Bug fix: only render one frame at a time in Sequence (#824)

render/sequence.go

@@ -65,6 +65,7 @@ func (s Sequence) Paint(dc *gg.Context, bounds image.Rectangle, frameIdx int) {
 			dc.Push()
 			c.Paint(dc, bounds, frameIdx-fc)
 			dc.Pop()
+			break
 		}
 
 		fc += c.FrameCount()

render/sequence_test.go

@@ -0,0 +1,166 @@
+package render
+
+import (
+	"image"
+	"image/color"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSequenceOnlyOneFrameAtATime(t *testing.T) {
+	seq := Sequence{
+		Children: []Widget{
+			Box{Width: 3, Height: 3, Color: color.RGBA{0xff, 0, 0, 0xff}},
+			Box{Width: 6, Height: 3, Color: color.RGBA{0, 0xff, 0, 0xff}},
+			Box{Width: 9, Height: 3, Color: color.RGBA{0, 0, 0xff, 0xff}},
+		},
+	}
+
+	// Frame 0
+	im := PaintWidget(seq, image.Rect(0, 0, 10, 3), 0)
+	assert.Equal(t, nil, checkImage([]string{
+		"rrr",
+		"rrr",
+		"rrr",
+	}, im))
+
+	// Frame 1
+	im = PaintWidget(seq, image.Rect(0, 0, 10, 3), 1)
+	assert.Equal(t, nil, checkImage([]string{
+		"gggggg",
+		"gggggg",
+		"gggggg",
+	}, im))
+
+	// Frame 2
+	im = PaintWidget(seq, image.Rect(0, 0, 10, 3), 2)
+	assert.Equal(t, nil, checkImage([]string{
+		"bbbbbbbbb",
+		"bbbbbbbbb",
+		"bbbbbbbbb",
+	}, im))
+}
+
+func TestSequenceWithAnimatedChildren(t *testing.T) {
+	// Returns a 2x2 grid with background color, and a single
+	// pixel of foreground color at x,y.
+	frame := func(x, y int, fg color.Color, bg color.Color) Widget {
+		row0 := Row{
+			Children: []Widget{
+				Box{Width: 1, Height: 1, Color: bg},
+				Box{Width: 1, Height: 1, Color: bg},
+			},
+		}
+		row1 := Row{
+			Children: []Widget{
+				Box{Width: 1, Height: 1, Color: bg},
+				Box{Width: 1, Height: 1, Color: bg},
+			},
+		}
+		if y == 0 {
+			row0.Children[x] = Box{Width: 1, Height: 1, Color: fg}
+		} else {
+			row1.Children[x] = Box{Width: 1, Height: 1, Color: fg}
+		}
+		return Column{
+			Children: []Widget{row0, row1},
+		}
+	}
+
+	black := color.RGBA{0, 0, 0, 0}
+	red := color.RGBA{0xff, 0, 0, 0xff}
+	green := color.RGBA{0, 0xff, 0, 0xff}
+	blue := color.RGBA{0, 0, 0xff, 0xff}
+
+	anim0 := Animation{
+		Children: []Widget{
+			frame(0, 0, red, black),
+			frame(1, 0, red, black),
+			frame(1, 1, red, black),
+			frame(0, 1, red, black),
+		},
+	}
+	anim1 := Animation{
+		Children: []Widget{
+			frame(0, 0, green, black),
+			frame(1, 0, green, black),
+			frame(1, 1, green, black),
+			frame(0, 1, green, black),
+		},
+	}
+	anim2 := Animation{
+		Children: []Widget{
+			frame(0, 0, blue, black),
+			frame(1, 0, blue, black),
+			frame(1, 1, blue, black),
+			frame(0, 1, blue, black),
+		},
+	}
+
+	seq := Sequence{
+		Children: []Widget{
+			anim0,
+			anim1,
+			anim2,
+		},
+	}
+
+	assert.Equal(t, 12, seq.FrameCount())
+
+	expected := [][]string{
+		{
+			"r.",
+			"..",
+		},
+		{
+			".r",
+			"..",
+		},
+		{
+			"..",
+			".r",
+		},
+		{
+			"..",
+			"r.",
+		},
+		{
+			"g.",
+			"..",
+		},
+		{
+			".g",
+			"..",
+		},
+		{
+			"..",
+			".g",
+		},
+		{
+			"..",
+			"g.",
+		},
+		{
+			"b.",
+			"..",
+		},
+		{
+			".b",
+			"..",
+		},
+		{
+			"..",
+			".b",
+		},
+		{
+			"..",
+			"b.",
+		},
+	}
+
+	for i := 0; i < seq.FrameCount(); i++ {
+		im := PaintWidget(seq, image.Rect(0, 0, 2, 2), i)
+		assert.Equal(t, nil, checkImage(expected[i], im))
+	}
+}