jupyterlab/jupyterlab

Switching to markdown preview is slow; the scroll position gets lost

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#13,678 opened on Dec 29, 2022

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bughelp wantedpkg:markdownviewertag:Performance

Description

Description

Switching tabs to markdown viewer is slow. It takes ~11 partially presented frames and renderMarkdown gets called twice.

Reproduce

  1. Open JupyterLab README.md with right click: "Open With" → "Markdown Preview"
  2. Open a new launcher
  3. Switch back and forth
  4. See that the markdown tab contents flickers

Screenshot from 2022-12-29 13-51-24

Screenshot from 2022-12-29 13-56-06

For scroll position not being preserved see:

scroll-position-md

Expected behavior

  • We should not need to invalidate the rendered markdown when switching back and forth and definitely we should not call renderMarkdown twice.
  • The scroll position should be preserved.

Context

  • JupyterLab version: 4.0.0a31 and 3.x

Contributor guide

Tech stack
typescript
Domain
frontend
Issue type
performance
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
None
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the markdown preview widget implementation in JupyterLab. Look for the 'renderMarkdown' function calls and understand why it is invoked twice when switching tabs. Examine the widget lifecycle and caching mechanism to avoid re rendering. Also, check how scroll position is stored and restored. Relevant files are likely in the 'packages/markdownviewer' directory. Review the issue comments and any linked PRs for additional context.