[belugaming]

#21 fixed the refresh-rate flicker on macOS 27 ProMotion panels. To hold 120 Hz, or whatever the screen supports, every frame also has to finish in about 8 ms on the main thread. That has to hold on slower Macs too, not only on an M5 Max. This PR removes the biggest per-frame costs that are left on the scrolling pages.

Formulas: typeset once, drawn as an image

MarkdownView drew every formula as a ViewThatFits holding two live MTMathUILabels (AppKit views), one of them inside a horizontal scroll view.

• Each label parsed its LaTeX again on every update.
• Each label ran SwiftMath's whole typesetter on every size query, with no cache.
• So a paragraph of notes with a few formulas created a dozen AppKit views and typeset each formula several times whenever it scrolled into view.
• Formulas only came back in 0.16.5, so this cost is new for most users.

MarkdownView 3.0.0 is now a copy in Packages/MarkdownView (MIT, license kept), with only the formula drawing changed:

• SwiftMathImageCache typesets a formula once per look (LaTeX, size, inline or display, light or dark). It uses SwiftMath's own MTMathImage.
• The view draws that image. It is vector-backed, so it stays sharp at any scale.
• A formula wider than its line is scaled to fit instead of scrolling sideways.
• LaTeX the typesetter rejects shows as its source, where it used to show nothing.

Packages/MarkdownView/PATCHES.md lists the three changed files and how to update the copy. MarkdownRendering now depends on the copy by path, still with the LaTeX trait, so the CI check for ENABLE_MATH_RENDERING and SwiftMath's resources still applies.

Refresh-rate request follows the screen

The scroll-time request from #21 now asks for the window's screen maximum, taken from NSScreen.maximumFramesPerSecond, instead of a fixed 120 Hz. A 144 Hz monitor gets 144 Hz. A 60 Hz screen has no other rate to settle on, so nothing is asked of it. The scrollFrameRate setting still overrides this, capped at what the screen can show.

Transcript and session list

• The transcript is grouped into sentences once per change, not on every redraw. A redraw happens on every change to the session's view model, including each streamed token.
• A transcript row draws its rounded background only while it is highlighted or under the pointer. Before, a clear shape sat behind every row.
• Date formatters are made once per template and language. Before, the session list made one per row and section header as it scrolled.
• The session list groups sessions by day once per redraw. Before, it regrouped them once per day header.

Tests

• FormulaRenderingTests renders $$x^{2}$$ through RichMarkdownView with ImageRenderer and checks the pixels:

  • something is drawn;
  • the exponent sits clearly above the x, which raw $$x^{2}$$ source or an upside-down image would fail.

  The old AppKit label rendered nothing off screen.

• ScrollFrameRateTests covers the screen-dependent range: 120 Hz ProMotion, a 144 Hz monitor, 60 Hz left alone, the setting capped at the screen, and every range well formed.

Not measured on hardware. CI builds and tests on macOS 15 and 27, but has no display to time scrolling against. Whether the scrolling pages now hold the full rate has to be seen on a real Mac.

Version 0.16.8 (build 26).

🤖 Generated with Claude Code

https://claude.ai/code/session_01UP49VoRGBw2wv1CEAroky7

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Generated by Claude Code