Encounter Self-referential type when using winit(>= 0.30) Window and wgpu's Surface

[ifsheldon]

Hi all! I am maintaining a Direct Volume Rendering(DVR) app which depends on wgpu and winit. When I tried to update my app to use winit >= 0.30, I was stuck in the problem of self reference. Do you have any ideas to resolve this?

A bit of background:

• Recently, winit decided to make their event handling APIs to be trait-based. In its documentation, the example needs to store a window: Option<Windows> for resume method and requesting redraws.
  https://github.com/rust-windowing/winit/blob/73c01fff96266a6a7d9159e9bd26acc00df0bbc9/src/lib.rs#L79
• A Surface has a reference to a window, in the case of my app, to winit::Window
  https://docs.rs/wgpu/22.0.0/src/wgpu/lib.rs.html#584-606

In my case, I need these in my App states:

• window: winit::Window to request redraw and get its size if the window's scaling factor gets changed.
• surface: wgpu: Surface<'window> to use Surface::get_current_texture before doing the actual rendering.

I can use ouroboros to create self-referential types but I don't know what will happen if a Window got replaced by another during winit::application::ApplicationHandler::resumed.

So I have actually 3 questions, which may be issues when using wgpu and winit in combo:

1. How can I store winit::Window and wgpu::Surface<'window> together?
2. Is there a potential dangling pointer problem when a winit::Window gets replaced during winit::application::ApplicationHandler::resumed?
3. How can we avoid this dangling pointer problem if it may exist?

Further references:

• My code is opensourced on https://github.com/nanovis/Wenderer
  • the main branch works with wgpu 22.0.0 and winit 0.29
  • the winit0.30 branch fails compilation due to self reference.....

[cwfitzgerald]

1. You can put the window in an Arc, then hand the surface a clone of the Arc. The lifetime will be static.
2. Because of the Arc, everything should work fine

[ifsheldon]

Awesome! It takes a bit refactoring but it works! Thanks a lot!