1.60.4 Get methods

font <-points: -> num

Specified font<-points, or font<-height when font<-points is @default.

font <-ascent: -> num

font <-descent: -> num

Pixels above / below the baseline.

font <-height: -> num

Cap height of the tallest character; equal to font<-ascent.

font <-ex: -> num

Pixel height of the letter x.

font <-avg_char_width: -> num

Average glyph advance in pixels.

font <-size: -> size

size(width('x'), <-height) — convenient when laying out by cell size.

font <-width: [char_array] -> num

Pixel width of the argument string when rendered in this font (defaults to "x").

Counts ink extents, so a glyph with a wide left side-bearing contributes its visual width. font<-advance reports the cursor movement instead (the sum of glyph advances), which is what layout code usually wants.

See also

- font<-advance
- graphical->clip

font <-advance: char_array -> num

Cursor advancement when the string is rendered: the sum of the glyph advances along the baseline. Use this rather than font<-width to position the next glyph after a string.

font <-rescale: num -> font

Return a font with the same family, style and weight but font<-points multiplied by the argument:

?- get(font(sans, roman, 10), rescale, 1.3, F).
F = @sans_roman_13.

font <-fixed_width: -> bool

@on when every glyph has the same advance, @off when the font is proportional. Determined by comparing the advances of i and w.

font <-default_character: -> char

Character that Pango falls back to when asked to render a glyph the font does not contain (typically ? or a tofu box).

font <-domain: family=[bool] -> tuple

Range of code points the font can render, returned as tuple(Lo, Hi). With family = @on (default) the range includes characters covered by Pango's family fallbacks; with family = @off only the chosen face is considered.

font <-pango_property: int|name -> {description,family,style,weight,size}

Properties of the resolved Pango font. The reported family may differ from the font<-family slot, because font<-family is first mapped through @font_families and the result is then passed to Pango's own font matcher. The reported size is scaled by font.scale.

font <-lookup: family=name, style=name, points=[int], weight=[name|int] -> font

Find an existing font in @fonts matching the arguments, or fail. Mirrors font->initialise; used by the type-checker to deduplicate constructions.

font <-convert: name -> font

Type-checker hook. Accepts:

• the legacy reference syntax @<family>_<style>_<points> (kept for compatibility with code that wrote fonts out by reference);
• any alias name registered in @font_aliases (the recommended form for new code).

  Anything not matched here fails; callers that want to build fonts from family/style/points/weight should construct the font(...) term explicitly.