feat: more or less fixed the parenting.

cmd/test/debug.go

@@ -22,7 +22,14 @@ func (d *Debug) Draw(c *Context) {
 		"fps: %d", int(c.FPS()),
 	))
 	keyStrs = append(keyStrs, fmt.Sprintf(
-		"absPlayerPos: %v", player.Position,
+		"relPlayerPos: %v", player.Position,
+	))
+	keyStrs = append(keyStrs, fmt.Sprintf(
+		"absPlayerPos: %v", player.AbsPosition(),
+	))
+
+	keyStrs = append(keyStrs, fmt.Sprintf(
+		"relTriPos: %v", tri.Position,
 	))
 	keyStrs = append(keyStrs, fmt.Sprintf(
 		"absTriPos: %v", tri.AbsPosition(),

cmd/test/player.go

@@ -19,7 +19,7 @@ func NewPlayer() *Player {
 	ret.Transform = gg.T()
 	fmt.Println("transform:", ret.Transform)
 	//ret.Parent = rect
-	ret.Scale = gg.V(5, 5)
+	ret.Scale = gg.V2(1)
 	// Around center.
 	ret.Around = gg.V2(.5)
 	ret.MoveSpeed =  90.
@@ -136,7 +136,7 @@ func (p *Player) Event(c *gg.Context) {
 		c.Camera.Position = pos.Sub(ec.Abs)
 	case *gg.WheelChange :
 		c.Camera.Scale = c.Camera.Scale.Add(gg.V2(
-			ec.Offset.Y * c.DT() * p.ScaleSpeed * 20,
+			ec.Offset.Y * c.DT() * p.ScaleSpeed * 40,
 		))
 	}
 

cmd/test/trianlge.go

@@ -1,7 +1,7 @@
 package main
 
 import "github.com/di4f/gg"
-//import "fmt"
+import "fmt"
 
 type Tri struct {
 	gg.DrawablePolygon
@@ -20,7 +20,7 @@ func NewTri() *Tri {
 			gg.V(0, -10),
 		},
 	}
-	ret.Color = gg.Color{gg.MaxColorV, gg.MaxColorV, 0, gg.MaxColorV}
+	ret.Color = gg.Rgba(1, 1, 0, 1)
 	ret.Visible = true
 	ret.Layer = TriangleL
 
@@ -51,3 +51,19 @@ func (t *Tri) Update(c *Context) {
 		)
 	}
 }
+
+func (t *Tri) Event(c *Context) {
+	switch e := c.Event.(type) {
+	case *gg.KeyDown :
+		if e.Key != gg.Key1 {
+			break
+		}
+		if t.Connected() {
+			fmt.Println("disconnecting:", tri.Transform)
+			t.Disconnect()
+		} else {
+			t.Connect(player)
+			fmt.Println("connecting:", tri.Transform)
+		}
+	}
+}

transform.go

@@ -55,26 +55,41 @@ func (t Transform) ScaledToY(y Float) Transform {
 }
 
 func (t *Transform) SetAbsPosition(absPosition Vector) {
-	m := t.Matrix()
+	if t.Parent == nil {
+		t.Position = absPosition
+		return
+	}
+	m := t.ParentMatrix()
 	m.Invert()
 	t.Position = absPosition.Apply(m)
 }
 
 // Get the absolute representation of the transform.
 func (t *Transform) Abs() Transform {
-	m := t.Matrix()
+	if t.Parent == nil {
-	ret := Transform{}
+		return *t
-	ret.Position = t.Position.Apply(m)
+	}
+
+	ret := T()
+	ret.Position = t.AbsPosition()
 	ret.Rotation = t.AbsRotation()
+	ret.Scale = t.AbsScale()
+
 	return ret
 }
 
 func (t *Transform) AbsPosition() Vector {
-	return t.Position.Apply(t.Matrix())
+	if t.Parent == nil {
+		return t.Position
+	}
+	return t.Position.Apply(t.ParentMatrix())
 }
 
 func (t *Transform) AbsScale() Vector {
-	return V2(0)
+	if t.Parent == nil {
+		return t.Scale
+	}
+	return V2(1)
 }
 
 func (t *Transform) AbsRotation() Float {
@@ -84,11 +99,23 @@ func (t *Transform) AbsRotation() Float {
 	return t.Rotation + t.Parent.GetTransform().AbsRotation()
 }
 
+func (t *Transform) SetAbsRotation(rot Float) {
+	if t.Parent == nil {
+		t.Rotation = rot
+	}
+	t.Rotation -= t.Parent.GetTransform().AbsRotation()
+}
+
 func (t *Transform) Connected() bool {
 	return t.Parent != nil
 }
 
-func (t *Transform) Connect(p Transformer) {
+func (t *Transform) Connect(parent Transformer) {
+	absPosition := t.AbsPosition()
+	absRotation := t.AbsRotation()
+	t.Parent = parent
+	t.SetAbsPosition(absPosition)
+	t.SetAbsRotation(absRotation)
 }
 
 func (t *Transform) Disconnect() {
@@ -96,7 +123,22 @@ func (t *Transform) Disconnect() {
 		return
 	}
 	*t = t.Abs()
-	t.Parent = nil
+}
+
+func (t *Transform) ParentMatrix() *Matrix {
+	g := &Matrix{}
+	if t.Parent == nil {
+		return g
+	}
+
+	p := t.Parent.GetTransform()
+	g = p.ParentMatrix()
+
+	g.Scale(p.Scale.X, p.Scale.Y)
+	g.Rotate(p.Rotation)
+	g.Translate(p.Position.X, p.Position.Y)
+
+	return g
 }
 
 // Returns the GeoM with corresponding
@@ -117,10 +159,8 @@ func (t *Transform)Matrix() *Matrix {
 	// And finally move to the absolute position.
 	g.Translate(t.Position.X, t.Position.Y)
 
-	if t.Parent != nil {
+	m := t.ParentMatrix()
-		m := t.Parent.GetTransform().Matrix()
 	g.Concat(*m)
-	}
 
 	return g
 }