draw optimizations

client/world/drawer_clear_state_test.go

@@ -0,0 +1,40 @@
+package world
+
+import (
+	"image/color"
+	"testing"
+
+	"github.com/fogleman/gg"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGGDrawer_ClearRectTo_DoesNotAffectStrokeState(t *testing.T) {
+	t.Parallel()
+
+	dc := gg.NewContext(40, 20)
+	d := &GGDrawer{DC: dc}
+
+	// Fill background to white.
+	d.ClearAllTo(color.RGBA{R: 255, G: 255, B: 255, A: 255})
+
+	// Configure stroke to red and draw first line.
+	d.SetStrokeColor(color.RGBA{R: 255, A: 255})
+	d.SetLineWidth(2)
+	d.AddLine(2, 5, 38, 5)
+	d.Stroke()
+
+	// Clear a rect in the middle with gray (must not affect stroke state).
+	d.ClearRectTo(10, 0, 20, 20, color.RGBA{R: 200, G: 200, B: 200, A: 255})
+
+	// Draw second line WITHOUT reapplying stroke style; it must still be red.
+	d.AddLine(2, 15, 38, 15)
+	d.Stroke()
+
+	img := dc.Image()
+
+	// Sample a pixel from the second line (y ~15). We expect red channel dominates.
+	r, g, b, a := img.At(20, 15).RGBA()
+	require.Greater(t, a, uint32(0), "pixel must not be fully transparent")
+	require.Greater(t, r, g, "expected red-ish pixel after ClearRectTo")
+	require.Greater(t, r, b, "expected red-ish pixel after ClearRectTo")
+}