hello_compute: check for missing command-line args

[vilcans]

Connections
N/A

Description

Fixes off-by-one error when checking for missing arguments. Before this, running the example gave this discouraging error message:

$ cargo run --bin wgpu-examples hello_compute
    Finished dev [unoptimized + debuginfo] target(s) in 0.13s
     Running `target/debug/wgpu-examples hello_compute`
[2023-12-27T22:14:26Z ERROR wgpu::backend::direct] Handling wgpu errors as fatal by default
thread 'main' panicked at 'wgpu error: Validation Error

Caused by:
    In Device::create_bind_group
    Buffer binding size 0 is less than minimum 4
      note: buffer = `Storage Buffer`

', wgpu/src/backend/direct.rs:3139:5

As this was the first example I tried to run, it almost scared me away, thinking it was a driver issue.

Instead, without arguments the example should use defaults.

Testing

Tested from the command-line, now it uses defaults as it should:

$ cargo run --bin wgpu-examples hello_compute
    Finished dev [unoptimized + debuginfo] target(s) in 0.13s
     Running `target/debug/wgpu-examples hello_compute`
No numbers were provided, defaulting to [1, 2, 3, 4]
Steps: [0, 1, 7, 2]

Checklist

• Run cargo fmt.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
  • --target wasm32-unknown-emscripten
• Run cargo xtask test to run tests.
  • (they fail but that can't be related)
• Add change to CHANGELOG.md. See simple instructions inside file.

[Wumpf]

ah, thanks! That was apparently missed when the examples switched to a single binary, thus having two arguments in the beginning, one for executable path and one for the selected example