iris: load application-owned fonts

core/src/primitive/text.rs

@@ -2,18 +2,15 @@ use crate::{Align, GlyphAtlas, GlyphKey, PaintId, PlacedGlyph, RegionAlign, Text
 use parley::{
     Alignment, AlignmentOptions, FontContext, FontFamily, FontFamilyName, FontStyle, FontWeight,
     GenericFamily, Layout, LayoutContext, LineHeight, PositionedLayoutItem, StyleProperty,
-    fontique::Blob,
+    fontique::{Blob, FontInfoOverride},
 };
-use std::ops::Range;
-use std::sync::Arc;
+use std::{collections::HashMap, fmt, ops::Range, sync::Arc};
 use swash::{
     FontRef,
     scale::{Render, ScaleContext, Source, StrikeWith},
     zeno::{Format, Vector},
 };
 
-const NERD_ICONS: &[u8] = include_bytes!("../../assets/fonts/nerd_icons.ttf");
-
 #[derive(Clone, Debug)]
 pub struct FontDiagnostics {
     pub families_found: usize,
@@ -23,13 +20,42 @@ pub struct FontDiagnostics {
     pub bold_resolved: Option<String>,
     pub italic_resolved: Option<String>,
     pub mono_resolved: Option<String>,
-    /// The family the bundled icon font registered under, or `None` if
-    /// registering it failed. Reported rather than assumed: it is the one
-    /// font iris ships, so `None` is a broken build and must not look
-    /// like a device that happens to lack a face.
-    pub icon_family: Option<String>,
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum FontRegistrationError {
+    UnsupportedFamily(Family),
+    AlreadyRegistered(Family),
+    TextAlreadyShaped,
+    InvalidFont(Family),
+}
+
+impl fmt::Display for FontRegistrationError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::UnsupportedFamily(family) => write!(
+                f,
+                "cannot register font data for {family:?}; use Family::Icons or Family::Named"
+            ),
+            Self::AlreadyRegistered(family) => {
+                write!(f, "font data is already registered for {family:?}")
+            }
+            Self::TextAlreadyShaped => write!(
+                f,
+                "cannot register font data after text has been shaped; register application fonts before the first draw"
+            ),
+            Self::InvalidFont(family) => {
+                write!(
+                    f,
+                    "font data registered for {family:?} contains no usable fonts"
+                )
+            }
+        }
+    }
+}
+
+impl std::error::Error for FontRegistrationError {}
+
 pub struct TextData {
     pub font_cx: FontContext,
     pub layout_cx: LayoutContext<PaintId>,
@@ -46,41 +72,28 @@ pub struct TextData {
     /// truth would mean carrying a `Painter` (or output size) into every
     /// input handler for the sake of one field.
     pub density: f32,
-    /// The family name [`NERD_ICONS`] registered under, which is what
-    /// [`Family::Icons`] resolves to. `None` only if registering the
-    /// bundled font failed, which is a broken build rather than a
-    /// platform difference -- said in the startup diagnostics rather than
-    /// silently drawn as tofu.
-    pub icon_family: Option<String>,
+    registered_families: HashMap<Family, String>,
+    next_registered_family: u64,
+    shaping_started: bool,
 }
 
 impl Default for TextData {
     fn default() -> Self {
         let mut font_cx = FontContext::new();
         patch_android_monospace(&mut font_cx);
-        let icon_family = register_icon_font(&mut font_cx);
         Self {
             font_cx,
             layout_cx: LayoutContext::new(),
             scale_cx: ScaleContext::new(),
             atlas: GlyphAtlas::default(),
             density: 1.0,
-            icon_family,
+            registered_families: HashMap::new(),
+            next_registered_family: 0,
+            shaping_started: false,
         }
     }
 }
 
-fn register_icon_font(font_cx: &mut FontContext) -> Option<String> {
-    let blob = Blob::new(Arc::new(NERD_ICONS));
-    let id = font_cx
-        .collection
-        .register_fonts(blob, None)
-        .into_iter()
-        .map(|(id, _)| id)
-        .next()?;
-    font_cx.collection.family_name(id).map(str::to_string)
-}
-
 /// So this reads `fonts.xml` itself (already on-device, already the
 /// authority Compose's own `Typeface.MONOSPACE` resolves through) for the
 /// filename that declaration names, then finds which of fontique's
@@ -154,16 +167,56 @@ fn android_monospace_font_filename() -> Option<String> {
 fn patch_android_monospace(_font_cx: &mut FontContext) {}
 
