nokwha::query(ApiBackend::MediaFoundation) causes panic on Windows w/ no cam plugged in

[njrogie]

On windows, desktop PC, no builtin camera, I ran the following code:

let cameras = nokhwa::query(ApiBackend::MediaFoundation);
match cameras {
    Err(err) => {
        info!("No cameras present!");
    }, 
    Ok(cameras) => {
         for (idx, camera) in cameras.iter().enumerate() {
              info!("{}: {}", idx, camera.human_name())
         }
    }
}

When i plug my usb webcam in, i get the following output:

0: NexiGo N60 FHD Webcam

When no camera is plugged in, the windows bindings panic.

thread 'tests::test_print_info' panicked at core\src\panicking.rs:221:5:
unsafe precondition(s) violated: slice::from_raw_parts requires the pointer to be aligned and non-null, and the total size of the slice not to exceed `isize::MAX`
stack backtrace:
   0: std::panicking::begin_panic_handler
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/std\src\panicking.rs:662
   1: core::panicking::panic_nounwind_fmt::runtime
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/core\src\panicking.rs:112
   2: core::panicking::panic_nounwind_fmt
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/core\src\panicking.rs:122
   3: core::panicking::panic_nounwind
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/core\src\panicking.rs:221
   4: core::slice::raw::from_raw_parts::precondition_check
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library\core\src\ub_checks.rs:70
   5: core::slice::raw::from_raw_parts<enum2$<core::option::Option<windows::Windows::Win32::Media::MediaFoundation::IMFActivate> > >
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library\core\src\ub_checks.rs:77
   6: nokhwa_bindings_windows::wmf::query_activate_pointers
             at C:\Users\njrog\.cargo\registry\src\index.crates.io-6f17d22bba15001f\nokhwa-bindings-windows-0.4.1\src\lib.rs:278
   7: nokhwa_bindings_windows::wmf::query_media_foundation_descriptors
             at C:\Users\njrog\.cargo\registry\src\index.crates.io-6f17d22bba15001f\nokhwa-bindings-windows-0.4.1\src\lib.rs:365
   8: nokhwa::query::query_msmf
             at C:\Users\njrog\.cargo\registry\src\index.crates.io-6f17d22bba15001f\nokhwa-0.10.5\src\query.rs:269
   9: nokhwa::query::query
             at C:\Users\njrog\.cargo\registry\src\index.crates.io-6f17d22bba15001f\nokhwa-0.10.5\src\query.rs:98
  10: display_video::impl$0::default
             at .\src\lib.rs:12
  11: display_video::tests::test_print_info
             at .\src\lib.rs:39
  12: display_video::tests::test_print_info::closure$0
             at .\src\lib.rs:38
  13: core::ops::function::FnOnce::call_once<display_video::tests::test_print_info::closure_env$0,tuple$<> >
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library\core\src\ops\function.rs:250
  14: core::ops::function::FnOnce::call_once
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/core\src\ops\function.rs:250

Seems like the windows bindings may need to be updated to handle a 'no-camera' state?

[njrogie]

I see now that this issue was fixed months ago in nokhwa-bindings-windows. However, when cargo installs the bindings crate to my registry (crates.io), it seems to install an older version of the lib.rs file.

[njrogie]

On returning to this today, I'd really like to be able to compile from source in windows to be able to use the most recent code. However, the build for nokhwa-core is broken at the moment (errors attached). Is there a correct way to get the build to work?

