Struct BitmapFont 

pub struct BitmapFont { /* private fields */ }

A 1-bit-per-pixel bitmap glyph font.

Copy because it is just a static reference plus a few small fields.

Implementations

impl BitmapFont

pub const fn new( data: &'static [u8], glyph_width: u8, glyph_height: u8, glyph_count: u16, ) -> Self

Constructs a bitmap font from a static byte slice, mapped through the built-in CP437 char encoding.

data must contain exactly glyph_count * glyph_height bytes.

pub const fn with_charset( data: &'static [u8], glyph_width: u8, glyph_height: u8, glyph_count: u16, charset: &'static [(char, u8)], ) -> Self

Constructs a bitmap font from a static byte slice, mapped through an explicit char -> glyph-index charset instead of the built-in CP437 encoding.

This is how a font extends coverage past CP437: glyph_index looks a char up in charset instead of the CP437 table, so a font built this way can answer for codepoints (quadrants, sextants, braille, …) that CP437 has no mapping for at all. data must contain exactly glyph_count * glyph_height bytes.

charset is scanned linearly, so it is meant for the focused repertoire a font actually declares (a few dozen block or marker glyphs), not for a second general-purpose encoding table.

pub fn rows(&self, index: u8) -> &[u8]

Returns the row bytes for glyph index.

Each byte is one row; bit 7 (MSB) is the leftmost pixel.

Panics

Panics if index as u16 >= self.glyph_count.

pub fn glyph_pixels(&self, index: u8) -> impl Iterator<Item = (u8, u8)> + '_

Iterates the set (“on”) pixels of glyph index as (x, y) coordinates, row-major from the top: x in 0..glyph_width, y in 0..glyph_height.

This is the single place the 1-bit format’s MSB-first bit order lives (pixel x of a row is bit glyph_width - 1 - x of that row’s byte), so consumers (the GL atlas builder, the software rasterizer’s glyph blit) decode through it instead of each re-deriving the shift and risking disagreement. It is also the one seam that has to change for wider-than-8px glyphs (multi-byte rows, #164): today a row is a single byte (glyph_width <= 8), so its bits are read straight out of that byte.

A glyph_width above 8 is out of this format’s contract (rows are one byte, so only bits 0..8 exist); it is clamped to 8 here rather than shifting past the byte’s width, so columns 8.. of an oversized font are simply never yielded instead of panicking.

Panics

Panics if index as u16 >= self.glyph_count (via rows).

pub const fn glyph_width(&self) -> u8

The width of each glyph in pixels (≤ 8 for single-byte rows).

pub const fn glyph_height(&self) -> u8

The height of each glyph in pixels; also bytes per glyph.

pub const fn glyph_count(&self) -> u16

The total number of glyphs stored in this font.

Glyph indices 0..glyph_count() are valid arguments to rows. A GPU backend uses this to size its glyph atlas (one texture-array layer per glyph).

pub const fn glyph_index(&self, ch: char) -> Option<u8>

Maps a Unicode char to a glyph index in this font, or None if this font does not cover ch.

If this font was built with with_charset, ch is looked up in that explicit table; otherwise it goes through the built-in CP437 mapping. A miss is either ch not being in this font’s repertoire at all, or its mapped index falling outside this font’s glyph_count (e.g. a font built with fewer than 256 glyphs).

A returned index is always < glyph_count(), so it is always a valid argument to rows and glyph_pixels.

Substituting something drawable for a miss is FontChain::resolve’s job, not this one’s: a font cannot answer for a character it has no glyph for, and pretending otherwise is what hides a chain’s later fonts from ever being consulted.

Trait Implementations

impl Clone for BitmapFont

fn clone(&self) -> BitmapFont

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for BitmapFont

impl Debug for BitmapFont

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for BitmapFont

impl From<BitmapFont> for FontChain<'static>

fn from(font: BitmapFont) -> Self

Converts to this type from the input type.

impl PartialEq for BitmapFont

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.