx);
    int idy = SkScalarCeilToInt(dy);
    // use the cheap approx for distance
    if (idx > idy) {
        return idx + (idy >> 1);
    } else {
        return idy + (idx >> 1);
    }
}

static void hair_quad(const SkPoint pts[3], const SkRegion* clip,
                     SkBlitter* blitter, int level, SkScan::HairRgnProc lineproc) {
    SkASSERT(level <= kMaxQuadSubdivideLevel);

    SkQuadCoeff coeff(pts);

    const int lines = 1 << level;
    Sk2s t(0);
    Sk2s dt(SK_Scalar1 / lines);

    SkPoint tmp[(1 << kMaxQuadSubdivideLevel) + 1];
    SkASSERT((unsigned)lines < SK_ARRAY_COUNT(tmp));

    tmp[0] = pts[0];
    Sk2s A = coeff.fA;
    Sk2s B = coeff.fB;
    Sk2s C = coeff.fC;
    for (int i = 1; i < lines; ++i) {
        t = t + dt;
        ((A * t + B) * t + C).store(&tmp[i]);
    }
    tmp[lines] = pts[2];
    lineproc(tmp, lines + 1, clip, blitter);
}

static SkRect compute_nocheck_quad_bounds(const SkPoint pts[3]) {
    SkASSERT(SkScalarsAreFinite(&pts[0].fX, 6));

    Sk2s min = Sk2s::Load(pts);
    Sk2s max = min;
    for (int i = 1; i < 3; ++i) {
        Sk2s pair = Sk2s::Load(pts+i);
        min = Sk2s::Min(min, pair);
        max = Sk2s::Max(max, pair);
    }
    return { min[0], min[1], max[0], max[1] };
}

static bool is_inverted(const SkRect& r) {
    return r.fLeft > r.fRight || r.fTop > r.fBottom;
}

// Can't call SkRect::intersects, since it cares about empty, and we don't (since we tracking
// something to be stroked, so empty can still draw something (e.g. horizontal line)
static bool geometric_overlap(const SkRect& a, const SkRect& b) {
    SkASSERT(!is_inverted(a) && !is_inverted(b));
    return a.fLeft < b.fRight && b.fLeft < a.fRight &&
            a.fTop < b.fBottom && b.fTop < a.fBottom;
}

// Can't call SkRect::contains, since it cares about empty, and we don't (since we tracking
// something to be stroked, so empty can still draw something (e.g. horizontal line)
static bool geometric_contains(const SkRect& outer, const SkRect& inner) {
    SkASSERT(!is_inverted(outer) && !is_inverted(inner));
    return inner.fRight <= outer.fRight && inner.fLeft >= outer.fLeft &&
            inner.fBottom <= outer.fBottom && inner.fTop >= outer.fTop;
}

static inline void hairquad(const SkPoint pts[3], const SkRegion* clip, const SkRect* insetClip, const SkRect* outsetClip,
    SkBlitter* blitter, int level, SkScan::HairRgnProc lineproc) {
    if (insetClip) {
        SkASSERT(outsetClip);
        SkRect bounds = compute_nocheck_quad_bounds(pts);
        if (!geometric_overlap(*outsetClip, bounds)) {
            return;
        } else if (geometric_contains(*insetClip, bounds)) {
            clip = nullptr;
        }
    }

    hair_quad(pts, clip, blitter, level, lineproc);
}

static inline Sk2s abs(const Sk2s& value) {
    return Sk2s::Max(value, Sk2s(0)-value);
}

static inline SkScalar max_component(const Sk2s& value) {
    SkScalar components[2];
    value.store(components);
    return SkTMax(components[0], components[1]);
}

static inline int compute_cubic_segs(const SkPoint pts[4]) {
    Sk2s p0 = from_point(pts[0]);
    Sk2s p1 = from_point(pts[1]);
    Sk2s p2 = from_point(pts[2]);
    Sk2s p3 = from_point(pts[3]);

    const Sk2s oneThird(1.0f / 3.0f);
    const Sk2s twoThird(2.0f / 3.0f);