PS G:\Code\nokhwa> cargo build
   Compiling num-traits v0.2.19
   Compiling cfg-if v1.0.0
   Compiling scopeguard v1.2.0
   Compiling bytemuck v1.20.0
   Compiling serde v1.0.197
   Compiling libc v0.2.153
   Compiling futures-sink v0.3.30
   Compiling futures-core v0.3.30
   Compiling byteorder v1.5.0
   Compiling syn v2.0.87
   Compiling arrayvec v0.7.4
   Compiling bytes v1.6.0
   Compiling lock_api v0.4.11                                                                                                                                                                
   Compiling getrandom v0.2.12                                                                                                                                                               
   Compiling mozjpeg-sys v2.1.0
   Compiling nanorand v0.7.0
   Compiling rgb v0.8.37
   Compiling spin v0.9.8
   Compiling mozjpeg v0.10.7
   Compiling flume v0.11.0
   Compiling num-integer v0.1.46
   Compiling image v0.25.0
   Compiling thiserror-impl v2.0.0
   Compiling thiserror-impl v1.0.69
   Compiling num-rational v0.4.2
   Compiling thiserror v1.0.69
   Compiling thiserror v2.0.0
   Compiling nokhwa-core v0.2.0 (G:\Code\nokhwa\nokhwa-core)
error[E0583]: file not found for module `query`
  --> nokhwa-core\src\lib.rs:32:1
   |
32 | pub mod query;
   | ^^^^^^^^^^^^^^
   |
   = help: to create the module `query`, create file "nokhwa-core\src\query.rs" or "nokhwa-core\src\query\mod.rs"
   = note: if there is a `mod query` elsewhere in the crate already, import it with `use crate::...` instead

error[E0432]: unresolved import `crate::camera::AsyncCamera`
  --> nokhwa-core\src\platform.rs:1:21
   |
1  | use crate::camera::{AsyncCamera, Camera};
   |                     ^^^^^^^^^^^ no `AsyncCamera` in `camera`
   |
note: found an item that was configured out
  --> nokhwa-core\src\camera.rs:65:11
   |
65 | pub trait AsyncCamera: Camera + AsyncSetting + AsyncStream {}
   |           ^^^^^^^^^^^
note: the item is gated behind the `r#async` feature
  --> nokhwa-core\src\camera.rs:64:7
   |
64 | #[cfg(feature = "async")]
   |       ^^^^^^^^^^^^^^^^^

error[E0432]: unresolved import `crate::types::ApiBackend`
  --> nokhwa-core\src\error.rs:16:40
   |
16 | use crate::{frame_format::FrameFormat, types::ApiBackend};
   |                                        ^^^^^^^^^^^^^^^^^ no `ApiBackend` in `types`

warning: unexpected `cfg` condition value: `test-fail-warning`
 --> nokhwa-core\src\lib.rs:6:13
  |
6 | #![cfg_attr(feature = "test-fail-warning", deny(warnings))]
  |             ^^^^^^^^^^-------------------
  |                       |
  |                       help: there is a expected value with a similar name: `"test-fail-warnings"`
  |
  = note: expected values for `feature` are: `async`, `async-trait`, `default`, `docs-features`, `futures`, `opencv`, `opencv-mat`, `serde`, `serialize`, `test-fail-warnings`, `wgpu`, and `wgpu-types`
  = help: consider adding `test-fail-warning` as a feature in `Cargo.toml`
  = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
  = note: `#[warn(unexpected_cfgs)]` on by default

error[E0599]: the method `as_display` exists for reference `&Backends`, but its trait bounds were not satisfied
   --> nokhwa-core\src\error.rs:59:13
    |
59  |     #[error("This operation is not supported by backend {0}.")]
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ method cannot be called on `&Backends` due to unsatisfied trait bounds
    |
   ::: nokhwa-core\src\platform.rs:6:1
    |
6   | pub enum Backends {
    | ----------------- doesn't satisfy `Backends: std::fmt::Display`
    |
    = note: the following trait bounds were not satisfied:
            `Backends: std::fmt::Display`
            which is required by `&Backends: AsDisplay<'_>`
note: the trait `std::fmt::Display` must be implemented
   --> C:\Users\njrog\.rustup\toolchains\stable-x86_64-pc-windows-msvc\lib/rustlib/src/rust\library\core\src\fmt\mod.rs:724:1
    |
724 | pub trait Display {
    | ^^^^^^^^^^^^^^^^^
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `as_display`, perhaps you need to implement it:
            candidate #1: `AsDisplay`

