Custom Flutter icons that keep their codepoints

Tree shaking, precisely

The provider is emitted the way Flutter's icon subsetting requires: anabstract final class annotated@flutter.staticIconProvider, containing onlyconst IconData values whose codepoint, family, and package are compile-time constants.

That annotation is a promise the analyzer enforces, namely that noIconData in the class is constructed dynamically. Flutter needs that guarantee before it can drop unused glyphs from the font.

What GlyphPact does and does not control. It emits a provider that satisfies the contract. Whether subsetting actually runs is your build's decision: it applies to release builds and is disabled by --no-tree-shake-icons. ConstructingIconData from a variable anywhere else in your app is the usual reason subsetting gets switched off.

Shipping icons from a Dart package

When the font lives in a package rather than the application, pass the package name. The generated IconData constants then carryfontPackage, which is how Flutter resolves the asset from a dependency.

Keep the family entry in the package's ownpubspec.yaml equal to the configured font family, or Flutter will not find the glyphs at runtime.

Icons that genuinely need more than one alpha value

A single icon-font glyph stores one coverage mask, so it cannot hold two different opacities at once. Rather than silently flattening such an icon, GlyphPact can represent it as up to eight ordered solid-alpha outlines, each emitted into an auxiliary font family at the icon's unchanged codepoint.

Opt in per icon, in the config:

The generated Dart adds a layered widget and layer descriptors, and the plain IconData remains available as the fallback you explicitly chose:

The report records every layer's paint order, opacity, family, file, codepoint, and bounds. Seethe runnable layered example.

Check in a config instead of memorising flags

For anything you build more than once, a JSON config beats a shell command. Paths resolve relative to the config file, CLI flags override config values, and jobs: 0 selects up to eight bounded worker processes.

Per-icon entries are also where provenance goes.author, license, sourceUrl, andcopyright flow into the generatedATTRIBUTION.md, which also reports how many emitted icons have no declared provenance at all.

Make CI fail when the committed font goes stale

Generated artifacts drift. Someone edits an SVG and does not regenerate; someone regenerates and does not commit. Without a check, the repository quietly holds a font built from an older pack.

--check rebuilds a candidate set and compares it without rewriting the owned output. It may create the output's parent directory and leaves the sibling coordination file in place. With--json, inspect quality,policy, glyph counts, and typed issues rather than treating every zero exit as equivalent.

Large icon sets

One font holds at most 65,534 usable glyphs, an OpenType indexing limit GlyphPact enforces as a per-build ceiling. In practice the allocation range binds first: the default BMP private use area U+E000 - U+F8FF provides 6,400 lifetime slots, and tombstones consume them too because codepoints are never recycled.

For a larger catalogue, allocate from a supplementary private use area with --start-codepoint 0xF0000, which provides 65,534 slots. Beyond that, split into several independently versioned fonts.

Compile time depends far more on SVG complexity than on file count, so GlyphPact publishes no private-corpus headline number. Thebenchmark guide provides a reproducible local runner for measuring your own pack instead.