    Sk2s p13 = oneThird * p3 + twoThird * p0;
    Sk2s p23 = oneThird * p0 + twoThird * p3;

    SkScalar diff = max_component(Sk2s::Max(abs(p1 - p13), abs(p2 - p23)));
    SkScalar tol = SK_Scalar1 / 8;

    for (int i = 0; i < kMaxCubicSubdivideLevel; ++i) {
        if (diff < tol) {
            return 1 << i;
        }
        tol *= 4;
    }
    return 1 << kMaxCubicSubdivideLevel;
}

static bool lt_90(SkPoint p0, SkPoint pivot, SkPoint p2) {
    return SkVector::DotProduct(p0 - pivot, p2 - pivot) >= 0;
}

// The off-curve points are "inside" the limits of the on-curve pts
static bool quick_cubic_niceness_check(const SkPoint pts[4]) {
    return lt_90(pts[1], pts[0], pts[3]) &&
           lt_90(pts[2], pts[0], pts[3]) &&
           lt_90(pts[1], pts[3], pts[0]) &&
           lt_90(pts[2], pts[3], pts[0]);
}

static void hair_cubic(const SkPoint pts[4], const SkRegion* clip, SkBlitter* blitter,
                       SkScan::HairRgnProc lineproc) {
    const int lines = compute_cubic_segs(pts);
    SkASSERT(lines > 0);
    if (1 == lines) {
        SkPoint tmp[2] = { pts[0], pts[3] };
        lineproc(tmp, 2, clip, blitter);
        return;
    }

    SkCubicCoeff coeff(pts);

    const Sk2s dt(SK_Scalar1 / lines);
    Sk2s t(0);

    SkPoint tmp[(1 << kMaxCubicSubdivideLevel) + 1];
    SkASSERT((unsigned)lines < SK_ARRAY_COUNT(tmp));

    tmp[0] = pts[0];
    Sk2s A = coeff.fA;
    Sk2s B = coeff.fB;
    Sk2s C = coeff.fC;
    Sk2s D = coeff.fD;
    for (int i = 1; i < lines; ++i) {
        t = t + dt;
        (((A * t + B) * t + C) * t + D).store(&tmp[i]);
    }
    tmp[lines] = pts[3];
    lineproc(tmp, lines + 1, clip, blitter);
}

static SkRect compute_nocheck_cubic_bounds(const SkPoint pts[4]) {
    SkASSERT(SkScalarsAreFinite(&pts[0].fX, 8));

    Sk2s min = Sk2s::Load(pts);
    Sk2s max = min;
    for (int i = 1; i < 4; ++i) {
        Sk2s pair = Sk2s::Load(pts+i);
        min = Sk2s::Min(min, pair);
        max = Sk2s::Max(max, pair);
    }
    return { min[0], min[1], max[0], max[1] };
}

static inline void haircubic(const SkPoint pts[4], const SkRegion* clip, const SkRect* insetClip, const SkRect* outsetClip,
                      SkBlitter* blitter, int level, SkScan::HairRgnProc lineproc) {
    if (insetClip) {
        SkASSERT(outsetClip);
        SkRect bounds = compute_nocheck_cubic_bounds(pts);
        if (!geometric_overlap(*outsetClip, bounds)) {
            return;
        } else if (geometric_contains(*insetClip, bounds)) {
            clip = nullptr;
        }
    }

    if (quick_cubic_niceness_check(pts)) {
        hair_cubic(pts, clip, blitter, lineproc);
    } else {
        SkPoint  tmp[13];
        SkScalar tValues[3];

        int count = SkChopCubicAtMaxCurvature(pts, tmp, tValues);
        for (int i = 0; i < count; i++) {
            hair_cubic(&tmp[i * 3], clip, blitter, lineproc);
        }
    }
}

static int compute_quad_level(const SkPoint pts[3]) {
    int d = compute_int_quad_dist(pts);
    /*  quadratics approach the line connecting their start and end points
     4x closer with each subdivision, so we compute the number of
     subdivisions to be the minimum need to get that distance to be less
     than a pixel.
     */
    int level = (33 - SkCLZ(d)) >> 1;
    // sanity check on level (from the previous version)
    if (level > kMaxQuadSubdivideLevel) {
        level = kMaxQuadSubdivideLevel;
    }
    return level;
}

