pywebview: Deadlock while closing the window with persistent threads running

When updating the DOM from a separate thread, using calls like webview.evaluate_js() I found it quite useful to have an API call which indicates whether the window is still present / attempting to close.

Problem

If one clicks the close button on a window (rather than quitting it like with Apple + Q), and then a separate thread calls to the webview object, like webview.evaluate_js(), this thread becomes blocked and stuck in that call indefinitely.

What would be helpful is a function like webview.window_exists()

which returns a boolean, which is set within WindowDelegate::windowWillClose_() (and the equivalent location on other platforms). I tested this by adding a global variable to cocoa.py which is set within windowWillClose_, and having webview return the status of this boolean. Certainly not the cleanest way, but it works.

Could we perhaps integrate this in a more OO-friendly fashion. I’m happy to help.

Alternatively, we could provide an API for a callback function, which would be called (in addition to the window closing) when the user hits the “x” or close button on a window. A sort-of cleanup call, to prevent deadlock.

Thoughts? Thanks! Michael