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:

• markdown parsing
• cursor positioning
• input focusing
• content copy and pasting
• history undoing/redoing

Linked PRs

Expensify/App#40181 (comment)