config

DOM-free editor layout values and canonical font identities.

Nothing in this package measures anything — measurement needs a browser and lives in internal/viewer/browser/config. What lives here is the identity of a font configuration: the value that decides whether two configurations may share a measurement cache entry, and the normalization rules that turn raw option input into that identity.

flowchart LR
  O["raw options<br>family, weight, size,<br>line_height, letter_spacing…"]
  O -->|"BareFontInfo::create<br>(normalizes)"| B["BareFontInfo<br>8-axis identity"]
  B -->|get_id| K["cache key string"]
  B -->|"FontInfo::estimated<br>(untrusted)"| E["FontInfo"]
  B -->|"browser measurement<br>internal/viewer/browser/config"| M["FontInfo (trusted)"]
  E --> R["render / layout"]
  M --> R

#Font contract

BareFontInfo is the eight-axis measurement/cache identity: pixel ratio, family, weight, size, feature settings, variation settings, integer line height, and letter spacing. get_id joins those axes in that order.

///|
test "get_id joins the eight axes in declaration order" {
  let bare = @config.BareFontInfo::create(
    font_family="Menlo",
    font_weight="normal",
    font_size=12.0,
    font_feature_settings=@config.editor_font_ligatures_off,
    font_variation_settings=@config.font_variation_off,
    line_height=18.0,
    letter_spacing=0.0,
    pixel_ratio=2.0,
  )
  debug_inspect(
    bare.get_id(),
    content=(
      #|"2-Menlo-normal-12-\"liga\" off, \"calt\" off-normal-18-0"
    ),
  )
}

#Line-height normalization

BareFontInfo::create follows Monaco's line-height normalization: 0 uses the platform golden ratio, nonzero values below 8 are em multipliers, the result is rounded and floored at 8. The readonly viewer has no editor-zoom option, so Monaco's zoom multiplier is fixed at 1.

flowchart TB
  I["raw line_height"] --> Z{"== 0 ?"}
  Z -->|yes| G["golden_line_height_ratio × font_size"]
  Z -->|no| S{"< 8 ?"}
  S -->|yes| EM["line_height × font_size<br>(treated as em)"]
  S -->|no| PX["line_height<br>(treated as px)"]
  G --> R["round"]
  EM --> R
  PX --> R
  R --> F["max(result, minimum_line_height = 8)"]

The golden ratio is platform-dependent, so the example asserts the rule rather than a fixed number.

///|
fn line_height_for(raw : Double, size : Double) -> Int32 {
  @config.BareFontInfo::create(
    font_family="Menlo",
    font_weight="normal",
    font_size=size,
    font_feature_settings=@config.editor_font_ligatures_off,
    font_variation_settings=@config.font_variation_off,
    line_height=raw,
    letter_spacing=0.0,
    pixel_ratio=1.0,
  ).line_height
}

///|
test "zero means the platform golden ratio times the font size" {
  let ratio = if @base_common.is_macintosh { 1.5 } else { 1.35 }
  let expected = (ratio * 14.0).round().to_int()
  debug_inspect(
    (line_height_for(0.0, 14.0) == expected, expected >= 8),
    content=(
      #|(true, true)
    ),
  )
}

///|
test "below 8 is an em multiplier, 8 and above is a pixel value" {
  debug_inspect(
    (
      // em multipliers
      line_height_for(1.5, 20.0),
      line_height_for(2.0, 20.0),
      // pixel values
      line_height_for(24.0, 20.0),
      line_height_for(24.4, 20.0),
      // rounded, then floored at the minimum
      line_height_for(0.1, 20.0),
      8,
    ),
    content=(
      #|(30, 40, 24, 24, 8, 8)
    ),
  )
}

#Font variation translation

Variation setting translate preserves normal/bold as ordinary weight with variation normal. Other weights use JavaScript parseInt(_, 10) decimal-prefix semantics, emit 'wght' N, and normalize the retained weight to normal.

The parseInt fidelity is literal, including its failure mode: a CSS keyword weight such as lighter has no decimal prefix, so the axis is emitted as 'wght' NaN. That is the upstream behavior rather than a local defect, and it is why callers pass numeric weights when they enable translate.

///|
fn translated(weight : String) -> (String, String) {
  let bare = @config.BareFontInfo::create(
    font_family="Menlo",
    font_weight=weight,
    font_size=12.0,
    font_feature_settings=@config.editor_font_ligatures_off,
    font_variation_settings="translate",
    line_height=0.0,
    letter_spacing=0.0,
    pixel_ratio=1.0,
  )
  (bare.font_weight, bare.font_variation_settings)
}

///|
test "translate emits a wght axis for numeric weights only" {
  debug_inspect(
    (
      translated("normal"),
      translated("bold"),
      translated("600"),
      // parseInt decimal-prefix semantics: trailing junk is ignored
      translated("350abc"),
      // no leading digits: parseInt yields NaN, and it is emitted verbatim
      translated("lighter"),
    ),
    content=(
      #|(
      #|  ("normal", "normal"),
      #|  ("bold", "normal"),
      #|  ("normal", "'wght' 600"),
      #|  ("normal", "'wght' 350"),
      #|  ("normal", "'wght' NaN"),
      #|)
    ),
  )
}

#FontInfo

MoonBit has no class inheritance, so FontInfo is the flattened BareFontInfo fields plus the measured trust, monospace, half/full-width, arrow, space, middot, word-separator-middot, and maximum-digit facts.

FontInfo::equals is Monaco's render/configuration identity: it deliberately ignores pixel_ratio, is_trusted, and is_monospace. Structural == still compares every MoonBit field; callers needing Monaco identity must use equals. Using == where equals was meant causes spurious re-layout when a window moves between displays.

