Module: TokenReel::Fonts

Defined in:
lib/token_reel/fonts.rb

Overview

Picks and validates the monospace font ImageMagick renders text with. This matters more than it sounds: the whole layout (column wrapping, cursor placement, and the per-span x-offsets syntax highlighting draws at) assumes every glyph is the same width, which is only true if the font actually resolves to a real monospace font. ImageMagick silently falls back to some default font (and only warns on stderr, without failing) when asked for a font name it doesn't know -- so guessing a hardcoded name and trusting it works is how you end up with misaligned, overlapping text.

Constant Summary collapse

CANDIDATES =

Common monospace font names, in priority order, as ImageMagick tends to expose them across Linux/macOS/Windows installs.

%w[
  DejaVu-Sans-Mono Menlo-Regular Consolas Liberation-Mono
  Courier-New Monaco Andale-Mono PT-Mono Noto-Sans-Mono
  Ubuntu-Mono Cascadia-Mono JetBrains-Mono JetBrainsMono-Regular
  Fira-Code FiraCode-Regular Hack-Regular Courier fixed
].freeze

Class Method Summary collapse

Class Method Details

.autodetect ⇒ Object 



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# File 'lib/token_reel/fonts.rb', line 40

def self.autodetect
  CANDIDATES.find { |name| available.include?(name) } ||
    raise(RenderError,
          "no monospace font found on this system; install one of " \
          "#{CANDIDATES.first(4).join(', ')}, etc., or pass --font NAME " \
          "with an exact name from `#{Renderer.convert_binary} -list font`")
end

.available ⇒ Object 



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# File 'lib/token_reel/fonts.rb', line 23

def self.available
  @available ||= `#{Shellwords.escape(Renderer.convert_binary)} -list font 2>/dev/null`
                 .scan(/^\s*Font:\s*(\S+)/).flatten
end

.resolve!(name) ⇒ Object

name == nil means "pick one for me". A name the caller passed in explicitly is validated against what ImageMagick actually knows, rather than trusted -- see the module comment for why.

Raises:



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# File 'lib/token_reel/fonts.rb', line 31

def self.resolve!(name)
  return autodetect if name.nil?
  return name if available.include?(name)

  raise RenderError,
        "font #{name.inspect} not found via `#{Renderer.convert_binary} -list font` " \
        "(pass --font with an exact name from that list, or omit --font to auto-detect)"
end