add Deleter and DrawDeleter interfaces

graphics.go

@@ -10,7 +10,7 @@ import (
 
 // Drawer is anything that can be drawn. It's by no means a drawer inside your table.
 //
-// Drawer consists of a single method: Draw. Draw methods takes any number of Transform arguments. It applies these
+// Drawer consists of a single methods: Draw. Draw methods takes any number of Transform arguments. It applies these
 // transforms in the reverse order and finally draws something transformed by these transforms.
 //
 // Example:
@@ -23,6 +23,19 @@ type Drawer interface {
 	Draw(t ...Transform)
 }
 
+// Deleter is anything that can be deleted. All graphics objects that have some associated video memory
+// are deleters. It is necessary to call Delete when you're done with an object, otherwise you're going
+// to have video memory leaks.
+type Deleter interface {
+	Delete()
+}
+
+// DrawDeleter combines Drawer and Deleter interfaces.
+type DrawDeleter interface {
+	Drawer
+	Deleter
+}
+
 // PolygonColor is a polygon shape filled with a single color.
 type PolygonColor struct {
 	parent pixelgl.Doer
@@ -108,3 +121,8 @@ func (pc *PolygonColor) Draw(t ...Transform) {
 
 	pc.va.Draw()
 }
+
+// Delete destroys a polygon shape and releases it's video memory. Do not use this shape after calling Delete.
+func (pc *PolygonColor) Delete() {
+	pc.va.Delete()
+}