Module embedded_graphics::mono_font::mapping

Expand description

Glyph mapping.

A glyph mapping defines the position of characters in a MonoFont image. This module provides predefined mappings for common glyph subsets, but custom mappings are also supported.

Custom mappings

Custom mappings can be defined in three different ways:

The StrGlyphMapping type can be used to specify a character mapping by encoding the mapping as a string.
The GlyphMapping trait is implemented for all functions Fn(char) -> usize.
The GlyphMapping trait can be implemented by a custom type.

`StrGlyphMapping` encoding

Strings without a \0 character can be used to directly map a character to its position in the mapping string:

use embedded_graphics::mono_font::mapping::{GlyphMapping, StrGlyphMapping};

let mapping = StrGlyphMapping::new("abcdef1234", 0);
assert_eq!(mapping.index('a'), 0);
assert_eq!(mapping.index('b'), 1);
assert_eq!(mapping.index('1'), 6);
assert_eq!(mapping.index('2'), 7);

This direct mapping is inefficient for mappings that map consecutive ranges of characters to consecutive index ranges. To define a range of characters a \0 character followed by the start and end characters of the inclusive range can be used. This way the mapping in the previous example can be abbreviated to:

use embedded_graphics::mono_font::mapping::{GlyphMapping, StrGlyphMapping};

let mapping = StrGlyphMapping::new("\0af\014", 0);
assert_eq!(mapping.index('a'), 0);
assert_eq!(mapping.index('b'), 1);
assert_eq!(mapping.index('1'), 6);
assert_eq!(mapping.index('2'), 7);