Live Markdown for web refactor

[Skalakid]

Details

This PR refactors the web implementation of the Live Markdown library. The main goals of it are:

• enhancing algorithms and logic behind Markdown Input, to make the project more flexible and enable the possibility of adding new more complex features like inline images or code blocks
• changing and organizing Markdown input HTML structure, to meet the industry standards, fixing problems with cursor positioning and problems with scrolling into view
• improving code quality, to make the codebase more understandable and boost the developer experience

During this refactor phase we:

• changed web live markdown HTML structure so now:

  • every line is represented as paragraph element <p> - it makes structure much clear and organized, and enables us to apply custom logic to specific lines
  • every text is wrapped with <span data-type="text"> tag - by wrapping text with HTML element we enable many useful functions that aren't available in normal text node, for example: scrollIntoView()
  • instead of \n characters inside the input's HTML structure we use <br> tags - br tags give use much more flexibility and fix problem with cursor navigation when using arrow keys when moving between markdown components
  • every <br> tag is wrapped with <span data-type="br"> tag - it fixes many problems connected to cursor positioning

  Thanks to the new structure we enabled the usage of many styles that were generating a lot of bugs in the past, like display: block. Also were able to remove all workarounds connected to cursor positioning.

• added HTML tree node structure, that represents current HTML dom and stores many important information about every element inside the input. Thanks to this tree structure we can easily interact with the markdown elements and we were able to completely refactor and improve the performance of cursor positioning algorithms

• replaced all text value representation functions like process value or normalizeValue with one textContent variable that always contains properly formatted text value without any additional newlines from contentEditable

• split long files of code into smaller ones, and sort functions into utils

• prepared the code for new, more complex features like inline images

This refactor was made as a part of inline image feature. After discovering some structure and logic limitations when creating inline image POC we decided to improve Live Markdown for web.

This refactor will fix or unblock following issues:

• inline images feature
• code block background improvement
• problems with cursor position while navigating by arrow keys between markdowns
• problems with HTML injections on paste
• enable adding styles per text line

Related Issues

GH_LINK

Manual Tests

Since it's a big change it would be great to test it in all cases connected to:

1. Adding text / Markdown
2. Selection
3. Cursor positioning
4. Number of lines
5. Scroll into view
6. Placeholder
7. History - undo/redo
8. Pasting
9. Copy / Cut
10. Composition events
    • Web:
      • Diacritics
      • Text replacement on mac
    • mWeb:
      • Diacritics
      • Autocorrection
11. Spellcheck
    • Web:
      • Chrome
      • Safari
      • Firefox (not working)
    • mWeb:
      • iOS Safari
      • Android Chrome

Linked PRs

Expensify/App#40181 (comment)

[JKobrynski]

I've been trying to fix this Android web issue (you can see some of my takeaways in the comments). It led me to parseText method in parserUtils.ts, more specifically these lines:

 if (!rootSpan || rootSpan.innerHTML !== dom.innerHTML) {
      targetElement.innerHTML = '';
      targetElement.innerText = '';
      target.appendChild(dom);

      if (BrowserUtils.isChromium) {
        moveCursor(isFocused, alwaysMoveCursorToTheEnd, cursorPosition, target);
      }
 }

I also contacted @BartoszGrajdek (shout out to him) to discuss it and he suggested to give this PR a try, as it refactors the web implementation. Here is what I discovered on both web and Android web:

(I had to remove TEST_CONST.EXAMPLE_CONTENT as the bug that I'm trying to fix only occurs for an empty input)

Case 1

- const [value, setValue] = React.useState(TEST_CONST.EXAMPLE_CONTENT);
+ const [value, setValue] = React.useState();

Voice recognition works, markdown doesn't work

Case 2

- const [value, setValue] = React.useState(TEST_CONST.EXAMPLE_CONTENT);
+ const [value, setValue] = React.useState('');

Voice recognition doesn't work, markdown works

To test the voice recognition, I started from an empty input and dictated a sentence, to test markdown I simply typed * bold * or something similar.

[BartoszGrajdek]

LGTM! ✅

[drminh2807]

Hi @Skalakid
Can you explain why you check for <div><br></div> instead of just <br> ?
Is there any document on how browsers add <br> when input is empty
Thanks for your help

[Skalakid]

Hello @drminh2807, it is because contenteditable tries to put everything into <div> elements by default. Especially when you have an empty input, the HTML content looks as follows:

<div><br /></div>

Because of this, when pasting text, a newline appears at the end of the new text. So we can remove it since it's kind of an "invisible" newline. There are more such situations, that's why we have inputUtils that parse contenteditable text content

[Skalakid]

Is there any document on how browsers add
when input is empty

I haven't found one, every browser has different behaviour, so even if there is any article, it may describe only one of them

[drminh2807]

Thanks for your information
After debugging, I found that the browser no longer adds <div> wrapper around <br>, just <br> so this line of code no longer runs
Is there any documentation or evidence that this code used to run and now doesn't?
Is it because of browser changes?

[Skalakid]

It still wraps line content with <div>, but after every newline, and that when this code is executed :D

Screen.Recording.2025-07-14.at.08.41.54.mov

[Skalakid]

As far as I know, we don't have any documentation about parsing behavior. If you see that this condition is generating some issue, please submit a PR with repro steps, and we will review it ;)

[drminh2807]

Thanks for your super help
But I can't replicate like you
I just ran latest main 0.1.292, but the log is quite different and no removing the last br fired

Screen.Recording.2025-07-15.at.08.04.47.mov