iris: load application-owned fonts

app/src/ui/icon.rs

@@ -0,0 +1,30 @@
+pub const OPEN: &str = "\u{F035D}";
+
+pub const CLOSED: &str = "\u{F035F}";
+
+pub const COLLAPSE: &str = "\u{F0360}";
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use swash::FontRef;
+
+    #[test]
+    fn every_icon_is_in_the_application_font() {
+        let font = FontRef::from_index(super::super::ICON_FONT, 0)
+            .expect("the application icon font parses");
+        let charmap = font.charmap();
+        for (name, glyph) in [("OPEN", OPEN), ("CLOSED", CLOSED), ("COLLAPSE", COLLAPSE)] {
+            let mut chars = glyph.chars();
+            let ch = chars.next().expect("an icon is one character");
+            assert!(chars.next().is_none(), "{name} is more than one character");
+            assert_ne!(
+                charmap.map(ch),
+                0,
+                "{name} (U+{:04X}) is not in nerd_icons.ttf -- add it to \
+                 build-icon-font.sh's GLYPHS and rerun the script",
+                ch as u32
+            );
+        }
+    }
+}

app/src/ui/mod.rs

@@ -2,6 +2,7 @@ pub mod composer;
 // Keep the 1.9 MB fixture out of ordinary APKs.
 #[cfg(feature = "fixture")]
 pub mod fixture;
+mod icon;
 pub mod markdown;
 pub mod row;
 pub(crate) mod tap;
@@ -13,6 +14,16 @@ use iris::prelude::*;
 use std::{mem, rc::Rc};
 use theme::Theme;
 
+const ICON_FONT: &[u8] = include_bytes!("../../assets/fonts/nerd_icons.ttf");
+
+pub(crate) fn register_fonts(ui: &mut Ui) {
+    if ui.is_font_registered(&Family::Icons) {
+        return;
+    }
+    ui.register_font(Family::Icons, ICON_FONT)
+        .expect("the ai-app icon font must register before text is drawn");
+}
+
 pub struct TranscriptScreen {
     /// The transcript's own `LazySpan` -- the layout *and* the scroll
     /// position, since a lazy span owns a `ScrollController` of its own
@@ -241,6 +252,7 @@ pub fn build_tree<Rsc: HasEvents>(
 where
     Rsc::State: FocusHost + OpenUrl,
 {
+    register_fonts(rsc.ui_mut());
     let theme = Rc::new(Theme::new(&mut rsc.ui_mut().paints));
     let list = LazySpan::new(Dir::DOWN, Pin::End).add(rsc);
     list.controller(

app/src/ui/tool.rs

@@ -1,6 +1,7 @@
 use crate::client::text_cap::{VERBATIM_BYTES, VERBATIM_LINES, cut, show_all_label};
 use crate::client::tool_summary::{ToolInput, parse_tool_input};
 use crate::client::transcript_fold::{ToolState, TranscriptItem};
+use crate::ui::icon;
 use crate::ui::markdown::highlight_into;
 use crate::ui::tap::{hold_edge, on_tap};
 use crate::ui::theme::Theme;