Add a method for fetching the main window when it might not exist #874
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Previously, if the main window had been closed, there was no way of trying to access the main window without panicing. There was also no safe way to check if the main window had been closed since that would require fetching the focused window id which might not exist, thus panicing. With these new methods it's possible to easily handle the case when there is no main window or the main window has been closed, using the App::try_main_window method. App::try_window_id is added for completeness, but is not strictly necessary since if there has been at least one window the focused window should be set.
If the main window was closed using the X, the window might not exist in the exit function, causing a panic. Use the new method which returns an Option to handle that case.
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Seem to be a little bit connected to #743 |
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I was trying to work with code similar to the
draw_captur_hi_res.rsexample that rendered to a texture, but my code was crashing when I was closing the nannou window using the Windows "X" button. It turns out that it was panicing in the exit function trying to fetch the main window which seems to have closed before the exit function had a chance to run.I'm not sure if this is the correct solution. Ideally I would change the API of either
App::window_idorApp::main_windowto return anOption. Changingmain_windowwould likely not be great since it would add a lot of boilerplate to the more common case of accessing it outside of the exit function. Changingwindow_idwould require us to check whether thefocused_windowstill existed inwindows. Both of these would be breaking API changes, which is why I choose to implement new methods.Also in my particular case it would be enough to check if
window_countwas 0, though that feels a bit brittle in the general case. Additionally, a real workaround would be to check ifApp::window_idexist inApp::window_ids. That would work since it looks likeApp::focused_windowis set the first time a window is created. In that case I think the docs ofApp::window_idshould be updated to reflect that this is something that is guaranteed.