Expresso.Element.Diagram.Font (expresso v0.1.0)

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The font that a tool gets for the text of a graph

Each tool measures a text with the font that it gets, and it calculates the size of each box from that measure. Therefore the render gives the font of the slide to the tool, and the browser shows the text in the same font.

The built-in theme uses Atkinson Hyperlegible. The document holds that font as WOFF2 files, and the tools read TTF files, so assets/fonts/ also holds the four TTF files of the font. This module reads them at compile time, as Expresso.Font reads the WOFF2 files, so a release does not need the assets/ directory.

The font option of a diagram gives a directory with the TTF files of a different font. read!/1 takes the family and the style of each file from the name table of the file. A style that the directory does not have takes the regular file.

Summary

Types

t()

A font: its family, and the bytes of the TTF file of each style

Functions

advances(font, text)

The advance width of each character of text in each style of a font

builtin()

The font of the built-in theme, Atkinson Hyperlegible

files(font)

The files of a font, with a name for each style

names(ttf)

The family and the style of a TTF file, from its name table

read!(dir)

Read the TTF files of a directory

Types

t()

@type t() :: %{
  family: String.t(),
  regular: binary(),
  bold: binary(),
  italic: binary(),
  bold_italic: binary()
}

A font: its family, and the bytes of the TTF file of each style

Functions

advances(font, text)

@spec advances(t(), String.t()) :: %{
  required(String.t()) => %{required(String.t()) => float()}
}

The advance width of each character of text in each style of a font

The width is a part of the size of the font, such as 0.55 for a character that is a little more than half of an em wide. The keys of the result are the styles of Pele: 0 regular, 1 bold, 2 italic and 3 bold italic. Each style maps the code point of a character to its width. A character that the font does not have is not in the map, and a measurer gives it a default width. The widths ignore kerning.

Expresso.Element.Diagram.Pele gives the widths to its measurer, so Pele sizes each box for the text in the font of the slide.

builtin()

@spec builtin() :: t()

The font of the built-in theme, Atkinson Hyperlegible

files(font)

@spec files(t()) :: [{String.t(), binary()}]

The files of a font, with a name for each style

A tool reads them from its private directory.

names(ttf)

@spec names(binary()) :: {String.t(), String.t()}

The family and the style of a TTF file, from its name table

The family is the name with the id 1, and the style is the name with the id 2, such as {"Atkinson Hyperlegible", "Bold"}. The function prefers the names for Windows, in UTF-16, and it takes the names for the Mac when the file has no other.

read!(dir)

@spec read!(Path.t()) :: t()

Read the TTF files of a directory

The function raises an ArgumentError for a directory without a TTF file with the style Regular, and for files of more than one family.