/* Extend the points in the direction of the starting or ending tangent by 1/2 unit to
   account for a round or square cap. If there's no distance between the end point and
   the control point, use the next control point to create a tangent. If the curve
   is degenerate, move the cap out 1/2 unit horizontally. */
template <SkPaint::Cap capStyle>
void extend_pts(SkPath::Verb prevVerb, SkPath::Verb nextVerb, SkPoint* pts, int ptCount) {
    SkASSERT(SkPaint::kSquare_Cap == capStyle || SkPaint::kRound_Cap == capStyle);
    // The area of a circle is PI*R*R. For a unit circle, R=1/2, and the cap covers half of that.
    const SkScalar capOutset = SkPaint::kSquare_Cap == capStyle ? 0.5f : SK_ScalarPI / 8;
    if (SkPath::kMove_Verb == prevVerb) {
        SkPoint* first = pts;
        SkPoint* ctrl = first;
        int controls = ptCount - 1;
        SkVector tangent;
        do {
            tangent = *first - *++ctrl;
        } while (tangent.isZero() && --controls > 0);
        if (tangent.isZero()) {
            tangent.set(1, 0);
            controls = ptCount - 1;  // If all points are equal, move all but one
        } else {
            tangent.normalize();
        }
        do {    // If the end point and control points are equal, loop to move them in tandem.
            first->fX += tangent.fX * capOutset;
            first->fY += tangent.fY * capOutset;
            ++first;
        } while (++controls < ptCount);
    }
    if (SkPath::kMove_Verb == nextVerb || SkPath::kDone_Verb == nextVerb) {
        SkPoint* last = &pts[ptCount - 1];
        SkPoint* ctrl = last;
        int controls = ptCount - 1;
        SkVector tangent;
        do {
            tangent = *last - *--ctrl;
        } while (tangent.isZero() && --controls > 0);
        if (tangent.isZero()) {
            tangent.set(-1, 0);
            controls = ptCount - 1;
        } else {
            tangent.normalize();
        }
        do {
            last->fX += tangent.fX * capOutset;
            last->fY += tangent.fY * capOutset;
            --last;
        } while (++controls < ptCount);
    }
}

template <SkPaint::Cap capStyle>
void hair_path(const SkPath& path, const SkRasterClip& rclip, SkBlitter* blitter,
                      SkScan::HairRgnProc lineproc) {
    if (path.isEmpty()) {
        return;
    }

    SkAAClipBlitterWrapper wrap;
    const SkRegion* clip = nullptr;
    SkRect insetStorage, outsetStorage;
    const SkRect* insetClip = nullptr;
    const SkRect* outsetClip = nullptr;

    {
        const int capOut = SkPaint::kButt_Cap == capStyle ? 1 : 2;
        const SkIRect ibounds = path.getBounds().roundOut().makeOutset(capOut, capOut);
        if (rclip.quickReject(ibounds)) {
            return;
        }
        if (!rclip.quickContains(ibounds)) {
            if (rclip.isBW()) {
                clip = &rclip.bwRgn();
            } else {
                wrap.init(rclip, blitter);
                blitter = wrap.getBlitter();
                clip = &wrap.getRgn();
            }

