Merge pull request #172 from storytold/fix/issue-81

Fix #81: Chinese, Japanese and Korean names show in the UI, not boxes

crates/text/src/fontdb.rs

@@ -675,6 +675,13 @@ impl FontDb {
         None
     }
 
+    /// A face that covers `c`, for text drawn outside the canvas (the app's own UI): the loaded
+    /// fonts first, then (native) an installed one, loaded on demand. Characters no font covers
+    /// are remembered, so they are looked for once.
+    pub fn face_covering(&self, c: char) -> Option<Arc<FontFace>> {
+        self.fallback_for(c, 0)
+    }
+
     fn loaded_fallback(&self, c: char, exclude: u32) -> Option<Arc<FontFace>> {
         let faces = self.read_faces();
         let mut order: Vec<&Arc<FontFace>> = faces.iter().filter(|f| f.id != exclude).collect();

crates/ui-egui/src/lib.rs

@@ -33,6 +33,7 @@ pub mod sysclip;
 pub mod theme;
 pub mod titlebar;
 pub mod toolbar;
+mod ui_fonts;
 pub mod unsaved;
 pub mod widgets;
 pub mod workspaces;
@@ -257,6 +258,8 @@ pub struct VectorcraftApp {
     pub synthetic: Vec<egui::Event>,
     styled: bool,
     fonts_ready: bool,
+    /// Installed fonts added to the UI's for characters its own fonts lack (CJK names…).
+    ui_fonts: ui_fonts::UiFonts,
     frame: u64,
     last_time: f64,
     /// Canvas rect of the last frame (screen points), for control-channel coordinate mapping.
@@ -336,6 +339,7 @@ impl VectorcraftApp {
             synthetic: vec![],
             styled: false,
             fonts_ready: false,
+            ui_fonts: Default::default(),
             frame: 0,
             last_time: 0.0,
             canvas_rect: None,
@@ -791,6 +795,7 @@ impl VectorcraftApp {
         if self.custom_titlebar {
             titlebar::resize_zones(ui);
         }
+        self.ui_fonts.frame(&ctx);
         self.perf.frame_ms = now_ms() - t0;
         let _ = json!(null);
     }

