Respecify SkCanvas::drawArc, consolidate conversion to SkPath, add GM for oddball drawArcs

Allows the arc to wind more than 360 degrees when useCenter is true, specs that nothing draws
if the oval is empty or the sweep angle is 0.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2281653002

Review-Url: https://codereview.chromium.org/2281653002

1 files changed, 85 insertions, 0 deletions

diff --git a/gm/circulararcs.cpp b/gm/circulararcs.cpp
index 290390a47f..148ee42169 100644
--- a/gm/circulararcs.cpp
+++ b/gm/circulararcs.cpp
@@ -7,6 +7,7 @@
 
 #include <functional>
 #include "SkCanvas.h"
+#include "SkDashPathEffect.h"
 #include "gm.h"
 
 static constexpr SkScalar kStarts[] = {0.f, 10.f, 30.f, 45.f, 90.f, 165.f, 180.f, 270.f};
@@ -125,3 +126,87 @@ DEF_ARC_GM(stroke_and_fill_round) {
     };
     draw_arcs(canvas, setStroke);
 }
+
+DEF_SIMPLE_GM(circular_arcs_weird, canvas, 1000, 400) {
+    static constexpr SkScalar kS = 50;
+    struct Arc {
+        SkRect   fOval;
+        SkScalar fStart;
+        SkScalar fSweep;
+    };
+    static const Arc noDrawArcs[] = {
+        // no sweep
+        {SkRect::MakeWH(kS, kS),  0,  0},
+        // empty rect in x
+        {SkRect::MakeWH(-kS, kS), 0, 90},
+        // empty rect in y
+        {SkRect::MakeWH(kS, -kS), 0, 90},
+        // empty rect in x and y
+        {SkRect::MakeWH( 0,   0), 0, 90},
+    };
+    static const Arc arcs[] = {
+        // large start
+        {SkRect::MakeWH(kS, kS),   810.f,   90.f},
+        // large negative start
+        {SkRect::MakeWH(kS, kS),  -810.f,   90.f},
+        // exactly 360 sweep
+        {SkRect::MakeWH(kS, kS),     0.f,  360.f},
+        // exactly -360 sweep
+        {SkRect::MakeWH(kS, kS),     0.f, -360.f},
+        // exactly 540 sweep
+        {SkRect::MakeWH(kS, kS),     0.f,  540.f},
+        // exactly -540 sweep
+        {SkRect::MakeWH(kS, kS),     0.f, -540.f},
+        // generic large sweep and large start
+        {SkRect::MakeWH(kS, kS),  1125.f,  990.f},
+    };
+    SkTArray<SkPaint> paints;
+    // fill
+    paints.push_back();
+    // stroke
+    paints.push_back().setStyle(SkPaint::kStroke_Style);
+    paints.back().setStrokeWidth(kS / 6.f);
+    // hairline
+    paints.push_back().setStyle(SkPaint::kStroke_Style);
+    paints.back().setStrokeWidth(0.f);
+    // stroke and fill
+    paints.push_back().setStyle(SkPaint::kStrokeAndFill_Style);
+    paints.back().setStrokeWidth(kS / 6.f);
+    // dash effect
+    paints.push_back().setStyle(SkPaint::kStroke_Style);
+    paints.back().setStrokeWidth(kS / 6.f);
+    static constexpr SkScalar kDashIntervals[] = {kS / 15, 2 * kS / 15};
+    paints.back().setPathEffect(SkDashPathEffect::Make(kDashIntervals, 2, 0.f));
+
+    canvas->translate(kPad, kPad);
+    // This loop should draw nothing.
+    for (auto arc : noDrawArcs) {
+        for (auto paint : paints) {
+            paint.setAntiAlias(true);
+            canvas->drawArc(arc.fOval, arc.fStart, arc.fSweep, false, paint);
+            canvas->drawArc(arc.fOval, arc.fStart, arc.fSweep, true, paint);
+        }
+    }
+
+    SkPaint linePaint;
+    linePaint.setAntiAlias(true);
+    linePaint.setColor(SK_ColorRED);
+    SkScalar midX   = SK_ARRAY_COUNT(arcs) * (kS + kPad) - kPad/2.f;
+    SkScalar height = paints.count() * (kS + kPad);
+    canvas->drawLine(midX, -kPad, midX, height, linePaint);
+
+    for (auto paint : paints) {
+        paint.setAntiAlias(true);
+        canvas->save();
+        for (auto arc : arcs) {
+            canvas->drawArc(arc.fOval, arc.fStart, arc.fSweep, false, paint);
+            canvas->translate(kS + kPad, 0.f);
+        }
+        for (auto arc : arcs) {
+            canvas->drawArc(arc.fOval, arc.fStart, arc.fSweep, true, paint);
+            canvas->translate(kS + kPad, 0.f);
+        }
+        canvas->restore();
+        canvas->translate(0, kS + kPad);
+    }
+}