eframe: Introduce NativeOptions::prefer_gl_api to specify the preferred OpenGL API

crates/eframe/src/epi.rs

@@ -25,6 +25,10 @@ use static_assertions::assert_not_impl_any;
 #[cfg(any(feature = "glow", feature = "wgpu"))]
 pub use winit::{event_loop::EventLoopBuilder, window::WindowAttributes};
 
+#[cfg(not(target_arch = "wasm32"))]
+#[cfg(feature = "glow")]
+pub use glutin_winit::ApiPreference as GlApiPreference;
+
 /// Hook into the building of an event loop before it is run
 ///
 /// You can configure any platform specific details required on top of the default configuration
@@ -364,6 +368,13 @@ pub struct NativeOptions {
     ///
     /// Defaults to true.
     pub dithering: bool,
+
+    /// Which OpenGL API to prefer when using [`Renderer::Glow`].
+    ///
+    /// This is only used when the `glow` feature is enabled.
+    /// Default: [`GlApiPreference::FallbackEgl`].
+    #[cfg(feature = "glow")]
+    pub prefer_gl_api: GlApiPreference,
 }
 
 #[cfg(not(target_arch = "wasm32"))]
@@ -424,6 +435,9 @@ impl Default for NativeOptions {
             persistence_path: None,
 
             dithering: true,
+
+            #[cfg(feature = "glow")]
+            prefer_gl_api: GlApiPreference::FallbackEgl,
         }
     }
 }

crates/eframe/src/native/glow_integration.rs

@@ -940,10 +940,7 @@ impl GlutinWindowContext {
 
         // Create GL display. This may probably create a window too on most platforms. Definitely on `MS windows`. Never on Android.
         let display_builder = glutin_winit::DisplayBuilder::new()
-            // we might want to expose this option to users in the future. maybe using an env var or using native_options.
-            //
-            // The justification for FallbackEgl over PreferEgl is at https://github.com/emilk/egui/pull/2526#issuecomment-1400229576 .
-            .with_preference(glutin_winit::ApiPreference::FallbackEgl)
+            .with_preference(native_options.prefer_gl_api) // https://github.com/emilk/egui/issues/2520#issuecomment-1367841150
             .with_window_attributes(Some(egui_winit::create_winit_window_attributes(
                 egui_ctx,
                 event_loop,