slint/internal/core/graphics/bitmapfont.rs
Olivier Goffart 4e7bbcf2ba
Try to improve rendering (positioning) of signed field distance font. (#6868)
* WIP: swrenderer: use fixed point for the pixmap font coordinate

* swrenderer: signed distance field: move the glyph to the middle

* swrenderer: round the advance instead of truncating it in distance field

* swrenderer: actually align the gplyph on the sub-pixel precision

sub-pixel within the source.

* swrenderer: adapt the threshold for signed distance field

sqrt(2) is the distance to the diagonal, seems like this gives sharper fonts

* Fix bug in the elision, and re-upload the screenshort

the screenshot changed because the afvanced is now rounded intead of
truncated
2024-11-30 23:03:31 +01:00

76 lines
2.9 KiB
Rust

// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0
use crate::slice::Slice;
#[repr(C)]
#[derive(Debug)]
/// A pre-rendered glyph with the alpha map and associated metrics
pub struct BitmapGlyph {
/// The starting x-coordinate for the glyph, relative to the base line
/// This is a fixed point number that is shifted by 6 bits
pub x: i16,
/// The starting y-coordinate for the glyph, relative to the base line
/// This is a fixed point number that is shifted by 6 bits
pub y: i16,
/// The width of the glyph in pixels
pub width: i16,
/// The height of the glyph in pixels
pub height: i16,
/// The horizontal distance to the next glyph
/// This is a fixed point number that is shifted by 6 bits
pub x_advance: i16,
/// The 8-bit alpha map that's to be blended with the current text color
/// or 8-bit signed distance field depending on `BitmapFont::sdf`
pub data: Slice<'static, u8>,
}
#[repr(C)]
#[derive(Debug)]
/// A set of pre-rendered bitmap glyphs at a fixed pixel size
pub struct BitmapGlyphs {
/// The font size in pixels at which the glyphs were pre-rendered. The boundaries of glyphs may exceed this
/// size, if the font designer has chosen so. This is only used for matching.
pub pixel_size: i16,
/// The data of the pre-rendered glyphs
pub glyph_data: Slice<'static, BitmapGlyph>,
}
#[repr(C)]
#[derive(Debug)]
/// An entry in the character map of a [`BitmapFont`].
pub struct CharacterMapEntry {
/// The unicode code point for a given glyph
pub code_point: char,
/// The corresponding index in the `glyph_data` of [`BitmapGlyphs`]
pub glyph_index: u16,
}
#[repr(C)]
#[derive(Debug)]
/// A subset of an originally scalable font that's rendered ahead of time.
pub struct BitmapFont {
/// The family name of the font
pub family_name: Slice<'static, u8>,
/// A vector of code points and their corresponding glyph index, sorted by code point.
pub character_map: Slice<'static, CharacterMapEntry>,
/// The font supplied size of the em square.
pub units_per_em: f32,
/// The font ascent in design metrics (typically positive)
pub ascent: f32,
/// The font descent in design metrics (typically negative)
pub descent: f32,
/// The font's x-height.
pub x_height: f32,
/// The font's cap-height.
pub cap_height: f32,
/// A vector of pre-rendered glyph sets. Each glyph set must have the same number of glyphs,
/// which must be at least as big as the largest glyph index in the character map.
pub glyphs: Slice<'static, BitmapGlyphs>,
/// The weight of the font in CSS units (400 is normal).
pub weight: u16,
/// Whether the type-face is rendered italic.
pub italic: bool,
/// Whether the format of the font is a signed distance field
pub sdf: bool,
}