Skip to content

docs: document breakableFitAdvances cache invariant #139

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
shaun0927 wants to merge 1 commit into
base: main
Choose a base branch
from
Open

docs: document breakableFitAdvances cache invariant #139

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions src/measurement.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -200,6 +200,11 @@ export function getSegmentBreakableFitAdvances(
emojiCorrection: number,
mode: BreakableFitMode,
): number[] | null {
// The cached result is mode-agnostic: the current call sites guarantee that
// a given segment text always arrives with the same mode, because mode is
// determined by isNumericRunSegment(text) (text-deterministic) and the
// session-invariant engine profile. If a future caller breaks this
// invariant, the cache will silently return the wrong advances.
if (metrics.breakableFitAdvances !== undefined) return metrics.breakableFitAdvances

const graphemeSegmenter = getSharedGraphemeSegmenter()
Expand Down