internal/stroke: add BenchmarkSplitCubic

Signed-off-by: Egon Elbre <egonelbre@gmail.com>

internal/stroke/stroke_test.go

@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package stroke
+
+import (
+	"strconv"
+	"testing"
+
+	"gioui.org/internal/f32"
+)
+
+func BenchmarkSplitCubic(b *testing.B) {
+	type scenario struct {
+		segments               int
+		from, ctrl0, ctrl1, to f32.Point
+	}
+
+	scenarios := []scenario{
+		{
+			segments: 4,
+			from:     f32.Pt(0, 0),
+			ctrl0:    f32.Pt(10, 10),
+			ctrl1:    f32.Pt(10, 10),
+			to:       f32.Pt(20, 0),
+		},
+		{
+			segments: 8,
+			from:     f32.Pt(-145.90305, 703.21277),
+			ctrl0:    f32.Pt(-940.20215, 606.05994),
+			ctrl1:    f32.Pt(74.58341, 405.815),
+			to:       f32.Pt(104.35474, -241.543),
+		},
+		{
+			segments: 16,
+			from:     f32.Pt(770.35626, 639.77765),
+			ctrl0:    f32.Pt(735.57135, 545.07837),
+			ctrl1:    f32.Pt(286.7138, 853.7052),
+			to:       f32.Pt(286.7138, 890.5413),
+		},
+		{
+			segments: 33,
+			from:     f32.Pt(0, 0),
+			ctrl0:    f32.Pt(0, 0),
+			ctrl1:    f32.Pt(100, 100),
+			to:       f32.Pt(100, 100),
+		},
+	}
+
+	for _, s := range scenarios {
+		s := s
+		b.Run(strconv.Itoa(s.segments), func(b *testing.B) {
+			from, ctrl0, ctrl1, to := s.from, s.ctrl0, s.ctrl1, s.to
+			quads := make([]QuadSegment, s.segments)
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				quads = SplitCubic(from, ctrl0, ctrl1, to, quads[:0])
+			}
+			if len(quads) != s.segments {
+				// this is just for checking that we are benchmarking similar splits
+				// when splitting algorithm splits differently, then it's fine to adjust the
+				// parameters to give appropriate number of segments.
+				b.Fatalf("expected %d but got %d", s.segments, len(quads))
+			}
+		})
+	}
+}