conrod_glium fails backend.is_current() on MacOS

[alberdingk-thijm]

I get the following panic when trying to run some code that calls glium::Display::new(window, context, &events_loop) on MacOS.

thread 'main' panicked at 'assertion failed: backend.is_current()', /Users/tim/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/glium-0.23.0/src/context/mod.rs:647:17
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
             at src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at src/libstd/sys_common/backtrace.rs:59
             at src/libstd/panicking.rs:211
   3: std::panicking::default_hook
             at src/libstd/panicking.rs:227
   4: <std::panicking::begin_panic::PanicPayload<A> as core::panic::BoxMeUp>::get
             at src/libstd/panicking.rs:491
   5: <alloc::collections::CollectionAllocErr as core::convert::From<core::alloc::AllocErr>>::from
             at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/panicking.rs:425
   6: glium::context::Context::get_version
             at /Users/tim/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/glium-0.23.0/src/context/mod.rs:647
   7: glium::context::default_debug_callback::{{closure}}
             at /Users/tim/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/glium-0.23.0/src/context/mod.rs:951
   8: glium::texture::buffer_texture::BufferTextureRef::get_texture_type
             at /Users/tim/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/glium-0.23.0/src/context/mod.rs:217
   9: glium::backend::glutin::Display::new_inner
             at /Users/tim/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/glium-0.23.0/src/backend/glutin/mod.rs:115
  10: <&'b str as core::str::pattern::Pattern<'a>>::into_searcher
             at /Users/tim/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/glium-0.23.0/src/backend/glutin/mod.rs:94
  11: <&'b str as core::str::pattern::Pattern<'a>>::into_searcher
             at /Users/tim/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/glium-0.23.0/src/backend/glutin/mod.rs:79
  12: <&'b str as core::str::pattern::Pattern<'a>>::into_searcher
             at /Users/tim/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/glium-0.23.0/src/backend/glutin/mod.rs:71
  13: merx_conrod::start
             at frontends/conrod/src/main.rs:76
  14: merx_conrod::main
             at frontends/conrod/src/main.rs:232
  15: std::rt::lang_start::{{closure}}
             at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/rt.rs:74
  16: std::panicking::try::do_call
             at src/libstd/rt.rs:59
             at src/libstd/panicking.rs:310
  17: panic_unwind::dwarf::eh::read_encoded_pointer
             at src/libpanic_unwind/lib.rs:102
  18: std::panicking::update_count_then_panic
             at src/libstd/panicking.rs:289
             at src/libstd/panic.rs:398
             at src/libstd/rt.rs:58
  19: std::rt::lang_start
             at /rustc/9fda7c2237db910e41d6a712e9a2139b352e558b/src/libstd/rt.rs:74
  20: merx_conrod::main

This appears to be related to this issue in glium: #1721, where the solution requires changing to glium = "0.24".
Unfortunately, doing so here causes version mismatch errors, as conrod_glium uses glium = "0.23", which is what I currently have in my Cargo.toml.
Changing to 0.24 leads to a series of bounds and types errors:

error[E0277]: the trait bound `glium::backend::glutin::Display: glium::backend::Facade` is not satisfied
  --> frontends/conrod/src/main.rs:88:24
   |
88 |     let mut renderer = Renderer::new(&display.0)?;
   |                        ^^^^^^^^^^^^^ the trait `glium::backend::Facade` is not implemented for `glium::backend::glutin::Display`
   |
   = note: required by `conrod_glium::Renderer::new`

error[E0308]: mismatched types
   --> frontends/conrod/src/main.rs:186:57
    |
186 |             if let Some(event) = support::convert_event(event.clone(), &display) {
    |                                                         ^^^^^^^^^^^^^ expected enum `winit::events::Event`, found a different enum `winit::events::Event`
    |
    = note: expected type `winit::events::Event` (enum `winit::events::Event`)
               found type `winit::events::Event` (enum `winit::events::Event`)
note: Perhaps two different versions of crate `winit` are being used?
   --> frontends/conrod/src/main.rs:186:57
    |
186 |             if let Some(event) = support::convert_event(event.clone(), &display) {
    |                                                         ^^^^^^^^^^^^^

