Description

Detailed Changes

• Makes TextLayoutManager a text storage delegate.
• Updates TextLayoutManager to use the text storage methods to update internal state.
• Remove TextLayoutManager's layout transaction capabilities.
• Updates replaceCharacters to reflect the new layout manager requirements.
• Moves layout back into a CATransaction, now that method ordering is slightly different, macOS might call layout on the text view while we're laying out text. Doing that in a transaction ensures that doesn't happen and layout is atomic.

Tests

• Adds tests to the layout manager to ensure modifications are kept valid.
• Adds tests for rects(in:) to ensure it doesn't invalidate layout information.
• Adds a test ensuring editing text contents in a text view delegate callback doesn't break layout.

Discussion

This change untangles the text layout updating from text view code. Right now the hierarchy looks like this:

(Update occurs)
TextView -> Text Layout Update
         -> Text Storage Update

This isn't great, because it means anything that modifies the text outside of the text view must remember to update layout, selection, send notifications, and do it all in the right order. I'd like to move it to this hierarchy:

(Update occurs)
TextView -> Text Storage Update -> Text Layout Update

This way any component can modify the text storage, and that will be reflected in the layout manager. There's a myriad of small bugs in our editor right now that are effected by this.

One key result of this change is the ability to correctly modify text in textView delegate callbacks. Right now, if the text is updated in a callback, it can lead to a recursive layout call to the text layout manager. This leads to bad internal state, and bugs where entire sections of text disappear entirely.

This also comes with a performance boost. Since NSTextStorage automatically coagulates text changes, we'll perform less layout passes for each edit, and components can make use of the text storage's transaction capabilities to only cause layout after all edits have been applied in a transaction.

Related Issues

• Could be related to 🐞 Crash when deleting text CodeEditSourceEditor#196

Checklist

• Add Tests
• I read and understood the contributing guide as well as the code of conduct
• The issues this PR addresses are related to each other
• My changes generate no new warnings
• My code builds and runs on my machine
• My changes are all related to the related issue above
• I documented my code

Screenshots