Add glow::Context to epi::App::setup

eframe/examples/custom_font.rs

@@ -22,6 +22,7 @@ impl epi::App for MyApp {
         ctx: &egui::Context,
         _frame: &epi::Frame,
         _storage: Option<&dyn epi::Storage>,
+        _gl: &std::rc::Rc<epi::glow::Context>,
     ) {
         // Start with the default fonts (we will be adding to them rather than replacing them).
         let mut fonts = egui::FontDefinitions::default();

egui-winit/Cargo.toml

@@ -24,6 +24,12 @@ default = ["clipboard", "dark-light", "links"]
 # if disabled a clipboard will be simulated so you can still copy/paste within the egui app.
 clipboard = ["copypasta"]
 
+# implement bytemuck on most types.
+convert_bytemuck = ["egui/convert_bytemuck"]
+
+# Only for `egui_glow` - the official eframe/epi backend.
+epi_backend = ["epi", "glow"]
+
 # enable opening links in a browser when an egui hyperlink is clicked.
 links = ["webbrowser"]
 
@@ -36,9 +42,6 @@ persistence = [
 ] # can't add epi/persistence here because of https://github.com/rust-lang/cargo/issues/8832
 serialize = ["egui/serialize", "serde"]
 
-# implement bytemuck on most types.
-convert_bytemuck = ["egui/convert_bytemuck"]
-
 
 [dependencies]
 egui = { version = "0.17.0", path = "../egui", default-features = false, features = [
@@ -53,6 +56,7 @@ epi = { version = "0.17.0", path = "../epi", optional = true }
 
 copypasta = { version = "0.7", optional = true }
 dark-light = { version = "0.2.1", optional = true }                 # detect dark mode system preference
+glow = { version = "0.11", optional = true }
 serde = { version = "1.0", optional = true, features = ["derive"] }
 webbrowser = { version = "0.6", optional = true }
 

egui-winit/src/epi.rs

@@ -232,6 +232,7 @@ impl EpiIntegration {
         integration_name: &'static str,
         max_texture_side: usize,
         window: &winit::window::Window,
+        gl: &std::rc::Rc<glow::Context>,
         repaint_signal: std::sync::Arc<dyn epi::backend::RepaintSignal>,
         persistence: crate::epi::Persistence,
         app: Box<dyn epi::App>,
@@ -271,17 +272,17 @@ impl EpiIntegration {
             can_drag_window: false,
         };
 
-        slf.setup(window);
+        slf.setup(window, gl);
         if slf.app.warm_up_enabled() {
             slf.warm_up(window);
         }
 
         slf
     }
 
-    fn setup(&mut self, window: &winit::window::Window) {
+    fn setup(&mut self, window: &winit::window::Window, gl: &std::rc::Rc<glow::Context>) {
         self.app
-            .setup(&self.egui_ctx, &self.frame, self.persistence.storage());
+            .setup(&self.egui_ctx, &self.frame, self.persistence.storage(), gl);
         let app_output = self.frame.take_app_output();
 
         if app_output.quit {

egui_demo_lib/src/apps/demo/app.rs

@@ -19,6 +19,7 @@ impl epi::App for DemoApp {
         _ctx: &egui::Context,
         _frame: &epi::Frame,
         _storage: Option<&dyn epi::Storage>,
+        _gl: &std::rc::Rc<epi::glow::Context>,
     ) {
         #[cfg(feature = "persistence")]
         if let Some(storage) = _storage {

egui_demo_lib/src/wrap_app.rs

@@ -47,6 +47,7 @@ impl epi::App for WrapApp {
         _ctx: &egui::Context,
         _frame: &epi::Frame,
         _storage: Option<&dyn epi::Storage>,
+        _gl: &std::rc::Rc<epi::glow::Context>,
     ) {
         #[cfg(feature = "persistence")]
         if let Some(storage) = _storage {

egui_glow/Cargo.toml

@@ -69,7 +69,7 @@ tracing = "0.1"
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 egui-winit = { version = "0.17.0", path = "../egui-winit", optional = true, default-features = false, features = [
   "dark-light",
-  "epi",
+  "epi_backend",
 ] }
 glutin = { version = "0.28.0", optional = true }
 

egui_glow/src/epi_backend.rs

@@ -66,6 +66,7 @@ pub fn run(app: Box<dyn epi::App>, native_options: &epi::NativeOptions) -> ! {
         "egui_glow",
         painter.max_texture_side(),
         gl_window.window(),
+        &gl,
         repaint_signal,
         persistence,
         app,

egui_web/src/backend.rs

@@ -193,11 +193,10 @@ impl AppRunner {
 
         runner.input.raw.max_texture_side = Some(runner.painter.max_texture_side());
 
-        {
-            runner
-                .app
-                .setup(&runner.egui_ctx, &runner.frame, Some(&runner.storage));
-        }
+        let gl = runner.painter.painter.gl();
+        runner
+            .app
+            .setup(&runner.egui_ctx, &runner.frame, Some(&runner.storage), gl);
 
         Ok(runner)
     }

epi/Cargo.toml

@@ -31,6 +31,7 @@ persistence = ["ron", "serde", "egui/persistence"]
 egui = { version = "0.17.0", path = "../egui", default-features = false, features = [
   "single_threaded",
 ] }
+glow = "0.11"
 tracing = "0.1"
 
 directories-next = { version = "2", optional = true }

epi/src/lib.rs

@@ -94,6 +94,7 @@
 pub mod file_storage;
 
 pub use egui; // Re-export for user convenience
+pub use glow; // Re-export for user convenience
 
 use std::sync::{Arc, Mutex};
 
@@ -112,13 +113,23 @@ pub trait App {
     /// or call [`Frame::request_repaint`] at any time (e.g. from another thread).
     fn update(&mut self, ctx: &egui::Context, frame: &Frame);
 
-    /// Called once before the first frame.
+    /// Called exactly once at startup, before any call to [`Self::update`].
     ///
     /// Allows you to do setup code, e.g to call [`egui::Context::set_fonts`],
     /// [`egui::Context::set_visuals`] etc.
     ///
-    /// Also allows you to restore state, if there is a storage (required the "persistence" feature).
-    fn setup(&mut self, _ctx: &egui::Context, _frame: &Frame, _storage: Option<&dyn Storage>) {}
+    /// Also allows you to restore state, if there is a storage (requires the "persistence" feature).
+    ///
+    /// The [`glow::Context`] allows you to initialize OpenGL resources (e.g. shaders) that
+    /// you might want to use later from a [`egui::PaintCallback`].
+    fn setup(
+        &mut self,
+        _ctx: &egui::Context,
+        _frame: &Frame,
+        _storage: Option<&dyn Storage>,
+        _gl: &std::rc::Rc<glow::Context>,
+    ) {
+    }
 
     /// Called on shutdown, and perhaps at regular intervals. Allows you to save state.
     ///