a truetype font More...

#include <font.h>

Classes
struct	glyph
struct	atlas_region
	a rectangle of the atlas, in texels More...

Public Member Functions
const glyph *	try_get (char32_t aCodepoint)
	the glyph for a codepoint or nullptr when the atlas has no room left for it.
const glyph &	fallback () const
	the font's .notdef glyph, which most fonts draw as a visible box.
void	clear ()
	empties the atlas back to the size it was constructed with.
float	kerning (char32_t aLeft, char32_t aRight) const
	additional spacing between two adjacent codepoints in pixels.
texture_data::view	atlas () const
	view of the atlas texture
std::optional< atlas_region >	atlas_changed_since (std::size_t aGeneration) const
	which part of the atlas has changed since a given generation.
std::size_t	atlas_generation () const
	a number that changes whenever the atlas does.
float	line_height () const
	baseline to baseline distance in pixels
float	ascent () const
	baseline to the top of the tallest glyph, in pixels
float	descent () const
	baseline to the bottom of the lowest glyph, in pixels. Negative.
	font (std::span< const texture_data::encoded_byte > aTrueTypeData, float aPixelSize, font_settings aSettings={})
	builds a font from the contents of a truetype or opentype file, or a collection
std::size_t	atlas_edge () const
	the atlas's current edge length in texels. Changes when the atlas grows.
	font (font &&) noexcept
font &	operator= (font &&) noexcept
	font (const font &)=delete
font &	operator= (const font &)=delete

Detailed Description

a truetype font

Glyphs are rasterised the first time they are asked for and packed into a single atlas texture, rather than a fixed set dont up front.

The atlas is a single channel (texture_data::format::grey) coverage map. Upload it to a texture with atlas(), and re-upload when atlas_generation() differs from the one last uploaded.

Constructor & Destructor Documentation

◆ font()

gdk::graphics::ext::font::font	(	std::span< const texture_data::encoded_byte >	aTrueTypeData,
		float	aPixelSize,
		font_settings	aSettings = {} )

builds a font from the contents of a truetype or opentype file, or a collection

Parameters

aTrueTypeData	the bytes of a .ttf, .otf, .ttc or .otc. Copied: the font owns its own copy for its lifetime
aPixelSize	the size to rasterise at, in pixels. Of what is aSettings.sizing: ascent to descent unless told otherwise
aSettings	the face, the sizing and the atlas's bounds, all defaulted.

Member Function Documentation

◆ clear()

void gdk::graphics::ext::font::clear ( )

empties the atlas back to the size it was constructed with.

Warning: every texture coordinate previously handed out becomes stale, exactly as when the atlas grows. Safe between frames, not part way through laying text out.

◆ fallback()

const glyph & gdk::graphics::ext::font::fallback ( ) const

nodiscard

the font's .notdef glyph, which most fonts draw as a visible box.

Always present: it is rasterised at construction and put back after every growth and every clear, so it is there to draw even when nothing else will fit. A caller that wants tofu where try_get() came back empty asks for it, rather than being handed it silently.

◆ try_get()

const glyph * gdk::graphics::ext::font::try_get ( char32_t aCodepoint )

nodiscard

the glyph for a codepoint or nullptr when the atlas has no room left for it.

Warning: the pointer is invalidated by a later call that rasterises something new

The documentation for this class was generated from the following file:

/home/runner/work/gdk-graphics/gdk-graphics/data/include/gdk/graphics/ext/font.h

Classes