Stack Overflow when running metal_triangle example

[drhaynes]

Hi, really excited to see this package. I'm very keen to use Metal from rust.

I'm trying to run the metal_triangle example but am getting a stack overflow.

Steps to reproduce:
$ cargo build
$ cargo run --example metal_triangle

Portion of the stack trace is below:

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   libsystem_kernel.dylib          0x00007fff95823f06 __pthread_kill + 10
1   libsystem_pthread.dylib         0x00007fff9eb624ec pthread_kill + 90
2   libsystem_c.dylib               0x00007fff8dedd6df abort + 129
3   metal_triangle                  0x0000000102cfee1f std::sys::stack_overflow::imp::signal_handler::hff21ef2a2481da88 + 927
4   libsystem_platform.dylib        0x00007fff8e62052a _sigtramp + 26
5   ???                             000000000000000000 0 + 0
6   metal_triangle                  0x0000000102cf9067 _$LT$alloc..raw_vec..RawVec$LT$T$GT$$GT$::double::h7e0e8594a9522e0c + 39
7   metal_triangle                  0x0000000102cf8f29 std::ffi::c_str::CString::from_vec_unchecked::h3a4067cce1afb752 + 41
8   metal_triangle                  0x0000000102cf832e std::ffi::c_str::CString::_new::heb6c4ccd5b4e425d + 158
9   metal_triangle                  0x0000000102cf225c std::ffi::c_str::{{impl}}::new<&str> + 60 (c_str.rs:205)
10  metal_triangle                  0x0000000102cf2bcf objc::runtime::Class::instance_variable::habf51b4c360b69c4 + 47 (runtime.rs:314)
11  metal_triangle                  0x0000000102cc23a2 objc::runtime::{{impl}}::get_ivar<*mut std::os::raw::c_void> + 66 (runtime.rs:443)
12  metal_triangle                  0x0000000102cc2323 metl::extras::window::{{impl}}::set_delegate::draw_in_mtk_view<metal_triangle::main::MyViewDelegate> + 51 (mod.rs:286)
13  com.apple.MetalKit              0x0000000102df2713 -[MTKView draw] + 319
14  metal_triangle                  0x0000000102cc520e objc::message::{{impl}}::invoke<()> + 46 (mod.rs:120)
15  metal_triangle                  0x0000000102cc514b objc::message::send_unverified<objc::runtime::Object,(),()> + 91 (mod.rs:187)
16  metal_triangle                  0x0000000102cc8195 metl::extras::window::View::draw::hac2173034b271621 + 165 (mod.rs:197)
17  metal_triangle                  0x0000000102cc29bd metal_triangle::main::{{impl}}::draw_into_view + 221 (metal_triangle.rs:12)
18  metal_triangle                  0x0000000102cc234f metl::extras::window::{{impl}}::set_delegate::draw_in_mtk_view<metal_triangle::main::MyViewDelegate> + 95 (mod.rs:284)
19  com.apple.MetalKit              0x0000000102df2713 -[MTKView draw] + 319
20  metal_triangle                  0x0000000102cc520e objc::message::{{impl}}::invoke<()> + 46 (mod.rs:120)
21  metal_triangle                  0x0000000102cc514b objc::message::send_unverified<objc::runtime::Object,(),()> + 91 (mod.rs:187)
22  metal_triangle                  0x0000000102cc8195 metl::extras::window::View::draw::hac2173034b271621 + 165 (mod.rs:197)
23  metal_triangle                  0x0000000102cc29bd metal_triangle::main::{{impl}}::draw_into_view + 221 (metal_triangle.rs:12)
24  metal_triangle                  0x0000000102cc234f metl::extras::window::{{impl}}::set_delegate::draw_in_mtk_view<metal_triangle::main::MyViewDelegate> + 95 (mod.rs:284)
25  com.apple.MetalKit              0x0000000102df2713 -[MTKView draw] + 319
26  metal_triangle                  0x0000000102cc520e objc::message::{{impl}}::invoke<()> + 46 (mod.rs:120)
27  metal_triangle                  0x0000000102cc514b objc::message::send_unverified<objc::runtime::Object,(),()> + 91 (mod.rs:187)
28  metal_triangle                  0x0000000102cc8195 metl::extras::window::View::draw::hac2173034b271621 + 165 (mod.rs:197)
29  metal_triangle                  0x0000000102cc29bd metal_triangle::main::{{impl}}::draw_into_view + 221 (metal_triangle.rs:12)
30  metal_triangle                  0x0000000102cc234f metl::extras::window::{{impl}}::set_delegate::draw_in_mtk_view<metal_triangle::main::MyViewDelegate> + 95 (mod.rs:284)
31  com.apple.MetalKit              0x0000000102df2713 -[MTKView draw] + 319

So it seems the culprit is a recursive call to [MTKView draw]. Indeed, commenting out the view.draw call in the delegate and replacing it with a call to window.view.draw() in the main loop makes the crash stop happening. However, there doesn't appear to be any drawing happening, as the window's view is blank, and not showing a red colour as to be expected from the example code.

I have also tried updating the cocoa crate to latest (0.4.4) but this hasn't made a difference.