ui: let OpsReader keep track of references

Instead of exposing the entire reference slice, return the relevant
references from Next.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/key/key.go

@@ -3,8 +3,6 @@
 package key
 
 import (
-	"encoding/binary"
-
 	"gioui.org/ui"
 	"gioui.org/ui/internal/ops"
 )
@@ -73,30 +71,26 @@ const (
 func (h OpHandler) Add(o *ui.Ops) {
 	data := make([]byte, ops.TypeKeyHandlerLen)
 	data[0] = byte(ops.TypeKeyHandler)
-	bo := binary.LittleEndian
 	if h.Focus {
 		data[1] = 1
 	}
-	bo.PutUint32(data[2:], uint32(o.Ref(h.Key)))
-	o.Write(data)
+	o.Write(data, []interface{}{h.Key})
 }
 
 func (h *OpHandler) Decode(d []byte, refs []interface{}) {
-	bo := binary.LittleEndian
 	if ops.OpType(d[0]) != ops.TypeKeyHandler {
 		panic("invalid op")
 	}
-	key := int(bo.Uint32(d[2:]))
 	*h = OpHandler{
 		Focus: d[1] != 0,
-		Key:   refs[key].(Key),
+		Key:   refs[0].(Key),
 	}
 }
 
 func (h OpHideInput) Add(o *ui.Ops) {
 	data := make([]byte, ops.TypeHideInputLen)
 	data[0] = byte(ops.TypeHideInput)
-	o.Write(data)
+	o.Write(data, nil)
 }
 
 func (Edit) ImplementsEvent()  {}