Take Glow context using Arc. (#1640)

This allows usage with a Glow context that is passed between threads.

eframe/src/epi.rs

@@ -28,7 +28,7 @@ pub struct CreationContext<'s> {
     /// The [`glow::Context`] allows you to initialize OpenGL resources (e.g. shaders) that
     /// you might want to use later from a [`egui::PaintCallback`].
     #[cfg(feature = "glow")]
-    pub gl: Option<std::rc::Rc<glow::Context>>,
+    pub gl: Option<std::sync::Arc<glow::Context>>,
 }
 
 // ----------------------------------------------------------------------------
@@ -334,7 +334,7 @@ pub struct Frame {
     /// A reference to the underlying [`glow`] (OpenGL) context.
     #[cfg(feature = "glow")]
     #[doc(hidden)]
-    pub gl: Option<std::rc::Rc<glow::Context>>,
+    pub gl: Option<std::sync::Arc<glow::Context>>,
 }
 
 impl Frame {
@@ -371,7 +371,7 @@ impl Frame {
     /// To get a [`glow`] context you need to compile with the `glow` feature flag,
     /// and run eframe with the glow backend.
     #[cfg(feature = "glow")]
-    pub fn gl(&self) -> Option<&std::rc::Rc<glow::Context>> {
+    pub fn gl(&self) -> Option<&std::sync::Arc<glow::Context>> {
         self.gl.as_ref()
     }
 

eframe/src/native/epi_integration.rs

@@ -185,7 +185,7 @@ impl EpiIntegration {
         max_texture_side: usize,
         window: &winit::window::Window,
         storage: Option<Box<dyn epi::Storage>>,
-        #[cfg(feature = "glow")] gl: Option<std::rc::Rc<glow::Context>>,
+        #[cfg(feature = "glow")] gl: Option<std::sync::Arc<glow::Context>>,
     ) -> Self {
         let egui_ctx = egui::Context::default();
 

eframe/src/native/run.rs

@@ -51,7 +51,7 @@ pub fn run_glow(
     let window_builder =
         epi_integration::window_builder(native_options, &window_settings).with_title(app_name);
     let (gl_window, gl) = create_display(native_options, window_builder, &event_loop);
-    let gl = std::rc::Rc::new(gl);
+    let gl = std::sync::Arc::new(gl);
 
     let mut painter = egui_glow::Painter::new(gl.clone(), None, "")
         .unwrap_or_else(|error| panic!("some OpenGL error occurred {}\n", error));

eframe/src/web/glow_wrapping.rs

@@ -17,7 +17,7 @@ impl WrappedGlowPainter {
         let canvas = super::canvas_element_or_die(canvas_id);
 
         let (gl, shader_prefix) = init_glow_context_from_canvas(&canvas)?;
-        let gl = std::rc::Rc::new(gl);
+        let gl = std::sync::Arc::new(gl);
 
         let dimension = [canvas.width() as i32, canvas.height() as i32];
         let painter = egui_glow::Painter::new(gl, Some(dimension), shader_prefix)
@@ -32,7 +32,7 @@ impl WrappedGlowPainter {
 }
 
 impl WrappedGlowPainter {
-    pub fn gl(&self) -> &std::rc::Rc<glow::Context> {
+    pub fn gl(&self) -> &std::sync::Arc<glow::Context> {
         self.painter.gl()
     }