feat: added the grid to the cmd/test.

bg.go

@@ -0,0 +1,3 @@
+package gg
+
+

cmd/test/main.go

@@ -12,12 +12,42 @@ import (
 
 type Context = gg.Context
 
+type Grid struct {
+	gg.Sprite
+	Cage, Width gg.Float
+}
+
+func (grid *Grid) Update(c *Context) {
+	//d := c.IsPressed(gg.KeyShift)
+	for _, ev := range c.Events { switch e := ev.(type){
+	case *gg.KeyDown : switch e.Key {
+	case gg.Key9 :
+		grid.Cage /= 10
+		grid.Width /= 5
+	case gg.Key0 :
+		grid.Cage *= 10
+		grid.Width *= 5
+	}}}
+}
+
+func (grid *Grid) Draw(c *Context) []gg.EVertex {
+	scale := c.Camera.Scale()
+	pos := c.Camera.Position()
+	grid.Uniforms["Zoom"] = gg.Float(scale.X)
+	grid.Uniforms["PosX"] = pos.X
+	grid.Uniforms["PosY"] = pos.Y
+	grid.Uniforms["Cage"] = grid.Cage
+	grid.Uniforms["Width"] = grid.Width
+	return grid.Sprite.Draw(c)
+}
+
 const (
 	HighestL gg.Layer = -iota
 	DebugL
 	TriangleL
 	PlayerL
 	RectL
+	BackgroundLayer
 	LowestL
 )
 
@@ -76,6 +106,50 @@ func main() {
 	circle.Visible = true*/
 	//e.Spawn(circle)
 
+	bgShader := gg.MustNewShader([]byte(`
+		package main
+
+		//kage:unit pixels
+
+		//var cameraScaleX, cameraScaleY
+		var Zoom float
+		var PosX, PosY float
+		var Cage float
+		var Width float
+
+		const (
+		)
+
+		func Fragment(dst vec4, src vec2, _ vec4) vec4 {
+			c := imageSrc0UnsafeAt(src)
+			dstSize := imageDstSize()/Zoom
+			absDst := vec2(
+				dst.x/Zoom - dstSize.x/2 - PosX,
+				dst.y/Zoom - dstSize.y/2 - PosY,
+			)
+			cx := c*step(Cage-Width, mod(absDst.x-Width/2, Cage))
+			cy := c*step(Cage-Width, mod(absDst.y-Width/2, Cage))
+			if cx.a == 0 {
+				return cy
+			}
+			return cx
+		}
+	`))
+	grid := &Grid{}
+	grid.Transform = gg.T()
+	grid.SetAround(gg.V2(0))
+	grid.Layer = BackgroundLayer
+	grid.Images[0] = gg.NewImage(720, 480)
+	grid.Images[0].Fill(gg.Rgba(1, 1, 1, 1))
+	grid.Shader = bgShader
+	grid.Uniforms = map[string] any{}
+	//bg.Floating = true
+	grid.Visible = true
+	grid.Floating = true
+	grid.Cage = 100
+	grid.Width = 5
+	e.Spawn(grid)
+
 	txt := &Text{}
 	txt.Transform = gg.T()
 	//txt.Position = gg.V2(400)