Add support for giving up the selection, forcibly and voluntarily

v2/claim.go

@@ -14,6 +14,8 @@ type Claim struct {
 	window    *xwindow.Window
 	data      Data
 	selection xproto.Atom
+	timestamp xproto.Timestamp
+	active    bool
 }
 
 // NewClaim claims ownership of a specified selection, and allows using data
@@ -50,9 +52,11 @@ func NewClaim (window *xwindow.Window, selection xproto.Atom, data Data, timesta
 	}
 
 	return &Claim {
+		active:    true,
 		window:    window,
 		data:      data,
 		selection: selection,
+		timestamp: timestamp,
 	}, nil
 }
 
@@ -184,3 +188,35 @@ func (claim *Claim) HandlePropertyNotify (
 ) {
 	// TODO
 }
+
+// While the selection claim is active, HandleSelectionClear should be called
+// when the requesting window recieves a SelectionClear event. This must be
+// registered as an event handler manually.
+func (claim *Claim) HandleSelectionClear (
+	connection *xgbutil.XUtil,
+	event xevent.SelectionClearEvent,
+) {
+	// If a client gives up ownership of a selection or if some other client
+	// executes a SetSelectionOwner for it and thus reassigns it forcibly,
+	// the previous owner will receive a SelectionClear event.
+	claim.active = false
+}
+
+// Close voluntarily relinquishes the selection claim. This will inform the X
+// server that the selection is being voluntarily given up, and cause the claim
+// to stop responding to events.
+func (claim *Claim) Close () error {
+	if !claim.active { return nil }
+	claim.active = false
+
+	// To relinquish ownership of a selection voluntarily, a client should
+	// execute a SetSelectionOwner request for that selection atom, with
+	// owner specified as None and the time specified as the timestamp that
+	// was used to acquire the selection. 
+	err := xproto.SetSelectionOwnerChecked (
+		claim.window.X.Conn(),
+		0, claim.selection, claim.timestamp).Check()
+	if err != nil { return err }
+
+	return nil
+}

v2/examples/copy/main.go

@@ -68,6 +68,7 @@ func main () {
 	window.Listen(xproto.EventMaskPropertyChange)
 	xevent.PropertyNotifyFun(claim.HandlePropertyNotify).Connect(X, window.Id)
 	xevent.SelectionRequestFun(claim.HandleSelectionRequest).Connect(X, window.Id)
+	xevent.SelectionClearFun(claim.HandleSelectionClear).Connect(X, window.Id)
 	
 	log.Println("running main event loop")
 	xevent.Main(X)