i_slint_renderer_software/
fonts.rs

1// Copyright © SixtyFPS GmbH <info@slint.dev>
2// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0
3
4use alloc::rc::Rc;
5use alloc::vec::Vec;
6use core::cell::RefCell;
7
8use super::{Fixed, PhysicalLength, PhysicalSize};
9use i_slint_core::Coord;
10use i_slint_core::graphics::{BitmapFont, FontRequest};
11use i_slint_core::lengths::{LogicalLength, ScaleFactor};
12use i_slint_core::textlayout::TextLayout;
13
14i_slint_core::thread_local! {
15    static BITMAP_FONTS: RefCell<Vec<&'static BitmapFont>> = RefCell::default()
16}
17
18#[derive(derive_more::From, Clone)]
19pub enum GlyphAlphaMap {
20    Static(&'static [u8]),
21    Shared(Rc<[u8]>),
22}
23
24#[derive(Clone)]
25pub struct RenderableGlyph {
26    pub x: Fixed<i32, 8>,
27    pub y: Fixed<i32, 8>,
28    pub width: PhysicalLength,
29    pub height: PhysicalLength,
30    pub alpha_map: GlyphAlphaMap,
31    pub pixel_stride: u16,
32    pub sdf: bool,
33}
34
35impl RenderableGlyph {
36    pub fn size(&self) -> PhysicalSize {
37        PhysicalSize::from_lengths(self.width, self.height)
38    }
39}
40
41// Subset of `RenderableGlyph`, specfically for VectorFonts.
42#[cfg(feature = "systemfonts")]
43#[derive(Clone)]
44pub struct RenderableVectorGlyph {
45    pub x: Fixed<i32, 8>,
46    pub y: Fixed<i32, 8>,
47    pub width: PhysicalLength,
48    pub height: PhysicalLength,
49    pub alpha_map: Rc<[u8]>,
50    pub pixel_stride: u16,
51    pub bounds: fontdue::OutlineBounds,
52}
53
54#[cfg(feature = "systemfonts")]
55impl RenderableVectorGlyph {
56    pub fn size(&self) -> PhysicalSize {
57        PhysicalSize::from_lengths(self.width, self.height)
58    }
59}
60
61pub trait GlyphRenderer {
62    fn render_glyph(&self, glyph_id: core::num::NonZeroU16) -> Option<RenderableGlyph>;
63    /// The amount of pixel in the original image that correspond to one pixel in the rendered image
64    fn scale_delta(&self) -> Fixed<u16, 8>;
65}
66
67pub(super) const DEFAULT_FONT_SIZE: LogicalLength = LogicalLength::new(12 as Coord);
68
69mod pixelfont;
70#[cfg(feature = "systemfonts")]
71pub mod vectorfont;
72
73#[cfg(feature = "systemfonts")]
74pub mod systemfonts;
75
76#[derive(derive_more::From)]
77pub enum Font {
78    PixelFont(pixelfont::PixelFont),
79    #[cfg(feature = "systemfonts")]
80    VectorFont(vectorfont::VectorFont),
81}
82
83/// Returns the size of the pre-rendered font in pixels.
