slint/internal/compiler/passes/embed_glyphs.rs

// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-1.0 OR LicenseRef-Slint-commercial

use crate::diagnostics::BuildDiagnostics;
#[cfg(not(target_arch = "wasm32"))]
use crate::embedded_resources::{BitmapFont, BitmapGlyph, BitmapGlyphs, CharacterMapEntry};
#[cfg(not(target_arch = "wasm32"))]
use crate::expression_tree::BuiltinFunction;
use crate::expression_tree::{Expression, Unit};
use crate::object_tree::*;
use std::collections::HashSet;
use std::rc::Rc;

use i_slint_common::sharedfontdb::{self, fontdb};

#[derive(Clone, derive_more::Deref)]
struct Font {
    id: fontdb::ID,
    #[deref]
    fontdue_font: fontdue::Font,
}

#[cfg(target_arch = "wasm32")]
pub fn embed_glyphs<'a>(
    _component: &Rc<Component>,
    _scale_factor: f64,
    _pixel_sizes: Vec<i16>,
    _characters_seen: HashSet<char>,
    _all_docs: impl Iterator<Item = &'a crate::object_tree::Document> + 'a,
    _diag: &mut BuildDiagnostics,
) -> bool {
    false
}

#[cfg(not(target_arch = "wasm32"))]
pub fn embed_glyphs<'a>(
    component: &Rc<Component>,
    scale_factor: f64,
    mut pixel_sizes: Vec<i16>,
    mut characters_seen: HashSet<char>,
    all_docs: impl Iterator<Item = &'a crate::object_tree::Document> + 'a,
    diag: &mut BuildDiagnostics,
) {
    use crate::diagnostics::Spanned;

    let generic_diag_location =
        component.root_element.borrow().node.as_ref().map(|e| e.to_source_location());

    characters_seen.extend(
        ('a'..='z')
            .chain('A'..='Z')
            .chain('0'..='9')
            .chain(" '!\"#$%&'()*+,-./:;<=>?@\\]^_|~".chars())
            .chain(std::iter::once('●'))
            .chain(std::iter::once('…')),
    );

    if let Ok(sizes_str) = std::env::var("SLINT_FONT_SIZES") {
        for custom_size_str in sizes_str.split(',') {
            let custom_size = if let Ok(custom_size) = custom_size_str
                .parse::<f64>()
                .map(|size_as_float| (size_as_float * scale_factor) as i16)
            {
                custom_size
            } else {
                diag.push_error(
                    format!(
                        "Invalid font size '{}' specified in `SLINT_FONT_SIZES`",
                        custom_size_str
                    ),
                    &generic_diag_location,
                );
                return;
            };

            if let Err(pos) = pixel_sizes.binary_search(&custom_size) {
                pixel_sizes.insert(pos, custom_size)
            }
        }
    }

    sharedfontdb::FONT_DB.with(|db| {
        let mut fontdb = db.borrow_mut();

        embed_glyphs_with_fontdb(
            &mut fontdb,
            component,
            pixel_sizes,
            characters_seen,
            all_docs,
            diag,
            generic_diag_location,
        );
    })
}

fn embed_glyphs_with_fontdb<'a>(
    fontdb: &mut sharedfontdb::FontDatabase,
    component: &Rc<Component>,
    pixel_sizes: Vec<i16>,
    characters_seen: HashSet<char>,
    all_docs: impl Iterator<Item = &'a crate::object_tree::Document> + 'a,
    diag: &mut BuildDiagnostics,
    generic_diag_location: Option<crate::diagnostics::SourceLocation>,
) {
    let fallback_fonts = get_fallback_fonts(fontdb);

    let mut custom_fonts = Vec::new();

    // add custom fonts
    for doc in all_docs {
        for (font_path, import_token) in doc.custom_fonts.iter() {
            let face_count = fontdb.faces().count();
            if let Err(e) = fontdb.load_font_file(&font_path) {
                diag.push_error(format!("Error loading font: {}", e), import_token);
            } else {
                custom_fonts.extend(fontdb.faces().skip(face_count).map(|info| info.id))
            }
        }
    }

    let default_font_ids = if !fontdb.default_font_family_ids.is_empty() {
        fontdb.default_font_family_ids.clone()
    } else {
        let (family, source_location) = component
            .root_element
            .borrow()
            .bindings
            .get("default-font-family")
            .and_then(|binding| match &binding.borrow().expression {
                Expression::StringLiteral(family) => {
                    Some((Some(family.clone()), binding.borrow().span.clone()))
                }
                _ => None,
            })
            .unwrap_or_default();

        match fontdb.query_with_family(Default::default(), family.as_deref()) {
            Some(id) => vec![id],
            None => {
                if let Some(source_location) = source_location {
                    diag.push_error_with_span(format!("could not find font that provides specified family, falling back to Sans-Serif"), source_location);
                } else {
                    diag.push_error(format!("internal error: fontdb could not determine a default font for sans-serif"), &generic_diag_location);
                };
                return;
            }
        }
    };

    let default_font_paths = default_font_ids
        .iter()
        .map(|id| {
            let (source, _) =
                fontdb.face_source(*id).expect("internal error: fontdb provided ids are not valid");
            match source {
                fontdb::Source::Binary(_) => unreachable!(),
                fontdb::Source::File(path_buf) => path_buf,
                fontdb::Source::SharedFile(path_buf, _) => path_buf,
            }
            .clone()
        })
        .collect::<Vec<std::path::PathBuf>>();

