camera improvements

engine/camera.go

@@ -26,7 +26,16 @@ func (c *Camera) Scan() []interface{} { return []interface{}{c.Scene} }
 func (c *Camera) Prepare(game *Game) { c.game = game }
 
 func (c *Camera) Centre(p image.Point) {
+	// Currently the centre of the screen c is A^-1.c in world coordinates
+	// So it is off by (p - A^-1.c)
 	t := c.Transform.GeoM()
-	t.Reset()
-	t.Translate(float64(c.game.ScreenWidth/2-p.X), float64(c.game.ScreenHeight/2-p.Y))
+	t.Invert()
+	wcx, wcy := t.Apply(float64(c.game.ScreenWidth/2), float64(c.game.ScreenHeight/2))
+	t.Translate(float64(p.X)-wcx, float64(p.Y)-wcy)
+	t.Invert()
+}
+
+func (c *Camera) Zoom(f float64) {
+	t := c.Transform.GeoM()
+	t.Scale(f, f)
 }

game/aw.go

@@ -67,11 +67,22 @@ func (aw *Awakeman) Update() error {
 			aw.SetAnim(aw.animIdleLeft)
 		}
 	}
+	zc := false
+	if inpututil.IsKeyJustPressed(ebiten.KeyShift) {
+		aw.camera.Zoom(2)
+		zc = true
+	}
+	if inpututil.IsKeyJustReleased(ebiten.KeyShift) {
+		aw.camera.Zoom(0.5)
+		zc = true
+	}
+
+	p := aw.Pos
 	aw.MoveX(aw.vx, func() { aw.vx = -aw.vx * bounceDampen })
 	aw.MoveY(aw.vy, func() { aw.vy = -aw.vy * bounceDampen })
-
-	aw.camera.Centre(aw.Pos.Add(aw.Size.Div(2)))
-
+	if zc || aw.Pos != p {
+		aw.camera.Centre(aw.Pos.Add(aw.Size.Div(2)))
+	}
 	return aw.Sprite.Update()
 }