[BUG] Code fence line numbers cause delayed rendering and layout shift

[O-OoOvO]

Code fence line numbers cause delayed rendering and layout shift

Typora 1.13.4 on macOS 15.6.1, Apple Silicon M4.

Typora is paid software, and I am a paid user.

With Preferences → Markdown → Code Fences → Display line numbers for code fences enabled, code blocks do not render line numbers immediately when scrolling.

When a code block enters the visible area, it often appears without line numbers first. After a short delay, the line number gutter suddenly appears on the left side, causing the page to shift, flicker, or repaint. This happens repeatedly when scrolling through documents with multiple code fences.

To reproduce:

1. Enable Display line numbers for code fences.
2. Open a Markdown document with multiple fenced code blocks.
3. Scroll normally.
4. Watch newly visible code blocks.

Expected behavior: code blocks should render with line numbers immediately, without shifting the page after they become visible.

This is not a hardware performance issue. It happens on an M4 Mac.

This bug has existed since 2024 and is still not fixed in Typora 1.13.4. There are already many free Markdown editors. People pay for Typora mainly because they expect a smoother and more convenient experience. Basic rendering bugs like this should not remain unresolved for years in paid software.

If the project lacks maintenance resources, please consider a subscription model instead of leaving long-standing bugs unfixed.