 impl TextData {
+    pub(crate) fn register_font(
+        &mut self,
+        family: Family,
+        data: impl AsRef<[u8]> + Send + Sync + 'static,
+    ) -> Result<(), FontRegistrationError> {
+        if !matches!(family, Family::Icons | Family::Named(_)) {
+            return Err(FontRegistrationError::UnsupportedFamily(family));
+        }
+        if self.shaping_started {
+            return Err(FontRegistrationError::TextAlreadyShaped);
+        }
+        if self.registered_families.contains_key(&family) {
+            return Err(FontRegistrationError::AlreadyRegistered(family));
+        }
+
+        // Parley selects fonts by family rather than by a face handle. Give
+        // application data a private family name so selecting it cannot find
+        // a system font that happens to carry the same embedded metadata.
+        let private_name = format!("__iris_registered_font_{}__", self.next_registered_family);
+        let fonts = self.font_cx.collection.register_fonts(
+            Blob::new(Arc::new(data)),
+            Some(FontInfoOverride {
+                family_name: Some(&private_name),
+                ..Default::default()
+            }),
+        );
+        if fonts.is_empty() {
+            return Err(FontRegistrationError::InvalidFont(family));
+        }
+        self.next_registered_family += 1;
+        self.registered_families.insert(family, private_name);
+        Ok(())
+    }
+
+    pub(crate) fn is_font_registered(&self, family: &Family) -> bool {
+        self.registered_families.contains_key(family)
+    }
+
     /// Cloned rather than borrowed because the caller needs it while the
-    /// layout builder holds `&mut self` -- a `String` per shaped icon run,
-    /// paid only when the layout is rebuilt.
+    /// layout builder holds `&mut self` -- a `String` per shaped registered
+    /// run, paid only when the layout is rebuilt.
     pub fn resolve_family(&self, family: &Family) -> Family {
+        if let Some(name) = self.registered_families.get(family) {
+            return Family::Named(name.clone());
+        }
         match family {
-            Family::Icons => self
-                .icon_family
-                .clone()
-                .map_or(Family::Icons, Family::Named),
-            other => other.clone(),
+            Family::Icons => panic!(
+                "Family::Icons has no font; register application font data with Ui::register_font before the first draw"
+            ),
+            _ => family.clone(),
         }
     }
 
@@ -236,7 +289,6 @@ impl TextData {
             bold_resolved,
             italic_resolved,
             mono_resolved,
-            icon_family: self.icon_family.clone(),
         }
     }
 
@@ -339,15 +391,13 @@ impl TextData {
 
 /// Which family to ask for. Kept as an owned name rather than parley's
 /// borrowed `FontFamily<'_>` so that a widget can hold one without a lifetime.
-#[derive(Clone, PartialEq)]
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub enum Family {
     SansSerif,
     Serif,
     Monospace,
-    /// The bundled icon font -- see [`crate::icon`] for what is in it.
-    /// Named as an intention rather than as a font name because only
-    /// [`TextData`] knows what the file registered as; it resolves this
-    /// during shaping ([`TextData::resolve_family`]).
+    /// The icon font supplied by the application through
+    /// [`crate::Ui::register_font`].
     Icons,
     Named(String),
 }
@@ -507,6 +557,7 @@ impl TextBuffer {
         width: Option<f32>,
         density: f32,
     ) {
+        data.shaping_started = true;
         if self.shaped.as_ref() == Some(&(attrs.clone(), width, density)) {
             return;
         }
@@ -586,38 +637,24 @@ pub struct RenderedText {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::icon;
 
     #[test]
-    fn every_icon_is_in_the_bundled_font() {
-        let font = FontRef::from_index(NERD_ICONS, 0).expect("the bundled icon font parses");
-        let charmap = font.charmap();
-        for (name, glyph) in [
-            ("OPEN", icon::OPEN),
-            ("CLOSED", icon::CLOSED),
-            ("COLLAPSE", icon::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
-            );
-        }
+    fn invalid_font_data_is_reported() {
+        let mut data = TextData::default();
+        assert_eq!(
+            data.register_font(Family::Icons, b"not a font" as &'static [u8]),
+            Err(FontRegistrationError::InvalidFont(Family::Icons))
+        );
     }
 
     #[test]
-    fn the_icon_family_registers_and_resolves() {
-        let data = TextData::default();
-        let family = data.resolve_family(&Family::Icons);
-        assert!(
-            matches!(family, Family::Named(_)),
-            "the bundled icon font did not register: {:?}",
-            data.icon_family
+    fn registering_after_shaping_is_reported() {
+        let mut data = TextData::default();
+        let mut buffer = TextBuffer::new("ordinary platform text");
+        buffer.shape(&mut data, &TextAttrs::default(), None, 1.0);
+        assert_eq!(
+            data.register_font(Family::Icons, b"not a font" as &'static [u8]),
+            Err(FontRegistrationError::TextAlreadyShaped)
         );
     }
 }