Struct Glyph

pub struct Glyph {
    pub id: u16,
    pub style: FontStyle,
    pub symbol: CompactString,
    pub pixel_coords: (i32, i32),
    pub is_emoji: bool,
}

Represents a single character glyph in a font atlas texture.

A Glyph contains the metadata needed to locate and identify a character within a font atlas texture. Each glyph has a unique ID that maps to its coordinates in a WebGL TEXTURE_2D_ARRAY.

ASCII Optimization

For ASCII characters, the glyph ID directly corresponds to the character’s ASCII value, enabling fast lookups without hash table lookups. Non-ASCII characters are assigned sequential IDs starting from a base value.

Glyph ID Bit Layout (16-bit)

Bit(s)	Flag Name	Hex Mask	Binary Mask	Description
0-8	GLYPH_ID	0x01FF	0000_0001_1111_1111	Base glyph identifier
9	BOLD	0x0200	0000_0010_0000_0000	Bold font style
10	ITALIC	0x0400	0000_0100_0000_0000	Italic font style
11	EMOJI	0x0800	0000_1000_0000_0000	Emoji character flag
12	UNDERLINE	0x1000	0001_0000_0000_0000	Underline effect
13	STRIKETHROUGH	0x2000	0010_0000_0000_0000	Strikethrough effect
14-15	RESERVED	0xC000	1100_0000_0000_0000	Reserved for future use

• The first 9 bits (0-8) represent the base glyph ID, allowing for 512 unique glyphs.
• Emoji glyphs implicitly clear any other font style bits.
• The fragment shader uses the glyph ID to decode the texture coordinates and effects.

Glyph ID Encoding Examples

Character	Style	Binary Representation	Hex Value	Description
‘A’ (0x41)	Normal	0000_0000_0100_0001	0x0041	Plain ‘A’
‘A’ (0x41)	Bold	0000_0010_0100_0001	0x0241	Bold ‘A’
‘A’ (0x41)	Bold + Italic	0000_0110_0100_0001	0x0641	Bold italic ‘A’
‘A’ (0x41)	Bold + Underline	0000_1010_0100_0001	0x0A41	Bold underlined ‘A’
‘🚀’ (0x81)	Emoji	1000_0000_1000_0001	0x0881	“rocket” emoji

Fields

id: u16

The glyph ID; encodes the 3d texture coordinates

style: FontStyle

The style of the glyph, e.g., bold, italic

symbol: CompactString

The character

pixel_coords: (i32, i32)

The pixel coordinates of the glyph in the texture

is_emoji: bool

Indicates if the glyph is an emoji

Implementations

impl Glyph

pub const UNASSIGNED_ID: u16 = 65_535u16

The ID is used as a short-lived placeholder until the actual ID is assigned.

pub const GLYPH_ID_MASK: u16 = 511u16

Glyph ID mask - extracts the base glyph identifier (bits 0-8). Supports 512 unique base glyphs (0x000 to 0x1FF) in the texture atlas.

pub const BOLD_FLAG: u16 = 512u16

Bold flag - selects the bold variant of the glyph from the texture atlas.

pub const ITALIC_FLAG: u16 = 1_024u16

Italic flag - selects the italic variant of the glyph from the texture atlas.

pub const EMOJI_FLAG: u16 = 2_048u16

Emoji flag - indicates this glyph represents an emoji character requiring special handling.

pub const UNDERLINE_FLAG: u16 = 4_096u16

Underline flag - renders a horizontal line below the character baseline.

pub const STRIKETHROUGH_FLAG: u16 = 8_192u16

Strikethrough flag - renders a horizontal line through the middle of the character.

impl Glyph

pub fn new(symbol: &str, style: FontStyle, pixel_coords: (i32, i32)) -> Self

Creates a new glyph with the specified symbol and pixel coordinates.

pub fn new_with_id( base_id: u16, symbol: &str, style: FontStyle, pixel_coords: (i32, i32), ) -> Self

pub fn is_ascii(&self) -> bool

Returns true if this glyph represents a single ASCII character.

Trait Implementations

impl Debug for Glyph

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

Formats the value using the given formatter.

impl PartialEq for Glyph

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Glyph

impl StructuralPartialEq for Glyph