Introduce Placer interface (#18)

When implemented, the `Place` method of the `Placer` interface tells `Render` in `El` where to put a Node. This is relevant for helpers that want to be rendered like attributes, inside the parent element.

Fixes the bug where `attr.Classes` was rendered outside the element.

1 files changed, 4 insertions, 0 deletions

diff --git a/attr/attributes.go b/attr/attributes.go
index 56fcd74..415e6f1 100644
--- a/attr/attributes.go
+++ b/attr/attributes.go
@@ -35,6 +35,10 @@ func (c Classes) Render() string {
 	return g.Attr("class", strings.Join(included, " ")).Render()
 }
 
+func (c Classes) Place() g.Placement {
+	return g.Inside
+}
+
 // String satisfies fmt.Stringer.
 func (c Classes) String() string {
 	return c.Render()