APEX

When using the ‘warn on unsaved changes’ page attribute, APEX pages behave as you would expect. However, the inline help notes this option is not relevant for modal pages.

Note: This does not apply to an end user closing a Modal dialog page.

The following JavaScript offers a fairly self explanatory method of replicating this need, if applied to the JS action of a ‘cancel’ button on a modal form

if (apex.page.isChanged())
  apex.message.confirm('There are unsaved changes. Do you want to continue?'
    ,function(result){
      if(result===true){
        apex.navigation.dialog.cancel(true);
      }
  });
else
  apex.navigation.dialog.cancel(true);  

However, this does not apply when the X button is pressed on the top-right of a modal.

Placing this logic within a shared function for the application is a little tricky. Back in 2017 Jorge Rimblas posted a suggested solution that wasn't quite robust enough to do the job

https://rimblas.com/blog/2017/04/warn-before-closing-apex-modal-dialogs/

but commenter Samuil provided a workaround (search for secondComing)

When the function was placed in a JS file available to the app, it could then be referenced in the Dialog-Attributes field in each relevant modal using

beforeClose: warnOnClose

This was ok in 20.2, but stopped functioning correctly after 22.1.

Instead, it doesn't re-display the confirm() prompt after clicking 'cancel', nor does it close the modal if your press ‘ok’.

Does anyone have a contemporary solution, or any suggestions?

Cheers