Take Glow context using Arc. (#1640)

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

egui_glow/src/painter.rs

@@ -1,6 +1,6 @@
 #![allow(unsafe_code)]
 
-use std::{collections::HashMap, rc::Rc};
+use std::{collections::HashMap, sync::Arc};
 
 use egui::{
     emath::Rect,
@@ -42,7 +42,7 @@ impl TextureFilterExt for TextureFilter {
 /// This struct must be destroyed with [`Painter::destroy`] before dropping, to ensure OpenGL
 /// objects have been properly deleted and are not leaked.
 pub struct Painter {
-    gl: Rc<glow::Context>,
+    gl: Arc<glow::Context>,
 
     max_texture_side: usize,
 
@@ -82,7 +82,7 @@ impl Painter {
     /// * failed to create postprocess on webgl with `sRGB` support
     /// * failed to create buffer
     pub fn new(
-        gl: Rc<glow::Context>,
+        gl: Arc<glow::Context>,
         pp_fb_extent: Option<[i32; 2]>,
         shader_prefix: &str,
     ) -> Result<Painter, String> {
@@ -219,7 +219,7 @@ impl Painter {
     }
 
     /// Access the shared glow context.
-    pub fn gl(&self) -> &std::rc::Rc<glow::Context> {
+    pub fn gl(&self) -> &Arc<glow::Context> {
         &self.gl
     }
 

egui_glow/src/post_process.rs

@@ -7,7 +7,7 @@ use glow::HasContext as _;
 /// Uses a framebuffer to render everything in linear color space and convert it back to `sRGB`
 /// in a separate "post processing" step
 pub(crate) struct PostProcess {
-    gl: std::rc::Rc<glow::Context>,
+    gl: std::sync::Arc<glow::Context>,
     pos_buffer: glow::Buffer,
     index_buffer: glow::Buffer,
     vao: crate::vao::VertexArrayObject,
@@ -21,7 +21,7 @@ pub(crate) struct PostProcess {
 
 impl PostProcess {
     pub(crate) unsafe fn new(
-        gl: std::rc::Rc<glow::Context>,
+        gl: std::sync::Arc<glow::Context>,
         shader_prefix: &str,
         is_webgl_1: bool,
         [width, height]: [i32; 2],

egui_glow/src/winit.rs

@@ -12,7 +12,7 @@ pub struct EguiGlow {
 }
 
 impl EguiGlow {
-    pub fn new(window: &winit::window::Window, gl: std::rc::Rc<glow::Context>) -> Self {
+    pub fn new(window: &winit::window::Window, gl: std::sync::Arc<glow::Context>) -> Self {
         let painter = crate::Painter::new(gl, None, "")
             .map_err(|error| {
                 tracing::error!("error occurred in initializing painter:\n{}", error);