Wgpu: Is there any chance that I can choose to enable what backend will be compiled into the binary?

[xhebox]

Is your feature request related to a problem? Please describe.
I've tried gfx-hal, and that is good library. But wgpu is much easier to use than gfx. I prefer wgpu and I know clearly I only want to use vulkan. Despite what backend flags I passed to init the instance, gl backend is also compiled.

Describe the solution you'd like
Some features passed from wgpu-rs to wgpu, so that I can choose what I want to use.

Describe alternatives you've considered
None

Additional context
None

[kvark]

Are you concerned about the code size for the GL backend that becomes a part of the binary? It would be interesting to make a test, say with your application, by compile-time disabling GL and seeing how it affected the size. This would be done by checking out wgpu and adding a patch section to your Cargo toml.

[xhebox]

Yes, it is around 0.7MB using cargo-bloat. Another big library is spirv_cross. This is what I got under windows, after removing gl and dx11:

cargo bloat --release --crates

 File  .text     Size Crate
23.3%  34.3%   1.7MiB spirv_cross
22.2%  32.6%   1.6MiB std
11.8%  17.3% 877.4KiB [Unknown]
10.7%  15.7% 795.2KiB wgpu_core
 0.1%   0.1%   4.4KiB wepoll_sys
68.0% 100.0%   4.9MiB .text section size, the file size is 7.3MiB

I'll get the output under linux later.

[kvark]

SPIRV-Cross has just become an optional dependency in #1220, so maybe this is fine now?
Note that there is going to be a bit of a delay before wgpu-rs can consider it to be optional.

[xhebox]

OK, I remembered it wrong... Basically the largest one is spirv_cross. Of course, this result is with lto = true. This is the result under linux:

15.3%  21.2% 758.8KiB wgpu
13.7%  19.0% 678.7KiB spirv_cross
 9.0%  12.5% 446.7KiB std
 8.1%  11.2% 401.0KiB wgpu_core
 7.0%   9.7% 346.9KiB naga
 3.2%   4.4% 156.9KiB [Unknown]
 2.8%   3.9% 138.8KiB wgpu_lut
 2.5%   3.4% 122.4KiB gfx_backend_gl
 1.8%   2.6%  91.3KiB inplace_it
 1.7%   2.3%  83.4KiB hashbrown
 1.1%   1.5%  52.8KiB gfx_backend_vulkan
 0.8%   1.2%  41.7KiB gpu_descriptor
 0.7%   1.0%  35.2KiB ash
 0.5%   0.7%  24.7KiB spirv_headers
 0.4%   0.6%  21.1KiB async_io
 0.4%   0.6%  20.6KiB gfx_hal
 0.4%   0.5%  18.0KiB async_global_executor
 0.3%   0.4%  14.8KiB glow
 0.3%   0.4%  14.1KiB parking_lot
 0.2%   0.3%  11.0KiB miniz_oxide
 1.4%   1.9%  68.9KiB And 26 more crates. Use -n N to show more.

This what I got without lto:

14.7%  23.8% 972.8KiB wgpu
10.3%  16.7% 680.9KiB spirv_cross
 6.1%   9.9% 403.6KiB naga
 5.4%   8.7% 357.4KiB std
 5.4%   8.7% 355.3KiB wgpu_core
 4.2%   6.7% 275.7KiB inplace_it
 2.8%   4.6% 186.7KiB wgpu_lut
 2.4%   3.9% 157.5KiB gfx_backend_gl
 2.1%   3.5% 141.0KiB [Unknown]
 1.3%   2.1%  85.7KiB hashbrown
 1.0%   1.6%  66.3KiB gfx_backend_vulkan
 0.8%   1.3%  54.1KiB ash
 0.5%   0.8%  32.1KiB async_global_executor
 0.5%   0.8%  31.3KiB glow
 0.4%   0.7%  29.8KiB async_io
 0.3%   0.6%  23.2KiB gpu_descriptor
 0.3%   0.5%  20.9KiB gpu_alloc
 0.3%   0.5%  20.9KiB gfx_hal
 0.2%   0.3%  13.5KiB spirv_headers
 0.2%   0.3%  13.3KiB parking_lot
 1.5%   2.4%  96.6KiB And 36 more crates. Use -n N to show more.
61.5% 100.0%   4.0MiB .text section size, the file size is 6.5MiB

Well, I guess that I found that spirv_cross is used by other backends. So I want to disable other backends. I won't close the issue. It is indeed possible that other backends will involve some unused dependencies.

[kvark]

This is very informative, thank you!
Would you mind doing a local patch to wgpu-rs that doesn't enable "cross" feature in wpu-core? I'm curious to see the numbers when this feature isn't enabled.

[xhebox]

Here it is :)

[profile.release]
panic = "abort"
strip = "debuginfo"
lto = true

20.0%  26.7% 804.9KiB wgpu
12.1%  16.2% 487.0KiB std
10.3%  13.8% 416.0KiB naga
10.0%  13.4% 403.4KiB wgpu_core
 3.9%   5.3% 158.9KiB gfx_backend_gl
 3.4%   4.5% 136.5KiB wgpu_lut
 3.3%   4.4% 132.6KiB inplace_it
 2.4%   3.2%  97.4KiB hashbrown
 1.3%   1.8%  53.3KiB gfx_backend_vulkan
 1.0%   1.4%  41.3KiB gpu_descriptor
 0.9%   1.2%  35.2KiB ash
 0.7%   0.9%  28.0KiB spirv_headers
 0.5%   0.7%  21.1KiB async_io
 0.5%   0.7%  20.6KiB gfx_hal
 0.5%   0.6%  18.2KiB async_global_executor
 0.4%   0.6%  16.8KiB [Unknown]
 0.4%   0.5%  14.8KiB glow
 0.4%   0.5%  14.1KiB parking_lot
 0.3%   0.4%  11.0KiB miniz_oxide
 0.2%   0.3%   8.3KiB smallvec
 1.5%   2.0%  61.4KiB And 26 more crates. Use -n N to show more.
74.7% 100.0%   2.9MiB .text section size, the file size is 3.9MiB

I believe that wgpu can be made smaller somehow. You could also use cargo bloat to track the largest part in wgpu. link here.