Fix panic in FpsOverlay with disabled FrameTimeGraph

[nekonimous]

Objective

I am getting the following panic on start:

thread 'main' panicked at /home/User/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/wgpu-26.0.1/src/backend/wgpu_core.rs:1195:26:
wgpu error: Validation Error

Caused by:
  In Device::create_bind_group, label = 'FrametimeGraphMaterial'
    Buffer with '' label binding size is zero


note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Encountered a panic in system `bevy_render::render_asset::prepare_assets<bevy_ui_render::ui_material_pipeline::PreparedUiMaterial<bevy_dev_tools::frame_time_graph::FrametimeGraphMaterial>>`!

when registering the FpsOverlayPlugin with the frame time graph disabled by default:

app.add_plugins(FpsOverlayPlugin {
    config: FpsOverlayConfig {
        text_config: TextFont {
            font_size: 18.0,
            ..Default::default()
        },
        frame_time_graph_config: FrameTimeGraphConfig {
            enabled: false, // causes panic above
            ..Default::default()
        },
        enabled: false,
        ..Default::default()
    },
})

Solution

I went with the most pragmatic fix I could find, since I am no render/shader expert but I can imagine there is a better way to fix this, please let me know. My reasoning being:

It does not panic after update_frame_time_values called buffer.set_data(frame_times.clone().as_slice()). So I ended up logging the buffer inside the system, and the first time it is called with empty frame_times it writes it into the ShaderStorageBuffer as [0, 0, 0, 0]. Doing the same when initializing the storage buffer fixes the panic on start.

[alice-i-cecile]

Comment about why this is needed please so we don't "clean this up". This also seems like a prime opportunity for a constructor on ShaderStorageBuffer for these sorts of patterns, but I won't block on that.

[nekonimous]

@alice-i-cecile I added a comment