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linux-fonts

X11 core font loading, querying, metrics, measurement, and caching for Linux.

Uses Xlib's built-in font functions (XLoadQueryFont, XLoadFont, XSetFont, XTextWidth, XFreeFont, etc.) to provide an Oak-friendly font API on Linux.

Dependencies

  • sys, writes, linux-core, linux-loader

Xlib Font Wrappers

loadQueryFont(display, name) -> result

Loads and queries an X11 core font by name (XLFD or alias). Returns { type: :ok, fontStruct: <ptr> }.

loadFont(display, name) -> result

Loads an X11 font and returns its Font XID. Returns { type: :ok, fontId }.

setFont(display, gc, fontId)

Sets the font for a graphics context.

freeFont(display, fontStruct)

Releases an XFontStruct.

unloadFont(display, fontId)

Unloads a font loaded via loadFont.

Text Measurement

textWidth(fontStruct, text) -> result

Pixel width via XTextWidth. Returns { type: :ok, width }.

XFontStruct Field Accessors

fontStructAscent(fontStruct) -> int

fontStructDescent(fontStruct) -> int

fontStructHeight(fontStruct) -> int

fontStructFid(fontStruct) -> int

Higher-Level Helpers

fontMetrics(display, name) -> result

Loads a font and returns its metrics: { type: :ok, fontStruct, fontId, ascent, descent, height }

measureText(display, fontName, text) -> result

Loads a font, measures the text, and returns: { type: :ok, fontStruct, width, height, ascent, descent }

The font remains loaded — call freeFont when done.

Font Cache

cachedFont(display, fontName) -> result

Returns a cached XFontStruct, loading on first access.

releaseCachedFonts(display)

Frees all cached fonts for a given display.

releaseAllCachedFonts()

Frees every cached font entry globally.

Well-Known Font Names

Constant Value
FONT_FIXED 'fixed'
FONT_CURSOR 'cursor'
FONT_6X13 '6x13'
FONT_9X15 '9x15'
FONT_10X20 '10x20'
FONT_COURIER_14 '-*-courier-medium-r-normal--14-*-...-iso8859-1'
FONT_HELV_12 '-*-helvetica-medium-r-normal--12-*-...-iso8859-1'
FONT_TIMES_14 '-*-times-medium-r-normal--14-*-...-iso8859-1'

buildXLFD(spec) -> string

Constructs an X Logical Font Description from a spec:

xlfd := lf.buildXLFD({
    family: 'courier'
    weight: 'bold'
    slant: 'r'
    pixelSize: 14
    registry: 'iso8859'
    encoding: '1'
})
// -> '-*-courier-bold-r-*-*-14-*-*-*-*-*-iso8859-1'

Example

lf := import('linux-fonts')

// Load a font and measure text
metrics := lf.fontMetrics(display, '9x15')
if metrics.type = :ok -> {
    w := lf.textWidth(metrics.fontStruct, 'Hello, world!')
    // w.width is the pixel width
    lf.freeFont(display, metrics.fontStruct)
}

// Using the cache
cached := lf.cachedFont(display, 'fixed')
if cached.type = :ok -> {
    lf.setFont(display, gc, lf.fontStructFid(cached.fontStruct))
}
lf.releaseCachedFonts(display)