            /*
             *  We now cache two scalar rects, to use for culling per-segment (e.g. cubic).
             *  Since we're hairlining, the "bounds" of the control points isn't necessairly the
             *  limit of where a segment can draw (it might draw up to 1 pixel beyond in aa-hairs).
             *
             *  Compute the pt-bounds per segment is easy, so we do that, and then inversely adjust
             *  the culling bounds so we can just do a straight compare per segment.
             *
             *  insetClip is use for quick-accept (i.e. the segment is not clipped), so we inset
             *  it from the clip-bounds (since segment bounds can be off by 1).
             *
             *  outsetClip is used for quick-reject (i.e. the segment is entirely outside), so we
             *  outset it from the clip-bounds.
             */
            insetStorage.set(clip->getBounds());
            outsetStorage = insetStorage.makeOutset(1, 1);
            insetStorage.inset(1, 1);
            if (is_inverted(insetStorage)) {
                /*
                 *  our bounds checks assume the rects are never inverted. If insetting has
                 *  created that, we assume that the area is too small to safely perform a
                 *  quick-accept, so we just mark the rect as empty (so the quick-accept check
                 *  will always fail.
                 */
                insetStorage.setEmpty();    // just so we don't pass an inverted rect
            }
            if (rclip.isRect()) {
                insetClip = &insetStorage;
            }
            outsetClip = &outsetStorage;
        }
    }

    SkPath::RawIter     iter(path);
    SkPoint             pts[4], firstPt, lastPt;
    SkPath::Verb        verb, prevVerb;
    SkAutoConicToQuads  converter;

    if (SkPaint::kButt_Cap != capStyle) {
        prevVerb = SkPath::kDone_Verb;
    }
    while ((verb = iter.next(pts)) != SkPath::kDone_Verb) {
        switch (verb) {
            case SkPath::kMove_Verb:
                firstPt = lastPt = pts[0];
                break;
            case SkPath::kLine_Verb:
                if (SkPaint::kButt_Cap != capStyle) {
                    extend_pts<capStyle>(prevVerb, iter.peek(), pts, 2);
                }
                lineproc(pts, 2, clip, blitter);
                lastPt = pts[1];
                break;
            case SkPath::kQuad_Verb:
                if (SkPaint::kButt_Cap != capStyle) {
                    extend_pts<capStyle>(prevVerb, iter.peek(), pts, 3);
                }
                hairquad(pts, clip, insetClip, outsetClip, blitter, compute_quad_level(pts), lineproc);
                lastPt = pts[2];
                break;
            case SkPath::kConic_Verb: {
                if (SkPaint::kButt_Cap != capStyle) {
                    extend_pts<capStyle>(prevVerb, iter.peek(), pts, 3);
                }
                // how close should the quads be to the original conic?
                const SkScalar tol = SK_Scalar1 / 4;
                const SkPoint* quadPts = converter.computeQuads(pts,
                                                       iter.conicWeight(), tol);
                for (int i = 0; i < converter.countQuads(); ++i) {
                    int level = compute_quad_level(quadPts);
                    hairquad(quadPts, clip, insetClip, outsetClip, blitter, level, lineproc);
                    quadPts += 2;
                }
                lastPt = pts[2];
                break;
            }
            case SkPath::kCubic_Verb: {
                if (SkPaint::kButt_Cap != capStyle) {
                    extend_pts<capStyle>(prevVerb, iter.peek(), pts, 4);
                }
                haircubic(pts, clip, insetClip, outsetClip, blitter, kMaxCubicSubdivideLevel, lineproc);
                lastPt = pts[3];
            } break;
            case SkPath::kClose_Verb:
                pts[0] = lastPt;
                pts[1] = firstPt;
                if (SkPaint::kButt_Cap != capStyle && prevVerb == SkPath::kMove_Verb) {
                    // cap moveTo/close to match svg expectations for degenerate segments
                    extend_pts<capStyle>(prevVerb, iter.peek(), pts, 2);
                }
                lineproc(pts, 2, clip, blitter);
                break;
            case SkPath::kDone_Verb:
                break;
        }
        if (SkPaint::kButt_Cap != capStyle) {
            prevVerb = verb;
        }
    }
}

void SkScan::HairPath(const SkPath& path, const SkRasterClip& clip, SkBlitter* blitter) {
    hair_path<SkPaint::kButt_Cap>(path, clip, blitter, SkScan::HairLineRgn);
}

void SkScan::AntiHairPath(const SkPath& path, const SkRasterClip& clip, SkBlitter* blitter) {
    hair_path<SkPaint::kButt_Cap>(path, clip, blitter, SkScan::AntiHairLineRgn);
}

