Merge view - jumping onChange

[natocTo]

Hello,

we are trying to implement merge view into our app and we came across this behaviour.

There is a simple sandbox: https://codesandbox.io/p/sandbox/competent-tom-8zpsy7

Please try to enter severals new lines (for example 50) into second editor (I just keep presed enter for while). When it hits certain point the view "jump" up over active cursor. And anytime you enter another char there (on some latest lines usually), it behave same (jump a little bit up). So it is really hard to write something there.

Did I miss some setting I have to use? Thank you very much for any help.

[jaywcjlove]

@natocTo upgrade v4.23.1

import React, { useState } from 'react';
import CodeMirrorMerge from 'react-codemirror-merge';

const Original = CodeMirrorMerge.Original;
const Modified = CodeMirrorMerge.Modified;
let doc = `one
two
three
four
five`;

export default function App() {
  const [value, setValue] = useState(doc);
  const [valueModified, setValueModified] = useState(doc);
  return (
    <div>
      <CodeMirrorMerge destroyRerender={false}>
        <Original
          onChange={(val) => {
            console.log('~~:1', val);
            setValue(val);
          }}
          value={value}
        />
        <Modified
          onChange={(val) => {
            console.log('~~:2', val);
            setValueModified(val);
          }}
          value={valueModified}
        />
      </CodeMirrorMerge>
      <div style={{ display: 'flex', marginTop: 10 }}>
        <pre style={{ flex: 1 }}>{value} </pre>
        <pre style={{ backgroundColor: '#fff', flex: 1 }}>{valueModified} </pre>
      </div>
    </div>
  );
}

[cjayyy]

@jaywcjlove Thank you for the update!
The destroyRerender={false} seems to solve the glitch for us. But with that the custom theme and extensions no longer work. Do you know why by any chance?

[jaywcjlove]

@cjayyy After the MergeView is initialized, it doesn't update the extensions. I guess it might be that your extensions are loaded asynchronously.

react-codemirror/merge/src/Internal.tsx

Lines 67 to 90 in e79b1f3

	useEffect(() => {
	if (!view.current && editor.current && originalExtension && modifiedExtension) {
	view.current = new MergeView({
	a: {
	...original,
	extensions: [
	...(originalExtension?.extension || []),
	...getDefaultExtensions({ ...originalExtension?.option, theme }),
	originalUpdateListener,
	],
	},
	b: {
	...modified,
	extensions: [
	...(modifiedExtension?.extension || []),
	...getDefaultExtensions({ ...modifiedExtension?.option, theme }),
	modifiedUpdateListener,
	],
	},
	parent: editor.current,
	...opts,
	});
	}
	}, [view, editor, originalExtension, modifiedExtension]);

If your extensions are asynchronous, add them to the editor.

react-codemirror/www/src/pages/examples/Example681.tsx

Lines 49 to 53 in e26ca15

	const handle1 = () => {
	$ref.current?.view?.a.dispatch({
	effects: StateEffect.appendConfig.of([log2UpdatePlugin]),
	});
	};

Implementing extensions updates inside the editor causes errors, and I haven't found a solution for this. It may require support from the CodeMirror team, and you can seek answers from their community.

react-codemirror/merge/src/Internal.tsx

Lines 99 to 102 in e26ca15

	// effects: StateEffect.reconfigure.of([
	// ...(originalExtension?.extension || []),
	// ...getDefaultExtensions({ ...originalExtension?.option, theme }),
	// ])

[cjayyy]

Not using any async extensions. Even if I use only minimal setup like below, destroyRerender={false} completely disables the functionality of those two extensions (both editors are editable). When setting destroyRerender={true}, extensions work.

<CodeMirrorMerge destroyRerender={false}>
   <CodeMirrorMerge.Original
      value="first"
      extensions={[EditorView.editable.of(false), EditorState.readOnly.of(true)]}
   />
   <CodeMirrorMerge.Modified value="second" />
</CodeMirrorMerge>

[jaywcjlove]

@cjayyy My example test didn't have any issues -> https://uiwjs.github.io/react-codemirror/#/examples/681

react-codemirror/www/src/pages/examples/Example681.tsx

Lines 59 to 66 in e26ca15

	<CodeMirrorMerge ref={$ref} destroyRerender={false}>
	<Original
	value={value}
	extensions={[log1UpdatePlugin]}
	onChange={(val) => {
	setValue(val);
	}}
	/>

[cjayyy]

Oh I overlooked you published version 4.23.2 - with that it works! (4.23.1. didn't work for me).
Thank you very much. Will test it more thoroughly tomorrow. 🤞

[cjayyy]

Thank you. It looks like the original issue with lines jumping is fixed now.

We are still struggling with another (probably) unrelated issue though;
When changing the doc value fast enough the change handlers (our outside onChange handler` and your internal change dispatching) get mixed up and cycled in and infinite loop causing last change undoing and redoing forever leaving the editor stuck unusable.
My guesses:

• It is caused by this: CodeMirrorMerge gets unfocused on value change #566 (comment)
• It could get fixed by this: Using this as a "controlled" component? #273 (comment) - but I don't understand how to implement it.

Could please point me into the right direction? 🙏

[natocTo]

@jaywcjlove it looks like after update to v4.23.1 (and newer) the onChange is actually not called at all.

Check this sandbox - https://codesandbox.io/p/sandbox/gracious-chandrasekhar-zqmsy9?file=%2Fsrc%2FApp.js it should show alert when updating a value. But it is not called.

[jaywcjlove]

@natocTo I suggest using the approach in the example below to handle the onChange event.

<Modified
  onChange={(val) => {
    console.log('~~:2', val);
    setValueModified(val);
  }}
  value={valueModified}
/>