error[E0277]: the `?` operator can only be used on `ControlFlow`s in a method that returns `ControlFlow`
   --> nokhwa-core\src\properties.rs:198:42
    |
189 |     pub fn validate(&self, value: &ControlValue) -> ControlFlow<()> {
    |     --------------------------------------------------------------- this function returns a `ControlFlow`
...
198 |                     int_range.validate(i)?;
    |                                          ^ this `?` produces `Result<Infallible, RangeValidationFailure>`, which is incompatible with `ControlFlow<()>`
    |
    = help: the trait `FromResidual<Result<Infallible, RangeValidationFailure>>` is not implemented for `ControlFlow<()>`
    = help: the trait `FromResidual<ControlFlow<(), Infallible>>` is implemented for `ControlFlow<()>`
    = help: for that trait implementation, expected `ControlFlow<(), Infallible>`, found `Result<Infallible, RangeValidationFailure>`

error[E0277]: the `?` operator can only be used on `ControlFlow`s in a method that returns `ControlFlow`
   --> nokhwa-core\src\properties.rs:208:44
    |
189 |     pub fn validate(&self, value: &ControlValue) -> ControlFlow<()> {
    |     --------------------------------------------------------------- this function returns a `ControlFlow`
...
208 |                     float_range.validate(i)?;
    |                                            ^ this `?` produces `Result<Infallible, RangeValidationFailure>`, which is incompatible with `ControlFlow<()>`
    |
    = help: the trait `FromResidual<Result<Infallible, RangeValidationFailure>>` is not implemented for `ControlFlow<()>`
    = help: the trait `FromResidual<ControlFlow<(), Infallible>>` is implemented for `ControlFlow<()>`
    = help: for that trait implementation, expected `ControlFlow<(), Infallible>`, found `Result<Infallible, RangeValidationFailure>`

error[E0515]: cannot return value referencing temporary value
   --> nokhwa-core\src\properties.rs:335:9
    |
335 | /         match self {
336 | |             ControlValuePrimitive::Null => &ControlValue::Null,
337 | |             ControlValuePrimitive::Integer(i) => &ControlValue::Integer(*i),
    | |                                                   ------------------------- temporary value created here
338 | |             ControlValuePrimitive::BitMask(b) => &ControlValue::BitMask(*b),
...   |
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

error[E0515]: cannot return value referencing temporary value
   --> nokhwa-core\src\properties.rs:335:9
    |
335 | /         match self {
336 | |             ControlValuePrimitive::Null => &ControlValue::Null,
337 | |             ControlValuePrimitive::Integer(i) => &ControlValue::Integer(*i),
338 | |             ControlValuePrimitive::BitMask(b) => &ControlValue::BitMask(*b),
    | |                                                   ------------------------- temporary value created here
...   |
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

error[E0515]: cannot return value referencing temporary value
   --> nokhwa-core\src\properties.rs:335:9
    |
335 | /         match self {
336 | |             ControlValuePrimitive::Null => &ControlValue::Null,
337 | |             ControlValuePrimitive::Integer(i) => &ControlValue::Integer(*i),
338 | |             ControlValuePrimitive::BitMask(b) => &ControlValue::BitMask(*b),
339 | |             ControlValuePrimitive::Float(f) => &ControlValue::Float(*f),
    | |                                                 ----------------------- temporary value created here
340 | |             ControlValuePrimitive::String(s) => &ControlValue::String(s.clone()),
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

error[E0515]: cannot return value referencing temporary value
   --> nokhwa-core\src\properties.rs:335:9
    |
335 | /         match self {
336 | |             ControlValuePrimitive::Null => &ControlValue::Null,
337 | |             ControlValuePrimitive::Integer(i) => &ControlValue::Integer(*i),
338 | |             ControlValuePrimitive::BitMask(b) => &ControlValue::BitMask(*b),
339 | |             ControlValuePrimitive::Float(f) => &ControlValue::Float(*f),
340 | |             ControlValuePrimitive::String(s) => &ControlValue::String(s.clone()),
    | |                                                  ------------------------------- temporary value created here
    | |                                                  ------------------------------- temporary value created here
    | |                                                  ------------------------------- temporary value created here
    | |                                                  ------------------------------- temporary value created here
    | |                                                  ------------------------------- temporary value created here
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
    | |                                                  ------------------------------- temporary value created here
    | |                                                  ------------------------------- temporary value created here
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
    | |                                                  ------------------------------- temporary value created here
    | |                                                  ------------------------------- temporary value created here
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
    | |                                                  ------------------------------- temporary value created here
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

