some refinement

common/elements/v1/core/config.go

@@ -0,0 +1,17 @@
+package core
+
+import "git.vezzani.net/ben/games/common/elements/v1"
+
+type OptFunc func(*Element)
+
+func Children(children ...elements.Element) OptFunc {
+	return func(c *Element) {
+		c.children = children
+	}
+}
+
+func Name(name string) OptFunc {
+	return func(s *Element) {
+		s.name = name
+	}
+}

common/elements/v1/core/core.go

@@ -0,0 +1,32 @@
+package core
+
+import (
+	"git.vezzani.net/ben/games/common/elements/v1"
+	"git.vezzani.net/ben/games/common/elements/v1/mouse"
+	"git.vezzani.net/ben/games/common/geo"
+)
+
+type Element struct {
+	mouse.NopHandler
+
+	anchor   geo.Point
+	children []elements.Element
+
+	name string // For debugging
+}
+
+func (c *Element) Anchor() geo.Point {
+	return c.anchor
+}
+
+func (c *Element) SetAnchor(a geo.Point) {
+	d := c.Anchor().Delta(a)
+	for _, ch := range c.Children() {
+		ch.SetAnchor(ch.Anchor().Add(d))
+	}
+	c.anchor = a
+}
+
+func (c *Element) Children() []elements.Element {
+	return c.children
+}