WIP ignore IME key clicks

[iezer]

Partial fix for #548. This fixes Korean and Japanese input (using Input Method Editor IME) for most cases.

Editor is still broken when entering text at the beginning of a section. Still working on that. Fixing this will probably involve fixing #589, ie. don't do a full re-render when not needed. This also effects spellcheck and Android input.

Basically the keys Enter, Backspace, Space, Tab, and Arrows are all used to navigate and select within the IME editor so we want mobiledoc to ignore those.

Illustration of the bug:

Pressing Enter

Pressing Backspace

• Pressing backspace seems to duplicate the previous character
  

After fixed

Still broken at start of section

• Notice the "w" goes straight to the document and is not part of the IME input
  

[mixonic]

@iezer are there docs for the IME APIs? I was looking into it and I wasn't sure if FireFox and Chrome have the same APIs here, or if they are standard/non-standard etc.

Looking good.

[iezer]

@mixonic I found some docs here but I'm not sure if they're relevant. https://www.chromium.org/developers/design-documents/extensions/proposed-changes/apis-under-development/input-method-editor

The IME interface is at the OS level so it's the same on all browsers and text-editors, even in the terminal!

I just tested this on Firefox and Safari and it works.

[siygle]

Sorry for asking, any update on this PR? Hope this could merge soon and the IME issue could be solved. :)

[kwmr-zz]

If this bug remains for a long time, no Japanese or Koreans will use it. I WANT SOME- THING TO FIX IT...

[hq5544]

This problem troubles me such a long time.
Hope this PR can be merged soon.
@kevinansfield

[tohutohu]

I strongly hope that this PR will be merged early.
If there is a reason for not being merged, please tell us why.

[xufangda]

Merge it Please!!!

[bin16]

@gpoitch The feature is important for all users who need input method.

[gpoitch]

@bin16 the PR is still incomplete according to the author @iezer. Happy to help push it along if the author or someone else can step up and finish it or confirm it's working as-is. I am no longer contributing to this project.

[xufangda]

@bin16 the PR is still incomplete according to the author @iezer. Happy to help push it along if the author or someone else can step up and finish it or confirm it's working as-is. I am no longer contributing to this project.

Thanks so much for reply. This PR has been proved to be effective by @soulteary. The author @iezer has pointed out that this PR solves problem #548, and this is the biggest problem for every asian user.

The so called incomplete refers to issue #589. We can wait for people proposing a new PR. Please merge this PR first.

[bin16]

I've checked, the PR is a partial fix. It's broken when you insert with IME to an empty section. e.g. typing ceshi with IME, c is caught by editor, and IME take eshi only.

[bin16]

@iezer You can replace key.isIME() with event.isComposing, https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/isComposing

The API is not supported by some browsers(IE), but it would not be worse. https://caniuse.com/#feat=mdn-api_keyboardevent_iscomposing.

[ZeeJab]

Superseded by #738