vulkano/TROUBLES.md

Troubles encountered with Rust during the making of this library

• Lack of plugins means that you have to use a build script to compile your shaders instead of inlining them directly where they are used.

• No way to create dynamic-sized arrays on the stack. A lot of Vulkan functions require passing an array of small elements (small structs or integers). Building such an array with a Vec can be expensive, especially when most of the time the array only contains a single element.

• Having a trait that defines which types can be put inside buffers is very annoying, as users have to implement it for every single struct they create. The best solution would be to use impl BufferContent for ... {}, but this syntax is still unstable.

• No way to create a *mut T pointer from a *mut c_void and a size when T is unsized. This had to be implemented in a custom trait.

• Can't cast an ImageResource into a Resource even though the former depends on the latter.

• This library was designed with specialization in mind. There are several is_compatible trait methods that perform deep comparisons between layouts. With specialization available, these methods could be specialized as true for layouts that are known to always be compatible.

• https://github.com/rust-lang/rust/issues/29328

• Some trait implementations have an associated type that looks like type T = (Arc<Foo>, Arc<Bar>);. HKTs would allow this parameter to take references to the Arcs instead, and avoid having to clone them. This problem could by bypassed by making the code more ugly, but it's not worth it just to avoid cloning some Arcs.

• Visibility rules mean that you can't write struct Error; pub mod foo { pub struct Foo; impl From<Error> for Foo { ... } }. Rustc complains that Error is private an exported in Foo's signature, even though that's in the author's opinion a totally legitimate usage.

• This repository contains the vulkano-shaders library, which generates Rust code that uses the vulkano library. If the API of vulkano gets a breaking change, there is no way to enforce or to check the fact that the user uses a correct combination of versions for vulkano-shaders and vulkano.

• No way to set the alignment of a struct member, or to force the size of a struct to be a multiple of a certain size.

• The fact that is legal to implement Deref and return a different object every time means that it is dangerous to interface with a Foo through a P where P: Deref<Foo>. That P could return several different Foos, and the implementation can't rely on the fact that the object will be the same every time.