///|
test "equals ignores pixel_ratio and trust, while == does not" {
  let bare = @config.BareFontInfo::create(
    font_family="Menlo",
    font_weight="normal",
    font_size=12.0,
    font_feature_settings=@config.editor_font_ligatures_off,
    font_variation_settings=@config.font_variation_off,
    line_height=0.0,
    letter_spacing=0.0,
    pixel_ratio=1.0,
  )
  let one = @config.FontInfo::estimated(bare)
  let retina = {
    ..one,
    pixel_ratio: 2.0,
    is_trusted: true,
    is_monospace: true,
  }
  debug_inspect(
    (one.equals(retina), one == retina),
    content=(
      #|(true, false)
    ),
  )
}

FontInfo::estimated and FontInfo::default are untrusted headless values used before DOM measurement. Font-info versioning, serialization, and restore are absent because the viewer has no persistence channel.

///|
test "headless font info is explicitly untrusted" {
  let fallback = @config.FontInfo::default()
  debug_inspect(
    (
      fallback.is_trusted,
      @config.FontInfo::estimated(fallback.bare()).is_trusted,
      fallback.bare().font_size == fallback.font_size,
    ),
    content=(
      #|(false, false, true)
    ),
  )
}

#Defaults

editor_font_defaults selects the exact Menlo stack and 12px size on macOS, the Consolas stack and 14px size on Windows, and the Droid Sans Mono stack and 14px size elsewhere. Default weight is normal; raw line height and letter spacing are zero.

The three stacks are individually addressable, so a caller can name one without depending on which platform the test happens to run on.

///|
test "the three platform stacks are named constants" {
  debug_inspect(
    (
      @config.default_mac_font_family, @config.default_windows_font_family, @config.default_linux_font_family,
    ),
    content=(
      #|(
      #|  "Menlo, Monaco, 'Courier New', monospace",
      #|  "Consolas, 'Courier New', monospace",
      #|  "'Droid Sans Mono', monospace",
      #|)
    ),
  )
}

///|
test "the platform-independent parts of the defaults" {
  let defaults = @config.editor_font_defaults
  debug_inspect(
    (
      defaults.font_weight,
      defaults.line_height,
      defaults.letter_spacing,
      // the size is 12 on macOS and 14 elsewhere
      defaults.font_size == 12.0 || defaults.font_size == 14.0,
    ),
    content=(
      #|("normal", 0, 0, true)
    ),
  )
}

#Layout

EditorLayoutInfo is the resolved horizontal band structure — glyph margin, line numbers, decorations, content — plus the overall size and scrollbar extents. It is a plain value: this package computes no layout, it only gives the layout result one shared shape.

///|
test "EditorLayoutInfo bands are left offsets plus widths" {
  let layout : @config.EditorLayoutInfo = {
    width: 800.0,
    height: 600.0,
    glyph_margin_left: 0.0,
    glyph_margin_width: 0.0,
    line_numbers_left: 0.0,
    line_numbers_width: 40.0,
    decorations_left: 40.0,
    decorations_width: 10.0,
    content_left: 50.0,
    content_width: 736.0,
    horizontal_scrollbar_height: 12.0,
    vertical_scrollbar_width: 14.0,
  }
  debug_inspect(
    (
      layout.content_left == layout.decorations_left + layout.decorations_width,
      layout.content_left +
      layout.content_width +
      layout.vertical_scrollbar_width ==
      layout.width,
    ),
    content=(
      #|(true, true)
    ),
  )
}

#Boundaries and checks

This package is multi-target and depends only on base/common. See pkg.generated.mbti.

moon test --target js viewer/common/config
moon test --target native viewer/common/config

#viewer/common/config

#Font contract

#Line-height normalization

#Font variation translation

#FontInfo

#Defaults

#Layout

#Boundaries and checks

#BareFontInfo

#BareFontInfo::create

#BareFontInfo::equal

#BareFontInfo::get_id

#BareFontInfo::get_massaged_font_family

#BareFontInfo::not_equal

#BareFontInfo::to_repr

#EditorFontDefaults

#EditorFontDefaults::equal

#EditorFontDefaults::not_equal

#EditorFontDefaults::to_repr

#EditorLayoutInfo

#EditorLayoutInfo::equal

#EditorLayoutInfo::not_equal

#EditorLayoutInfo::to_repr

#FontInfo

#FontInfo::bare

#FontInfo::default

#FontInfo::equal

#FontInfo::equals

#FontInfo::estimated

#FontInfo::get_id

#FontInfo::not_equal

#FontInfo::to_repr

#default_linux_font_family

#default_mac_font_family

#default_windows_font_family

#editor_font_defaults

#editor_font_ligatures_off

#font_variation_off

Source Files

BareFontInfo

BareFontInfo::create

BareFontInfo::equal

BareFontInfo::get_id

BareFontInfo::get_massaged_font_family

BareFontInfo::not_equal

BareFontInfo::to_repr

EditorFontDefaults

EditorFontDefaults::equal

EditorFontDefaults::not_equal

EditorFontDefaults::to_repr

EditorLayoutInfo

EditorLayoutInfo::equal

EditorLayoutInfo::not_equal

EditorLayoutInfo::to_repr

FontInfo

FontInfo::bare

FontInfo::default

FontInfo::equal

FontInfo::equals

FontInfo::estimated

FontInfo::get_id

FontInfo::not_equal

FontInfo::to_repr

default_linux_font_family

default_mac_font_family

default_windows_font_family

editor_font_defaults

editor_font_ligatures_off

font_variation_off