84pub fn pixel_size(glyphs: &i_slint_core::graphics::BitmapGlyphs) -> PhysicalLength {
85    PhysicalLength::new(glyphs.pixel_size)
86}
87
88impl i_slint_core::textlayout::FontMetrics<PhysicalLength> for Font {
89    fn ascent(&self) -> PhysicalLength {
90        match self {
91            Font::PixelFont(pixel_font) => pixel_font.ascent(),
92            #[cfg(feature = "systemfonts")]
93            Font::VectorFont(vector_font) => vector_font.ascent(),
94        }
95    }
96
97    fn height(&self) -> PhysicalLength {
98        match self {
99            Font::PixelFont(pixel_font) => pixel_font.height(),
100            #[cfg(feature = "systemfonts")]
101            Font::VectorFont(vector_font) => vector_font.height(),
102        }
103    }
104
105    fn descent(&self) -> PhysicalLength {
106        match self {
107            Font::PixelFont(pixel_font) => pixel_font.descent(),
108            #[cfg(feature = "systemfonts")]
109            Font::VectorFont(vector_font) => vector_font.descent(),
110        }
111    }
112
113    fn x_height(&self) -> PhysicalLength {
114        match self {
115            Font::PixelFont(pixel_font) => pixel_font.x_height(),
116            #[cfg(feature = "systemfonts")]
117            Font::VectorFont(vector_font) => vector_font.x_height(),
118        }
119    }
120
121    fn cap_height(&self) -> PhysicalLength {
122        match self {
123            Font::PixelFont(pixel_font) => pixel_font.cap_height(),
124            #[cfg(feature = "systemfonts")]
125            Font::VectorFont(vector_font) => vector_font.cap_height(),
126        }
127    }
128}
129
130pub fn match_font(request: &FontRequest, scale_factor: ScaleFactor) -> Font {
131    let requested_weight = request
132        .weight
133        .and_then(|weight| weight.try_into().ok())
134        .unwrap_or(/* CSS normal */ 400);
135
136    let bitmap_font = BITMAP_FONTS.with(|fonts| {
137        let fonts = fonts.borrow();
138
139        request.family.as_ref().and_then(|requested_family| {
140            fonts
141                .iter()
142                .filter(|bitmap_font| {
143                    core::str::from_utf8(bitmap_font.family_name.as_slice()).unwrap()
144                        == requested_family.as_str()
145                        && bitmap_font.italic == request.italic
146                })
147                .min_by_key(|bitmap_font| bitmap_font.weight.abs_diff(requested_weight))
148                .copied()
149        })
150    });
151
152    let font = match bitmap_font {
153        Some(bitmap_font) => bitmap_font,
154        None => {
155            #[cfg(feature = "systemfonts")]
156            if let Some(vectorfont) = systemfonts::match_font(request, scale_factor) {
157                return vectorfont.into();
158            }
159            if let Some(fallback_bitmap_font) = BITMAP_FONTS.with(|fonts| {
160                let fonts = fonts.borrow();
161                fonts
162                    .iter()
163                    .cloned()
164                    .filter(|bitmap_font| bitmap_font.italic == request.italic)
165                    .min_by_key(|bitmap_font| bitmap_font.weight.abs_diff(requested_weight))
166                    .or_else(|| fonts.first().cloned())
167            }) {
168                fallback_bitmap_font
169            } else {
170                #[cfg(feature = "systemfonts")]
171                return systemfonts::fallbackfont(request, scale_factor).into();
172                #[cfg(not(feature = "systemfonts"))]
173                panic!(
174                    "No font fallback found. The software renderer requires enabling the `EmbedForSoftwareRenderer` option when compiling slint files."
175                )
176            }
177        }
178    };
179
180    let requested_pixel_size: PhysicalLength =
181        (request.pixel_size.unwrap_or(DEFAULT_FONT_SIZE).cast() * scale_factor).cast();
182
183    let nearest_pixel_size = font
184        .glyphs
185        .partition_point(|glyphs| pixel_size(glyphs) <= requested_pixel_size)
186        .saturating_sub(1);
187    let matching_glyphs = &font.glyphs[nearest_pixel_size];
188
189    let pixel_size = if font.sdf { requested_pixel_size } else { pixel_size(matching_glyphs) };
190
191    pixelfont::PixelFont { bitmap_font: font, glyphs: matching_glyphs, pixel_size }.into()
192}
193
194pub fn text_layout_for_font<'a, Font>(
195    font: &'a Font,
196    font_request: &FontRequest,
197    scale_factor: ScaleFactor,
198) -> TextLayout<'a, Font>
199where
200    Font: i_slint_core::textlayout::AbstractFont
201        + i_slint_core::textlayout::TextShaper<Length = PhysicalLength>,
202{
203    let letter_spacing =
204        font_request.letter_spacing.map(|spacing| (spacing.cast() * scale_factor).cast());
205
206    TextLayout { font, letter_spacing }
207}
208
209pub fn register_bitmap_font(font_data: &'static BitmapFont) {
210    BITMAP_FONTS.with(|fonts| fonts.borrow_mut().push(font_data))
211}
i_slint_renderer_software/fonts.rs

i_slint_renderer_software/
fonts.rs
