You can override the default Egui fonts

Closes https://github.com/emilk/egui/issues/32

CHANGELOG.md

@@ -8,6 +8,7 @@
 * Demo App: Add slider to scale all of Egui
 * Windows are now constrained to the screen
 * Panels: you can now create panels using `SidePanel` and `TopPanel`.
+* You can override the default Egui fonts
 * Fix a bug where some regions would slowly grow for non-integral scales (`pixels_per_point`).
 * You can no longer throw windows
 * `Context::begin_frame()` no longer returns anything.

egui/src/app.rs

@@ -12,6 +12,11 @@ use crate::Context;
 /// Implement this trait to write apps that can be compiled both natively using the [`egui_glium`](https://crates.io/crates/egui_glium) crate,
 /// and deployed as a web site using the [`egui_web`](https://crates.io/crates/egui_web) crate.
 pub trait App {
+    /// Called once before the first frame.
+    /// Allows you to do setup code and to call `ctx.set_fonts()`.
+    /// Optional.
+    fn setup(&mut self, _ctx: &std::sync::Arc<Context>) {}
+
     /// Called each time the UI needs repainting, which may be many times per second.
     /// Put your widgets into a `SidePanel`, `TopPanel`, `CentralPanel`, `Window` or `Area`.
     fn ui(

egui/src/lib.rs

@@ -92,7 +92,10 @@ pub use {
     layout::*,
     math::*,
     memory::Memory,
-    paint::{color, PaintCmd, PaintJobs, Rgba, Srgba, Stroke, TextStyle, Texture, TextureId},
+    paint::{
+        color, FontDefinitions, FontFamily, PaintCmd, PaintJobs, Rgba, Srgba, Stroke, TextStyle,
+        Texture, TextureId,
+    },
     painter::Painter,
     style::Style,
     types::*,

egui/src/paint/fonts.rs

@@ -36,6 +36,11 @@ pub struct FontDefinitions {
     pub pixels_per_point: f32,
 
     pub fonts: BTreeMap<TextStyle, (FontFamily, f32)>,
+
+    /// The TTF data for each font family.
+    /// Egui has built-in-default for these,
+    /// but you can override them if you like.
+    pub ttf_data: BTreeMap<FontFamily, &'static [u8]>,
 }
 
 impl Default for FontDefinitions {
@@ -51,11 +56,20 @@ impl FontDefinitions {
         fonts.insert(TextStyle::Body, (FontFamily::VariableWidth, 14.0));
         fonts.insert(TextStyle::Button, (FontFamily::VariableWidth, 16.0));
         fonts.insert(TextStyle::Heading, (FontFamily::VariableWidth, 24.0));
-        fonts.insert(TextStyle::Monospace, (FontFamily::Monospace, 13.0));
+        fonts.insert(TextStyle::Monospace, (FontFamily::Monospace, 13.0)); // 13 for `ProggyClean`
+
+        // TODO: figure out a way to make the WASM smaller despite including a font. Zip it?
+        let monospace_typeface_data = include_bytes!("../../fonts/ProggyClean.ttf"); // Use 13 for this. NOTHING ELSE.
+        let variable_typeface_data = include_bytes!("../../fonts/Comfortaa-Regular.ttf"); // Funny, hard to read
+
+        let mut ttf_data: BTreeMap<FontFamily, &'static [u8]> = BTreeMap::new();
+        ttf_data.insert(FontFamily::Monospace, monospace_typeface_data);
+        ttf_data.insert(FontFamily::VariableWidth, variable_typeface_data);
 
         Self {
             pixels_per_point,
             fonts,
+            ttf_data,
         }
     }
 }
@@ -98,32 +112,21 @@ impl Fonts {
 
         let atlas = Arc::new(Mutex::new(atlas));
 
-        // TODO: figure out a way to make the WASM smaller despite including a font. Zip it?
-        let monospace_typeface_data = include_bytes!("../../fonts/ProggyClean.ttf"); // Use 13 for this. NOTHING ELSE.
-
-        // let monospace_typeface_data = include_bytes!("../../fonts/Roboto-Regular.ttf");
-
-        let variable_typeface_data = include_bytes!("../../fonts/Comfortaa-Regular.ttf"); // Funny, hard to read
-
-        // let variable_typeface_data = include_bytes!("../../fonts/DejaVuSans.ttf"); // Basic, boring, takes up more space
-
         self.definitions = definitions.clone();
         let FontDefinitions {
             pixels_per_point,
             fonts,
+            ttf_data,
         } = definitions;
         self.fonts = fonts
             .into_iter()
             .map(|(text_style, (family, size))| {
-                let typeface_data: &[u8] = match family {
-                    FontFamily::Monospace => monospace_typeface_data,
-                    FontFamily::VariableWidth => variable_typeface_data,
-                };
+                let typeface_data = ttf_data
+                    .get(&family)
+                    .unwrap_or_else(|| panic!("Missing TTF data for {:?}", family));
+                let font = Font::new(atlas.clone(), typeface_data, size, pixels_per_point);
 
-                (
-                    text_style,
-                    Font::new(atlas.clone(), typeface_data, size, pixels_per_point),
-                )
+                (text_style, font)
             })
             .collect();
 

egui/src/paint/mod.rs

@@ -13,7 +13,7 @@ mod texture_atlas;
 pub use {
     color::{Rgba, Srgba},
     command::{PaintCmd, Stroke},
-    fonts::{FontDefinitions, Fonts, TextStyle},
+    fonts::{FontDefinitions, FontFamily, Fonts, TextStyle},
     stats::PaintStats,
     tessellator::{PaintJob, PaintJobs, PaintOptions, TextureId, Triangles, Vertex, WHITE_UV},
     texture_atlas::Texture,

egui_glium/src/backend.rs

@@ -57,6 +57,7 @@ pub fn run(
 
     let mut ctx = egui::Context::new();
     *ctx.memory() = egui::app::get_value(storage.as_ref(), EGUI_MEMORY_KEY).unwrap_or_default();
+    app.setup(&ctx);
 
     let mut raw_input = egui::RawInput {
         pixels_per_point: Some(native_pixels_per_point(&display)),

egui_web/src/backend.rs

@@ -132,7 +132,8 @@ pub struct AppRunner {
 }
 
 impl AppRunner {
-    pub fn new(web_backend: WebBackend, app: Box<dyn App>) -> Result<Self, JsValue> {
+    pub fn new(web_backend: WebBackend, mut app: Box<dyn App>) -> Result<Self, JsValue> {
+        app.setup(&web_backend.ctx);
         Ok(Self {
             pixels_per_point: native_pixels_per_point(),
             web_backend,