Desktop: option-return doesn't work in Mac desktop app

[DanShockley]

I confirm (by marking "x" in the [ ] below: [x]):

• [x] This is not a troubleshooting question.
• [x] This doesn't reproduce on web browsers (such as in Chrome).
• [x] I have read [contributing guidelines]

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https://mattermost.atlassian.net/browse/MM-14177

Summary
While editing a message, the Option-Return keystroke is not supported in the Mac desktop app, although it works properly in the web app.

Environment

• Operating System: macOS 10.12.6 Sierra
• Mattermost Desktop App version: 4.1.2
• Mattermost Server version: 5.3.1

Steps to reproduce

While typing a message, hit Option-Return (aka Option-Enter) on the keyboard.

Expected behavior

A Carriage Return character should be inserted (as it behaves on the web app and most other apps).

Observed behavior

No character is inserted. Nothing happens at all.

Possible fixes

Workaround: use Shift-Return, which works to insert a return character. Option-Return is the most commonly used way to insert a return character in an interface text edit box when a hit on the Return/Enter key (with no modifier) is being used to trigger transmission of the message.

[yuya-oc]

@esethna I think this is a proposal for keystroke on webapp. Would you check this? On other OSes, "Option" would be Alt.

[DanShockley]

This is not a proposal for a keystroke in the webapp.
This is a report that a keystroke that already _does_ work in the webapp, and is a fairly standard Mac keystroke, for some reason does _not_ work in the Mac Desktop app.

[yuya-oc]

Well, probably I could not notice or understand the behavior on my Mac (Chrome and Safari). Would you tell us any apps I can easily see the behavior? Or would you provide a gif animation to show your expected behavior?

[DanShockley]

Ok. In Safari, this issue does NOT happen. The option-return keystroke properly inserts a carriage return. However, I filed this issue in _desktop_, since the Mac _desktop_ app (not Safari!) ignores the option part of option-return. When you do an option-return keystroke in the _desktop_ app, it treats it like a naked Return keypress and transmits your message.
An example of a Mac app where option-return inserts a carriage return instead of sending the message is Slack.app or Skype.app or most other messaging apps.

[amyblais]

Jira ticket for tracking: https://mattermost.atlassian.net/browse/MM-14177.

[hunterlester]

Verified, on macOS, option+return functions as carriage return within web app in Safari.
However, also on macOS, it does not function within web app in Firefox nor in Google Chrome.

If we implement this behavior in the desktop application, we'd also have to duplicate the implementation in the web app, so that macOS users would have a consistent experience.
Better option would be to implement just once in web app for consistent experience in desktop app.

Plus, implementing it in the desktop app, in the webview preload script, wouldn't be a reliable a way to control textarea style and would make further maintenance confusing.

Recommending that this issue is moved to web app repository.