    // Map from path to family name
    let mut fonts = std::collections::BTreeMap::<std::path::PathBuf, fontdb::ID>::new();
    fonts.extend(default_font_paths.iter().cloned().zip(default_font_ids.iter().cloned()));

    // add custom fonts
    let mut custom_face_error = false;
    fonts.extend(custom_fonts.iter().filter_map(|face_id| {
        fontdb.face(*face_id).and_then(|face_info| {
            Some((
                match &face_info.source {
                    fontdb::Source::File(path) => path.clone(),
                    _ => {
                        diag.push_error(
                            "internal error: memory fonts are not supported in the compiler"
                                .to_string(),
                            &generic_diag_location,
                        );
                        custom_face_error = true;
                        return None;
                    }
                },
                *face_id,
            ))
        })
    }));

    if custom_face_error {
        return;
    }

    let mut embed_font_by_path_and_face_id = |path: &std::path::Path, face_id| {
        let maybe_font = if let Some(maybe_font) =
            fontdb.with_face_data(face_id, |font_data, face_index| {
                let fontdue_font = match fontdue::Font::from_bytes(
                    font_data,
                    fontdue::FontSettings { collection_index: face_index, scale: 40. },
                ) {
                    Ok(fontdue_font) => fontdue_font,
                    Err(fontdue_msg) => {
                        diag.push_error(
                            format!(
                                "internal error: fontdue can't parse font {}: {fontdue_msg}", path.display()
                            ),
                            &generic_diag_location,
                        );
                        return None;
                    }
                };

                let family_name = if let Some(family_name) = fontdb
                    .face(face_id)
                    .expect("must succeed as we are within face_data with same face_id")
                    .families
                    .first()
                    .map(|(name, _)| name.clone())
                {
                    family_name
                } else {
                    diag.push_error(
                        format!("internal error: TrueType font without english family name encountered: {}", path.display()),
                        &generic_diag_location,
                    );
                    return None;
                };

                embed_font(
                    fontdb,
                    family_name,
                    Font{ id: face_id, fontdue_font },
                    &pixel_sizes,
                    characters_seen.iter().cloned(),
                    &fallback_fonts,
                )
                .into()
            }) {
            maybe_font
        } else {
            diag.push_error(
                format!("internal error: face_id of selected font {} is unknown to fontdb", path.display()),
                &generic_diag_location,
            );
            return;
        };

        let font = if let Some(font) = maybe_font {
            font
        } else {
            // Diagnostic was created inside callback for `width_face_data`.
            return;
        };

        let resource_id = component.embedded_file_resources.borrow().len();
        component.embedded_file_resources.borrow_mut().insert(
            path.to_string_lossy().to_string(),
            crate::embedded_resources::EmbeddedResources {
                id: resource_id,
                kind: crate::embedded_resources::EmbeddedResourcesKind::BitmapFontData(font),
            },
        );

        component.init_code.borrow_mut().font_registration_code.push(Expression::FunctionCall {
            function: Box::new(Expression::BuiltinFunctionReference(
                BuiltinFunction::RegisterBitmapFont,
                None,
            )),
            arguments: vec![Expression::NumberLiteral(resource_id as _, Unit::None)],
            source_location: None,
        });
    };

    // Make sure to embed the default font first, because that becomes the default at run-time.
    for path in default_font_paths {
        embed_font_by_path_and_face_id(&path, fonts.remove(&path).unwrap());
    }

    for (path, face_id) in &fonts {
        embed_font_by_path_and_face_id(path, *face_id);
    }
}

#[inline(never)] // workaround https://github.com/rust-lang/rust/issues/104099
fn get_fallback_fonts(fontdb: &sharedfontdb::FontDatabase) -> Vec<fontdue::Font> {
    #[allow(unused)]
    let mut fallback_families: Vec<String> = Vec::new();

    #[cfg(target_os = "macos")]
    {
        fallback_families = ["Menlo", "Apple Symbols", "Apple Color Emoji"]
            .into_iter()
            .map(Into::into)
            .collect::<Vec<String>>();
    }