crates/ui-egui/src/ui_fonts.rs

@@ -0,0 +1,197 @@
+//! Fallback fonts for the app's own text: layer and file names (and anything else the UI shows) in
+//! Chinese, Japanese, Korean or other scripts the UI fonts lack are drawn in an installed font that
+//! covers them. Nothing is bundled for them: the first time a frame paints a character the UI fonts
+//! don't have, an installed font covering it is looked for (in the background on native) and added
+//! to egui's families as their last fallback, from the next frame on. Text the UI fonts cover costs
+//! no font loading or memory. On the web, which has no system fonts, such characters stay
+//! missing-glyph boxes.
+
+use std::collections::HashSet;
+use std::sync::Arc;
+
+use egui::epaint::Shape;
+use egui::epaint::text::{FontInsert, FontPriority, InsertFontFamily};
+use egui::{FontData, FontFamily, FontId, LayerId};
+use vectorcraft_text::{FontDb, FontFace};
+
+#[derive(Default)]
+pub(crate) struct UiFonts {
+    /// Characters looked at already: the UI fonts have them, a fallback was added (or is being
+    /// looked for), or no font has them.
+    seen: HashSet<char>,
+    /// The fonts added to egui, by name.
+    added: HashSet<String>,
+    /// The faces covering the characters being looked for (native: looked for on a thread).
+    #[cfg(not(target_arch = "wasm32"))]
+    pending: Option<std::sync::mpsc::Receiver<Vec<Arc<FontFace>>>>,
+}
+
+impl UiFonts {
+    /// After a frame is laid out: add the fallback fonts found since the last frame, and look for
+    /// fonts covering the characters this frame painted that the UI fonts lack.
+    pub(crate) fn frame(&mut self, ctx: &egui::Context) {
+        #[cfg(not(target_arch = "wasm32"))]
+        if let Some(faces) = self.pending.as_ref().and_then(|rx| rx.try_recv().ok()) {
+            self.pending = None;
+            self.install(ctx, &faces);
+        }
+        let missing = self.missing(ctx);
+        if missing.is_empty() {
+            return;
+        }
+        let find = move || {
+            let mut faces: Vec<Arc<FontFace>> = vec![];
+            for c in missing {
+                if let Some(f) = FontDb::global().face_covering(c)
+                    && !faces.iter().any(|x| x.id() == f.id())
+                {
+                    faces.push(f);
+                }
+            }
+            faces
+        };
+        // Native: the installed fonts are read off the UI thread. Characters met meanwhile wait for
+        // the next search (they aren't marked seen until then).
+        #[cfg(not(target_arch = "wasm32"))]
+        {
+            let (tx, rx) = std::sync::mpsc::channel();
+            let repaint = ctx.clone();
+            let spawned = std::thread::Builder::new().name("ui-font-fallback".into()).spawn(move || {
+                // The receiver is gone only when the app is.
+                let _ = tx.send(find());
+                repaint.request_repaint();
+            });
+            if spawned.is_ok() {
+                self.pending = Some(rx);
+            }
+        }
+        // The web has only the loaded fonts to look through: quick, on this thread.
+        #[cfg(target_arch = "wasm32")]
+        self.install(ctx, &find());
+    }
+
+    /// Characters painted this frame that the UI fonts lack and haven't been looked for, now
+    /// marked seen. None while a search is running.
+    fn missing(&mut self, ctx: &egui::Context) -> Vec<char> {
+        #[cfg(not(target_arch = "wasm32"))]
+        if self.pending.is_some() {
+            return vec![];
+        }
+        let mut layers: Vec<LayerId> = ctx.memory(|m| m.layer_ids().collect());
+        if !layers.contains(&LayerId::background()) {
+            layers.push(LayerId::background());
+        }
+        let mut chars: Vec<char> = vec![];
+        let seen = &self.seen;
+        let mut note = |text: &str| {
+            // Most UI text is ASCII, which the UI fonts cover.
+            if !text.is_ascii() {
+                chars.extend(text.chars().filter(|c| !c.is_ascii() && !c.is_whitespace() && !c.is_control() && !seen.contains(c)));
+            }
+        };
+        ctx.graphics(|g| {
+            for l in &layers {
+                for s in g.get(*l).into_iter().flat_map(|list| list.all_entries()) {
+                    painted_text(&s.shape, &mut note);
+                }
+            }
+        });
+        if chars.is_empty() {
+            return chars;
+        }
+        chars.sort_unstable();
+        chars.dedup();
+        let font = FontId::new(13.0, FontFamily::Proportional);
+        let missing: Vec<char> = ctx.fonts_mut(|f| chars.iter().copied().filter(|c| !f.has_glyph(&font, *c)).collect());
+        self.seen.extend(chars);
+        missing
+    }
+
+    /// Add `faces` to every egui family, after the fonts it has.
+    fn install(&mut self, ctx: &egui::Context, faces: &[Arc<FontFace>]) {
+        let families: Vec<FontFamily> = ctx.fonts(|f| f.definitions().families.keys().cloned().collect());
+        for face in faces {
+            let name = format!("{} {} #{}", face.family, face.style, face.face_index());
+            if !self.added.insert(name.clone()) {
+                continue;
+            }
+            // The face's file data, shared with the process-wide font database (which keeps every
+            // face it loads for the session) instead of copied: one handle is leaked per font added.
+            let face: &'static FontFace = Box::leak(Box::new(face.clone()));
+            let data = FontData { index: face.face_index(), ..FontData::from_static(face.file_data()) };
+            let families = families.iter().map(|family| InsertFontFamily { family: family.clone(), priority: FontPriority::Lowest }).collect();
+            ctx.add_font(FontInsert { name, data, families });
+        }
+        if !faces.is_empty() {
+            ctx.request_repaint();
+        }
+    }
+
+    /// Wait for the font search running, if any, and add what it found (tests).
+    #[cfg(test)]
+    pub(crate) fn finish(&mut self, ctx: &egui::Context) {
+        if let Some(faces) = self.pending.take().and_then(|rx| rx.recv().ok()) {
+            self.install(ctx, &faces);
+        }
+    }
+}
+
+/// Call `f` with the text of `shape` and the shapes it holds.
+fn painted_text(shape: &Shape, f: &mut impl FnMut(&str)) {
+    match shape {
+        Shape::Text(t) => f(t.galley.text()),
+        Shape::Vec(v) => v.iter().for_each(|s| painted_text(s, f)),
+        _ => {}
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Run a frame painting `text`, then the fallback search after it.
+    fn frame(ctx: &egui::Context, fonts: &mut UiFonts, text: &str) {
+        let mut out = ctx.run_ui(egui::RawInput::default(), |ui| {
+            ui.label(text);
+            fonts.frame(ui.ctx());
+        });
+        out.textures_delta.clear();
+    }
+
+    fn has_glyph(ctx: &egui::Context, c: char) -> bool {
+        ctx.fonts_mut(|f| f.has_glyph(&FontId::new(13.0, FontFamily::Proportional), c))
+    }
+
+    #[test]
+    fn latin_text_loads_no_fonts() {
+        let ctx = egui::Context::default();
+        crate::theme::install_fonts(&ctx);
+        let mut fonts = UiFonts::default();
+        frame(&ctx, &mut fonts, "Layer 1 — Café");
+        assert!(fonts.pending.is_none() && fonts.added.is_empty());
+    }
+
+    #[test]
+    fn cjk_names_get_an_installed_fallback_font() {
+        let text = "Logo 标志 ロゴ 로고";
+        let ctx = egui::Context::default();
+        crate::theme::install_fonts(&ctx);
+        let mut fonts = UiFonts::default();
+        frame(&ctx, &mut fonts, text);
+        assert!(!has_glyph(&ctx, '标'), "the UI fonts have no CJK");
+        fonts.finish(&ctx);
+        // The fonts arrive with the next frame.
+        frame(&ctx, &mut fonts, text);
+        let installed: Vec<char> = text.chars().filter(|c| !c.is_ascii() && FontDb::global().face_covering(*c).is_some()).collect();
+        if installed.is_empty() {
+            eprintln!("no installed font covers {text}: nothing to check");
+            return;
+        }
+        for c in installed {
+            assert!(has_glyph(&ctx, c), "{c} has a glyph");
+        }
+        // Looked for once: a later frame starts no search.
+        frame(&ctx, &mut fonts, text);
+        assert!(fonts.pending.is_none());
+    }
+}