Rerun notebook widget eavesdrops on keyboard events while typing in another cell about rerun HOT 7 CLOSED

A quick-fix is to ignore certain events (like "space") when the egui viewport doesn't have focus (ctx.input(|i| i.focused)), but that's assuming focused is correctly set (which I'm not sure it is).

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From slack discussion: we should consider moving the keydown event handler from document to canvas here:

https://github.com/emilk/egui/blob/7bd0a4f7965ebade3c03403d0014bd7e60e67132/crates/eframe/src/web/events.rs#L70-L73

If we do we need to make sure that the canvas gets automatic focus (e.g. on egui.rs and rerui.io/viewer).

In general, any events that can be moved from document to canvas without loss of functionality should be moved in order to better support multiple eframe viewports in the same web view.

Some events, like keyup, should probably stay on document so that we don't miss a key release on e.g. (alt-)tab or similar.

For the events that are installed on document:

• check for focus in any document/window events before doing anything, especially preventDefault/stopPropagation

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In order for the canvas element to be able to accept focus, it also needs to have a tabIndex="0" attribute set. The 0 ensures that the canvas follows the focus order defined by the order in the document source.

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We decided to do a quick-fix for this for now:

Ignore some key presses (space, arrow keys) in Rerun on web if mouse cursor isn't inside the viewer canvas. @jleibs is taking the lead on this.

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Playing around with this the proposed solution still feels quite awkward.

In particular, it becomes evident that keyboard shortcuts are broken in other ways. Events sent while the viewer is in focus still also get processed by the notebook. For example hitting "space" triggers a page-down.

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I realized this is in fact a regression, which is why nobody has complained. This is one of the things we were getting "for free" from the fact that the viewer was previously embedded in an iframe.

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Additional notes:

• emilk/egui#4718 addresses the main issue

There is a second regression which is that jupyter notebook (classic) sometimes responds to Rerun events. In particular, the "a" key when trying to navigate.

I believe this can be traced back to jupyter's keyboard manage itself being somewhat poorly behaved:
https://github.com/jupyter/nbclassic/blob/main/nbclassic/static/notebook/js/keyboardmanager.js#L175-L183

It might be possible for us to detect when we have focus and manually disable the jupyter keybooard manager: https://github.com/jupyter/notebook/blob/ca50f1af5afb525fd95b98b2e61e69db28094467/notebook/static/notebook/js/keyboardmanager.js#L234

This is not an issue in jupyterlab, which appears to follow better practices for event handling.

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