    #[cfg(not(any(
        target_family = "windows",
        target_os = "macos",
        target_os = "ios",
        target_arch = "wasm32"
    )))]
    {
        fallback_families = fontdb.fontconfig_fallback_families.clone();
    }

    let fallback_fonts = fallback_families
        .iter()
        .filter_map(|fallback_family| {
            fontdb
                .query(&fontdb::Query {
                    families: &[fontdb::Family::Name(fallback_family)],
                    ..Default::default()
                })
                .and_then(|face_id| {
                    fontdb
                        .with_face_data(face_id, |face_data, face_index| {
                            fontdue::Font::from_bytes(
                                face_data,
                                fontdue::FontSettings { collection_index: face_index, scale: 40. },
                            )
                            .ok()
                        })
                        .flatten()
                })
        })
        .collect::<Vec<_>>();
    fallback_fonts
}

#[cfg(not(target_arch = "wasm32"))]
fn embed_font(
    fontdb: &fontdb::Database,
    family_name: String,
    font: Font,
    pixel_sizes: &[i16],
    character_coverage: impl Iterator<Item = char>,
    fallback_fonts: &[fontdue::Font],
) -> BitmapFont {
    let mut character_map: Vec<CharacterMapEntry> = character_coverage
        .enumerate()
        .map(|(glyph_index, code_point)| CharacterMapEntry {
            code_point,
            glyph_index: u16::try_from(glyph_index)
                .expect("more than 65535 glyphs are not supported"),
        })
        .collect();
    character_map.sort_by_key(|entry| entry.code_point);

    let glyphs = pixel_sizes
        .iter()
        .map(|pixel_size| {
            let mut glyph_data = Vec::new();
            glyph_data.resize(character_map.len(), Default::default());

            for CharacterMapEntry { code_point, glyph_index } in &character_map {
                let (metrics, bitmap) = core::iter::once(&font.fontdue_font)
                    .chain(fallback_fonts.iter())
                    .find_map(|font| {
                        font.chars()
                            .contains_key(code_point)
                            .then(|| font.rasterize(*code_point, *pixel_size as _))
                    })
                    .unwrap_or_else(|| font.rasterize(*code_point, *pixel_size as _));

                let glyph = BitmapGlyph {
                    x: i16::try_from(metrics.xmin).expect("large glyph x coordinate"),
                    y: i16::try_from(metrics.ymin).expect("large glyph y coordinate"),
                    width: i16::try_from(metrics.width).expect("large width"),
                    height: i16::try_from(metrics.height).expect("large height"),
                    x_advance: i16::try_from(metrics.advance_width as i64)
                        .expect("large advance width"),
                    data: bitmap,
                };
                glyph_data[*glyph_index as usize] = glyph;
            }

            BitmapGlyphs { pixel_size: *pixel_size, glyph_data }
        })
        .collect();

    // Get the basic metrics in design coordinates
    let metrics = font
        .horizontal_line_metrics(font.units_per_em())
        .expect("encountered font without hmtx table");

    let face_info = fontdb.face(font.id).unwrap();

    BitmapFont {
        family_name,
        character_map,
        units_per_em: font.units_per_em(),
        ascent: metrics.ascent,
        descent: metrics.descent,
        glyphs,
        weight: face_info.weight.0,
        italic: if face_info.style == fontdb::Style::Normal { false } else { true },
    }
}

fn try_extract_font_size_from_element(elem: &ElementRc, property_name: &str) -> Option<f64> {
    elem.borrow().bindings.get(property_name).and_then(|expression| {
        match &expression.borrow().expression {
            Expression::NumberLiteral(value, Unit::Px) => Some(*value),
            _ => None,
        }
    })
}

pub fn collect_font_sizes_used(
    component: &Rc<Component>,
    scale_factor: f64,
    sizes_seen: &mut Vec<i16>,
) {
    let mut add_font_size = |logical_size: f64| {
        let pixel_size = (logical_size * scale_factor) as i16;
        match sizes_seen.binary_search(&pixel_size) {
            Ok(_) => {}
            Err(pos) => sizes_seen.insert(pos, pixel_size),
        }
    };

    recurse_elem_including_sub_components(component, &(), &mut |elem, _| match elem
        .borrow()
        .base_type
        .to_string()
        .as_str()
    {
        "TextInput" | "Text" => {
            if let Some(font_size) = try_extract_font_size_from_element(elem, "font-size") {
                add_font_size(font_size)
            }
        }
        "Dialog" | "Window" | "WindowItem" => {
            if let Some(font_size) = try_extract_font_size_from_element(elem, "default-font-size") {
                add_font_size(font_size)
            }
        }
        _ => {}
    });
}

pub fn scan_string_literals(component: &Rc<Component>, characters_seen: &mut HashSet<char>) {
    visit_all_expressions(component, |expr, _| {
        expr.visit_recursive(&mut |expr| {
            if let Expression::StringLiteral(string) = expr {
                characters_seen.extend(string.chars());
            }
        })
    })
}