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fix circle dash

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Thin conic dashes are treated as lines both if the
curvature is detected as zero, and if the midpoint
is close enough to the control point.

To fix:
Halve the midpoint to control point magic number.
Use quad max curvature as a placeholder for conic
max curvature.

R=reed@google.com,fmalita@chromium.org
Bug:843966
Change-Id: Ide43bef8767c03670ffd19fdc38c191d6e2332f3
Reviewed-on: https://skia-review.googlesource.com/c/129243
Commit-Queue: Cary Clark <caryclark@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Cary Clark <caryclark@skia.org>
This commit is contained in:
Cary Clark 2018-12-04 14:52:40 -05:00 committed by Skia Commit-Bot
parent 7d1eb33aec
commit dbf2aec28a
2 changed files with 48 additions and 8 deletions
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36
gm/dashcircle.cpp
View File

@ -225,3 +225,39 @@ protected:
};
DEF_GM(return new DashCircle2GM;)
DEF_SIMPLE_GM(maddash, canvas, 1600, 1600) {
canvas->drawRect({0, 0, 1600, 1600}, SkPaint());
SkPaint p;
p.setColor(SK_ColorRED);
p.setAntiAlias(true);
p.setStyle(SkPaint::kStroke_Style);
p.setStrokeWidth(380);
SkScalar intvls[] = { 2.5, 10 /* 1200 */ };
p.setPathEffect(SkDashPathEffect::Make(intvls, 2, 0));
canvas->drawCircle(400, 400, 200, p);
SkPath path;
path.moveTo(800, 400);
path.quadTo(1000, 400, 1000, 600);
path.quadTo(1000, 800, 800, 800);
path.quadTo(600, 800, 600, 600);
path.quadTo(600, 400, 800, 400);
path.close();
canvas->translate(350, 150);
p.setStrokeWidth(320);
canvas->drawPath(path, p);
path.reset();
path.moveTo(800, 400);
path.cubicTo(900, 400, 1000, 500, 1000, 600);
path.cubicTo(1000, 700, 900, 800, 800, 800);
path.cubicTo(700, 800, 600, 700, 600, 600);
path.cubicTo(600, 500, 700, 400, 800, 400);
path.close();
canvas->translate(-550, 500);
p.setStrokeWidth(300);
canvas->drawPath(path, p);
}

20
src/core/SkStroke.cpp
View File

@ -591,7 +591,12 @@ static bool quad_in_line(const SkPoint quad[3]) {
SkASSERT(outer2 >= 1 && outer2 <= 2);
SkASSERT(outer1 < outer2);
int mid = outer1 ^ outer2 ^ 3;
SkScalar lineSlop = ptMax * ptMax * 0.00001f; // this multiplier is pulled out of the air
#ifdef SK_USE_LEGACY_CONIC_CURVATURE_SLOP
const float kCurvatureSlop = 0.00001f;
#else
const float kCurvatureSlop = 0.000005f; // this multiplier is pulled out of the air
#endif
SkScalar lineSlop = ptMax * ptMax * kCurvatureSlop;
return pt_to_line(quad[mid], quad[outer1], quad[outer2]) <= lineSlop;
}
@ -651,20 +656,19 @@ SkPathStroker::ReductionType SkPathStroker::CheckConicLinear(const SkConic& coni
if (!conic_in_line(conic)) {
return kQuad_ReductionType;
}
#if 0 // once findMaxCurvature is implemented, this will be a better solution
SkScalar t;
if (!conic.findMaxCurvature(&t) || 0 == t) {
return kLine_ReductionType;
}
#else // but for now, use extrema instead
#ifdef SK_USE_LEGACY_CONIC_CURVATURE_SLOP
SkScalar xT = 0, yT = 0;
(void) conic.findXExtrema(&xT);
(void) conic.findYExtrema(&yT);
SkScalar t = SkTMax(xT, yT);
#else
// SkFindConicMaxCurvature would be a better solution, once we know how to
// implement it. Quad curvature is a reasonable substitute
SkScalar t = SkFindQuadMaxCurvature(conic.fPts);
#endif
if (0 == t) {
return kLine_ReductionType;
}
#endif
conic.evalAt(t, reduction, nullptr);
return kDegenerate_ReductionType;
}