NewClaim, NewRequest can return an error

v2/claim.go

@@ -1,6 +1,7 @@
 package xgbsel
 
 import "io"
+import "errors"
 import "github.com/jezek/xgb"
 import "github.com/jezek/xgbutil"
 import "github.com/jezek/xgb/xproto"
@@ -20,7 +21,7 @@ type Claim struct {
 // should be set to that of the event that triggered the claim, such as a Ctrl+C
 // event, or a mouse motion that led to text being selected. If the claim was
 // not triggered by an event, specify xproto.TimeCurrentTime.
-func NewClaim (window *xwindow.Window, selection xproto.Atom, data Data, timestamp xproto.Timestamp) *Claim {
+func NewClaim (window *xwindow.Window, selection xproto.Atom, data Data, timestamp xproto.Timestamp) (*Claim, error) {
 	// Follow:
 	// https://tronche.com/gui/x/icccm/sec-2.html#s-2.1
 	
@@ -39,18 +40,20 @@ func NewClaim (window *xwindow.Window, selection xproto.Atom, data Data, timesta
 	err := xproto.SetSelectionOwnerChecked (
 		window.X.Conn(),
 		window.Id, selection, timestamp).Check()
-	if err != nil { return nil }
+	if err != nil { return nil, err }
 
 	ownerReply, err := xproto.GetSelectionOwner (
 		window.X.Conn(), selection).Reply()
-	if err != nil { return nil }
+	if err != nil { return nil, err }
-	if ownerReply.Owner != window.Id { return nil }
+	if ownerReply.Owner != window.Id {
+		return nil, errors.New("someone else took the selection")
+	}
 
 	return &Claim {
 		window:    window,
 		data:      data,
 		selection: selection,
-	}
+	}, nil
 }
 
 func (claim *Claim) refuseSelectionRequest (request xevent.SelectionRequestEvent) {

v2/examples/copy/main.go

@@ -62,7 +62,7 @@ func main () {
 	// obtain claim on CLIPBOARD
 	log.Println("obtaining claim")
 	clipboard, _ := xprop.Atm(X, "CLIPBOARD")
-	claim := xgbsel.NewClaim(window, clipboard, data, xproto.TimeCurrentTime)
+	claim,     _ := xgbsel.NewClaim(window, clipboard, data, xproto.TimeCurrentTime)
 
 	// listen for events
 	window.Listen(xproto.EventMaskPropertyChange)

v2/examples/paste/main.go

@@ -79,7 +79,7 @@ func main () {
 	log.Println("creating request")
 	clipboard, _ := xprop.Atm(X, "CLIPBOARD")
 	property,  _ := xprop.Atm(X, "DESTINATION")
-	request := xgbsel.NewRequest (
+	request,   _ := xgbsel.NewRequest (
 		requestor { window: window },
 		clipboard,
 		property)

v2/request.go

@@ -48,7 +48,7 @@ type Request struct {
 }
 
 // NewRequest sends a new selection request.
-func NewRequest (requestor Requestor, source, destination xproto.Atom) *Request {
+func NewRequest (requestor Requestor, source, destination xproto.Atom) (*Request, error) {
 	request := &Request {
 		source:      source,
 		destination: destination,
@@ -56,9 +56,9 @@ func NewRequest (requestor Requestor, source, destination xproto.Atom) *Request
 	}
 
 	targets, err := xprop.Atm(requestor.Window().X, "TARGETS")
-	if err != nil { request.die(err); return nil }
+	if err != nil { return nil, err }
 	request.convertSelection(targets, selReqStateAwaitTargets)
-	return request
+	return request, nil
 }
 
 func (request *Request) convertSelection (target xproto.Atom, switchTo selReqState) {