error[E0515]: cannot return value referencing temporary value
    | |                                                  ------------------------------- temporary value created here
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

error[E0515]: cannot return value referencing temporary value
   --> nokhwa-core\src\properties.rs:335:9
    |
335 | /         match self {
336 | |             ControlValuePrimitive::Null => &ControlValue::Null,
337 | |             ControlValuePrimitive::Integer(i) => &ControlValue::Integer(*i),
338 | |             ControlValuePrimitive::BitMask(b) => &ControlValue::BitMask(*b),
...   |
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
    | |                                                   ------------------------- temporary value created here
    | |                                                  ------------------------------- temporary value created here
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

error[E0515]: cannot return value referencing temporary value
   --> nokhwa-core\src\properties.rs:335:9
    |
335 | /         match self {
336 | |             ControlValuePrimitive::Null => &ControlValue::Null,
337 | |             ControlValuePrimitive::Integer(i) => &ControlValue::Integer(*i),
338 | |             ControlValuePrimitive::BitMask(b) => &ControlValue::BitMask(*b),
...   |
    | |                                                  ------------------------------- temporary value created here
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

error[E0515]: cannot return value referencing temporary value
   --> nokhwa-core\src\properties.rs:335:9
    |
335 | /         match self {
336 | |             ControlValuePrimitive::Null => &ControlValue::Null,
    | |                                                  ------------------------------- temporary value created here
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

error[E0515]: cannot return value referencing temporary value
   --> nokhwa-core\src\properties.rs:335:9
    |
    | |                                                  ------------------------------- temporary value created here
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

error[E0515]: cannot return value referencing temporary value
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

    | |_________^ returns a value referencing data owned by the current function

error[E0515]: cannot return value referencing temporary value
   --> nokhwa-core\src\properties.rs:335:9
    |
335 | /         match self {
336 | |             ControlValuePrimitive::Null => &ControlValue::Null,
337 | |             ControlValuePrimitive::Integer(i) => &ControlValue::Integer(*i),
338 | |             ControlValuePrimitive::BitMask(b) => &ControlValue::BitMask(*b),
...   |
341 | |             ControlValuePrimitive::Boolean(b) => &ControlValue::Boolean(*b),
    | |                                                   ------------------------- temporary value created here
342 | |         }
    | |_________^ returns a value referencing data owned by the current function

Some errors have detailed explanations: E0277, E0432, E0515, E0583, E0599.
For more information about an error, try `rustc --explain E0277`.
warning: `nokhwa-core` (lib) generated 1 warning
error: could not compile `nokhwa-core` (lib) due to 11 previous errors; 1 warning emitted

[l1npengtul]

senpai is broken, have you tried using cargo update and using nokhwa 0.10.7?

[njrogie]

Here's my cargo.toml (the project is to try to display the camera feed in egui, which isn't quite relevant to this issue but it's worth mentioning).

[package]
name = "display-video"
version = "0.1.0"
edition = "2021"

[dependencies]
# egui
eframe = { version = "0.30.0", features = ["default"] }
epaint = { version = "0.30.0" }

# nokhwa  
nokhwa = { version = "0.10.7", features = ["input-msmf"]}

# Logging
env_logger = { version = "0.11.5", default-features = false, features = [
    "auto-color",
    "humantime",
] }
log = "0.4.22"

after running cargo update I still have the older nokwha-bindings-windows stored in .cargo\registry\src and .cargo\registry\cache. So i deleted the stored crate on my computer and re-downloaded it. The downloaded version from crates.io for nokwha-bindings-windows 0.4.2 continues to have the bug in it, even when the nokwha version is set to 0.10.7.

[njrogie]

Also, I wanted to know whether you would be open to a PR for fixing the senpai build?