1. Go to https://w3c.github.io/uievents/tools/key-event-viewer.html
2. Move focus to the <input>
3. Type control + A
4. Type control + option + A
5. Check the "Read only" checkbox
6. Type control + A
7. Type control + option + A
At #3, #4, #6, #7, keypress events won't be fired since keypress events should be fired "f and only if that key normally produces a character value".
#3 does not fire keypress event (as expected)
#4 fires keypress event whose charCode is 1 (invalid)
#6 fires keypress event whose charCode is 1 (invalid)
#7 fires keypress event whose charCode is 1 (invalid)
Firefox will stop dispatching those keypress events.
Chromium also has same bug.
And I found bug 28409 which requests to dispatch keypress events for such non-printable key combinations, but this is clearly invalid for the latest UI Events.
Mass move bugs into the DOM component.
This belongs in UI events.