RepaintSignal now implements Sync so it can be sent to another thread

Fixes https://github.com/emilk/egui/issues/82

CHANGELOG.md

@@ -9,6 +9,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## Unreleased
 
+### Fixed 🐛
+
+* `RepaintSignal` now implements `Sync` so it can be sent to a background thread.
+
+
 ## 0.6.0 - 2020-12-26
 
 ### Added ⭐

egui/src/app.rs

@@ -55,7 +55,7 @@ pub struct IntegrationContext<'a> {
     pub tex_allocator: Option<&'a mut dyn TextureAllocator>,
     /// Where the app can issue commands back to the integration.
     pub output: AppOutput,
-    /// If you need to request a repaint from another thread, clone this and give to that other thread
+    /// If you need to request a repaint from another thread, clone this and send it to that other thread.
     pub repaint_signal: std::sync::Arc<dyn RepaintSignal>,
 }
 
@@ -113,7 +113,7 @@ pub trait TextureAllocator {
     fn free(&mut self, id: crate::TextureId);
 }
 
-pub trait RepaintSignal: Send {
+pub trait RepaintSignal: Send + Sync {
     /// This signals the Egui integration that a repaint is required.
     /// This is meant to be called when a background process finishes in an async context and/or background thread.
     fn request_repaint(&self);

egui_glium/src/backend.rs

@@ -31,11 +31,13 @@ impl egui::app::TextureAllocator for Painter {
 
 struct RequestRepaintEvent;
 
-struct GliumRepaintSignal(glutin::event_loop::EventLoopProxy<RequestRepaintEvent>);
+struct GliumRepaintSignal(
+    std::sync::Mutex<glutin::event_loop::EventLoopProxy<RequestRepaintEvent>>,
+);
 
 impl egui::app::RepaintSignal for GliumRepaintSignal {
     fn request_repaint(&self) {
-        self.0.send_event(RequestRepaintEvent).ok();
+        self.0.lock().unwrap().send_event(RequestRepaintEvent).ok();
     }
 }
 
@@ -105,7 +107,9 @@ pub fn run(mut app: Box<dyn App>) -> ! {
     let event_loop = glutin::event_loop::EventLoop::with_user_event();
     let display = create_display(app.name(), window_settings, app.is_resizable(), &event_loop);
 
-    let repaint_signal = std::sync::Arc::new(GliumRepaintSignal(event_loop.create_proxy()));
+    let repaint_signal = std::sync::Arc::new(GliumRepaintSignal(std::sync::Mutex::new(
+        event_loop.create_proxy(),
+    )));
 
     let mut ctx = egui::CtxRef::default();
     *ctx.memory() = storage