VIM - Strange behavior in VIM mode with Controlled Usage

[edmondxiexie]

The VIM mode has strange behavior when working with states. For example, when I press either 'o' or 'i' to enter insert mode, then press Backspace. It doesn't seem to allow me to delete previous characters before the insert position, which seems weird. And also, the cursor in insert mode will change from the line shape to the block shape after one insertion operation. Is it related to the rerendering when state changing? Because it does not happen in UnControlled Usage.

I use the OnClick function to change the state and use states for changing the value in the editor.

Preview:

• I enter the edit mode and move cursor to the end of the line.
  

• Then I press Backspace and the cursor change its shape and I cannot delete any more.
  

[scniro]

Interesting, thanks for opening this up, I'll give this a look later today. There is a bit of logic going on for controlled mode to retain/set the cursor in certain cases. I hope VIM isn't going to be a one-off to work around this. I'll keep you posted!

[scniro]

@edmondxiexie Sorry for the delayed response. Okay yep I can definitely reproduce this. Can you use the uncontrolled variant for now? I'm unsure how much work this could entail. I haven't used this mode before nor am I that much of a VIM power user, so when looking for somewhere to get started I came across this on this note over on codemirror

The CodeMirror vim bindings do not have an active maintainer. That means that if you report bugs in it, they are likely to go unanswered. It also means that if you want to help, you are very welcome to look at the open issues and see which ones you can solve.

This has me a little hesitant to dive in as it could lead to an unraveling of who knows what. Either way, I'll start to look and keep you posted.

[scniro]

@edmondxiexie okay so I dug into this a bit and think I may know whats going on here. Basically, for the controlled component there is also a dummy DOMless codemirror instance that mirrors and tracks changes, to which is later applied to the main instance upon state management (new props). However, when using VIM mode (and likely others), there is a notion of a key map that alters the behavior of the editor e.g. for insert => press "i"

The issue is, I don't believe I can emulate this key event to the mirror (dummy), so when I go ahead and extract the mirrored value, it's now incorrect because the keymap altered what would have been applied to the main instance, and is something different entirely. So what I've been digging for is a way to trigger a keystroke change programatically to the dummy, but I have been having trouble to find such a way.

There is a keyHandled callback which is an absolutely perfect hook to apply the emulated event to the dummy, however I'm struggling to find a way to do so through the APIs. I thought maybe I could even grab the native <textarea> and manually dispatchEvent to it - but I can't get _the dummys instance to fire keyHandled.

I might need help with this one, but I'll keep at it when I have time.

[xralphack]

same issue on both Controlled and UnControlled

[scniro]

@xralphack odd, this shouldn't be an issue for uncontrolled

[xralphack]

@scniro you are right, just ignore my comment

[scniro]

@xralphack Cool - no worries. Yea I haven't been able to make a lot of forward progress on this one. It's pretty gnarly on the inside of whats going on as you can see in my investigation above, so hopefully the uncontrolled component is a decent workaround for you, for now.

[xralphack]

@scniro I figured out the problem

I want to wrap the codemirror2 component

// wrapper component

<MarkdownEditor
  markdown={originMarkdown}
  onMarkdownChanged={markdown => this.setState({ markdown })}/>

// codemirror2 component

class MarkdownEditor extends Component {
  ...
  render() {
    return (
      <CodeMirror
         ref="cm"
         value={this.state.initialMarkdown}
         options={{
           keyMap: 'vim'
         }}
         onChange={(editor, data, value) => {
           this.props.onMarkdownChanged();
         }}
    );
  }

use uncontrolled version not work, I think this is due to the parent component rerender
so after add the following, it works fine.

shouldComponentUpdate(nextProps, nextState){
  return false;
}

anyway, thanks for your effort.

[scniro]

@xralphack shouldComponentUpdate for UnControlled? Interesting, very. I use this lifecycle hook when responding to new props via the uncontrolled component for resetting values, setting a new theme, etc. Do you think "freezing" the component once it's mounted would solve this via freeze={true}, or something? (Unsure on naming) That prop would essentially do exactly as you shared and prevent any updates. I think that could be valuable if a user actually wanted that behavior, as your use case is showing. Please let me know if that makes sense?

[xralphack]

@scniro I think using freeze makes sense, but I am not sure using boolean prop is ok for all conditions

[scniro]

@xralphack why would it not be okay? shouldComponentUpdate () => false essentially never updates. I am going to add a detachOnMount boolean that does this

[xralphack]

maybe someone want to toggle this boolean on specific condition ( I'm not sure)

[scniro]

@xralphack gotcha. So I'm thinking then of a detach={variable} that can be bound, so whenever it's truthy the component will not update at all, but when false will behave as normal. Does that sound better?