Capturing clicks in label_widget in expander (lablgtk) - gtk

Question

In lablgtk, I have an Expander widget to which I added a button as part of its label, as in this picture:
However, I'm unable to capture clicks to this button, since all of them seem to be captured by the Expander object itself.
I even tried adding an event box between the expander and the button (similarly to what is recommended for clickable GLabels), but that did not help.
Is there a way to ensure the button receives the signal?
Here's a self-contained example to illustrate this: clicking on the button only prints expander activated!, but never button clicked!.
let main () =
(* create expander, a label_widget, and a button *)
let expander = GBin.expander () in
let expander_label = GMisc.label ~text:"expander" () in
let expander_label_widget = GPack.hbox () in
let button = GButton.button ~stock:`OK () in
(* add button to label_widget, and label_widget to expander *)
expander_label_widget#add expander_label#coerce;
expander_label_widget#add button#coerce;
expander#set_label_widget expander_label_widget#coerce;
(* add events for both the button and the expander *)
ignore (button#connect#clicked
~callback:(fun () ->
Format.printf "button clicked!#."));
ignore (expander#connect#activate
~callback:(fun () ->
Format.printf "expander activated!#."));
(* create window and add expander *)
let window = GWindow.window () in
window#add expander#coerce;
ignore (window#connect#destroy
~callback:(fun () -> GMain.Main.quit ()));
(* show result *)
window#show ();
GMain.Main.main ()
let () =
ignore (GtkMain.Main.init ());
main ()

Answer 1

This seems to be a bug in GTK+.
There's a workaround described here but it's in C.
You have to add the following OCaml code to your main function. It worked for me.
GMain.Idle.add (fun () ->
let dummy = GButton.button ~stock:`OK () in
expander#set_label_widget dummy#coerce ;
expander#set_label_widget expander_label_widget#coerce ;
false) ;