error[E0308]: mismatched types
   --> frontends/conrod/src/main.rs:162:23
    |
162 |         renderer.fill(display, primitives.walk(), &image_map);
    |                       ^^^^^^^ expected struct `glium::backend::glutin::Display`, found a different struct `glium::backend::glutin::Display`
    |
    = note: expected type `&glium::backend::glutin::Display` (struct `glium::backend::glutin::Display`)
               found type `&glium::backend::glutin::Display` (struct `glium::backend::glutin::Display`)
note: Perhaps two different versions of crate `glium` are being used?
   --> frontends/conrod/src/main.rs:162:23
    |
162 |         renderer.fill(display, primitives.walk(), &image_map);
    |                       ^^^^^^^

error[E0271]: type mismatch resolving `<glium::texture::texture2d::Texture2d as std::ops::Deref>::Target == glium::texture::any::TextureAny`
   --> frontends/conrod/src/main.rs:162:18
    |
162 |         renderer.fill(display, primitives.walk(), &image_map);
    |                  ^^^^ expected struct `glium::texture::any::TextureAny`, found a different struct `glium::texture::any::TextureAny`
    |
    = note: expected type `glium::texture::any::TextureAny` (struct `glium::texture::any::TextureAny`)
               found type `glium::texture::any::TextureAny` (struct `glium::texture::any::TextureAny`)
note: Perhaps two different versions of crate `glium` are being used?
   --> frontends/conrod/src/main.rs:162:18
    |
162 |         renderer.fill(display, primitives.walk(), &image_map);
    |                  ^^^^
    = note: required because of the requirements on the impl of `conrod_glium::TextureDimensions` for `glium::texture::texture2d::Texture2d`

error[E0277]: the trait bound `glium::backend::glutin::Display: glium::backend::Facade` is not satisfied
   --> frontends/conrod/src/main.rs:165:18
    |
165 |         renderer.draw(display, &mut target, &image_map).unwrap();
    |                  ^^^^ the trait `glium::backend::Facade` is not implemented for `glium::backend::glutin::Display`

error[E0277]: the trait bound `glium::Frame: glium::Surface` is not satisfied
   --> frontends/conrod/src/main.rs:165:18
    |
165 |         renderer.draw(display, &mut target, &image_map).unwrap();
    |                  ^^^^ the trait `glium::Surface` is not implemented for `glium::Frame`

error[E0277]: the trait bound `for<'a> glium::uniforms::sampler::Sampler<'a, glium::texture::texture2d::Texture2d>: glium::uniforms::AsUniformValue` is not satisfied
   --> frontends/conrod/src/main.rs:165:18
    |
165 |         renderer.draw(display, &mut target, &image_map).unwrap();
    |                  ^^^^ the trait `for<'a> glium::uniforms::AsUniformValue` is not implemented for `glium::uniforms::sampler::Sampler<'a, glium::texture::texture2d::Texture2d>`
    |
    = help: the following implementations were found:
              <glium::uniforms::sampler::Sampler<'a, glium::texture::compressed_srgb_texture1d_array::CompressedSrgbTexture1dArray> as glium::uniforms::AsUniformValue>
              <glium::uniforms::sampler::Sampler<'a, glium::texture::compressed_srgb_texture3d::CompressedSrgbTexture3d> as glium::uniforms::AsUniformValue>
              <glium::uniforms::sampler::Sampler<'a, glium::texture::depth_texture1d::DepthTexture1d> as glium::uniforms::AsUniformValue>
              <glium::uniforms::sampler::Sampler<'a, glium::texture::depth_texture2d_multisample_array::DepthTexture2dMultisampleArray> as glium::uniforms::AsUniformValue>
            and 55 others

error: aborting due to 7 previous errors

Some errors occurred: E0271, E0277, E0308.
For more information about an error, try `rustc --explain E0271`.
error: Could not compile `merx_conrod`.

To learn more, run the command again with --verbose.

[alberdingk-thijm]

For what it's worth, glutin 0.20 also uses winit 0.19, so that would also need to be updated.

[bugeats]

It appears there's been lot of changes in glium 0.24, including a fix for this issue. The conrod_glium backend hasn't been updated in six months (as of this writing).