Module fallback 

Precomputed font fallback chains for resolving font stacks.

A FontFallbackChain is a self-contained snapshot that maps a CSS font stack to the exact fonts that will be used for any character, without requiring further metadata lookups during layout.

Resolution order:

1. The CSS stack in order.
2. The script fallback group whose block contains the character.
3. The configured last resort, without a coverage check.

Structs

CssFallbackGroup

The fonts one entry of the CSS font stack resolved to.

FontFallbackChain

A resolved font fallback chain for one CSS font stack and style.

RankKey

The ordering used wherever font candidates compete. Smaller is better.

ScriptFallbackGroup

Fonts to try for characters inside one Unicode block, best first.

Constants

LAST_RESORT_SOURCE

css_source reported by FontFallbackChain::resolve_char for the configured last resort.

MAX_AUTO_FALLBACKS_PER_SCRIPT

How many coverage-ranked fonts a script fallback group keeps beyond the configured preferences.

MAX_FACES_PER_FAMILY

How many faces of one family a chain keeps (Regular, Bold, Italic, … ranked by closeness to the requested style).

UNICODE_FALLBACK_SOURCE

css_source reported by FontFallbackChain::resolve_char for a font taken from FontFallbackChain::unicode_fallbacks.

Functions

breadth

Total coverage in codepoints.

covers

Returns true if ranges contains cp. ranges must be sorted and disjoint.

overlap_size

Number of codepoints in block that ranges cover, capped at the block’s width.

range_width

Width of a range in codepoints.