void SkScan::HairSquarePath(const SkPath& path, const SkRasterClip& clip, SkBlitter* blitter) {
    hair_path<SkPaint::kSquare_Cap>(path, clip, blitter, SkScan::HairLineRgn);
}

void SkScan::AntiHairSquarePath(const SkPath& path, const SkRasterClip& clip, SkBlitter* blitter) {
    hair_path<SkPaint::kSquare_Cap>(path, clip, blitter, SkScan::AntiHairLineRgn);
}

void SkScan::HairRoundPath(const SkPath& path, const SkRasterClip& clip, SkBlitter* blitter) {
    hair_path<SkPaint::kRound_Cap>(path, clip, blitter, SkScan::HairLineRgn);
}

void SkScan::AntiHairRoundPath(const SkPath& path, const SkRasterClip& clip, SkBlitter* blitter) {
    hair_path<SkPaint::kRound_Cap>(path, clip, blitter, SkScan::AntiHairLineRgn);
}

///////////////////////////////////////////////////////////////////////////////

void SkScan::FrameRect(const SkRect& r, const SkPoint& strokeSize,
                       const SkRasterClip& clip, SkBlitter* blitter) {
    SkASSERT(strokeSize.fX >= 0 && strokeSize.fY >= 0);

    if (strokeSize.fX < 0 || strokeSize.fY < 0) {
        return;
    }

    const SkScalar dx = strokeSize.fX;
    const SkScalar dy = strokeSize.fY;
    SkScalar rx = SkScalarHalf(dx);
    SkScalar ry = SkScalarHalf(dy);
    SkRect   outer, tmp;

    outer.set(r.fLeft - rx, r.fTop - ry,
                r.fRight + rx, r.fBottom + ry);

    if (r.width() <= dx || r.height() <= dy) {
        SkScan::FillRect(outer, clip, blitter);
        return;
    }

    tmp.set(outer.fLeft, outer.fTop, outer.fRight, outer.fTop + dy);
    SkScan::FillRect(tmp, clip, blitter);
    tmp.fTop = outer.fBottom - dy;
    tmp.fBottom = outer.fBottom;
    SkScan::FillRect(tmp, clip, blitter);

    tmp.set(outer.fLeft, outer.fTop + dy, outer.fLeft + dx, outer.fBottom - dy);
    SkScan::FillRect(tmp, clip, blitter);
    tmp.fLeft = outer.fRight - dx;
    tmp.fRight = outer.fRight;
    SkScan::FillRect(tmp, clip, blitter);
}

void SkScan::HairLine(const SkPoint pts[], int count, const SkRasterClip& clip,
                      SkBlitter* blitter) {
    if (clip.isBW()) {
        HairLineRgn(pts, count, &clip.bwRgn(), blitter);
    } else {
        const SkRegion* clipRgn = nullptr;

        SkRect r;
        r.set(pts, count);
        r.outset(SK_ScalarHalf, SK_ScalarHalf);

        SkAAClipBlitterWrapper wrap;
        if (!clip.quickContains(r.roundOut())) {
            wrap.init(clip, blitter);
            blitter = wrap.getBlitter();
            clipRgn = &wrap.getRgn();
        }
        HairLineRgn(pts, count, clipRgn, blitter);
    }
}

void SkScan::AntiHairLine(const SkPoint pts[], int count, const SkRasterClip& clip,
                          SkBlitter* blitter) {
    if (clip.isBW()) {
        AntiHairLineRgn(pts, count, &clip.bwRgn(), blitter);
    } else {
        const SkRegion* clipRgn = nullptr;

        SkRect r;
        r.set(pts, count);

        SkAAClipBlitterWrapper wrap;
        if (!clip.quickContains(r.roundOut().makeOutset(1, 1))) {
            wrap.init(clip, blitter);
            blitter = wrap.getBlitter();
            clipRgn = &wrap.getRgn();
        }
        AntiHairLineRgn(pts, count, clipRgn, blitter);
    }
}