diff --git a/apps/effectcraft/src/main.rs b/apps/effectcraft/src/main.rs index 64ab5443d..452196224 100644 --- a/apps/effectcraft/src/main.rs +++ b/apps/effectcraft/src/main.rs @@ -378,9 +378,15 @@ fn main() -> eframe::Result { /// instead of eframe's fixed set: an older GPU that can't meet those (Intel HD Graphics 5500, /// #198) still opens the app, and the compositor then checks what it needs and falls back to /// the CPU when the device can't run it. `backends`: Window Graphics' choice, when it makes one. +/// +/// The surface is eframe's own default, [`eframe::SurfaceConfig::LOW_LATENCY`]: vsync with one +/// frame in flight, so a drag or a scrub shows one frame sooner. The bare +/// `WgpuConfiguration::default()` is `HIGH_THROUGHPUT` instead (two frames in flight, three +/// drawables on Metal): one more frame of pointer-to-screen lag on every interaction, about 8 ms +/// at 120 Hz and 17 ms at 60 Hz, and a third 15 MB drawable held for the window. fn wgpu_options(backends: Option) -> eframe::WgpuConfiguration { use eframe::egui_wgpu::WgpuSetup; - let mut config = eframe::WgpuConfiguration::default(); + let mut config = eframe::WgpuConfiguration::default().with_surface_config(eframe::SurfaceConfig::LOW_LATENCY); if let WgpuSetup::CreateNew(setup) = &mut config.wgpu_setup { if let Some(b) = backends { setup.instance_descriptor.backends = b; @@ -567,6 +573,19 @@ mod tests { assert!(!setup.instance_descriptor.flags.contains(eframe::wgpu::InstanceFlags::VALIDATION_INDIRECT_CALL)); } + /// The window's surface keeps one frame in flight, like eframe's own default, not the two + /// of the bare `WgpuConfiguration::default()` (one extra frame of lag on every drag). + #[test] + fn the_window_surface_is_low_latency() { + for backends in [None, Some(eframe::wgpu::Backends::METAL), Some(eframe::wgpu::Backends::GL)] { + let surface = super::wgpu_options(backends).surface; + assert_eq!(surface, eframe::SurfaceConfig::LOW_LATENCY, "{backends:?}"); + assert_eq!(surface.desired_maximum_frame_latency, Some(1)); + assert_eq!(surface.present_mode, eframe::wgpu::PresentMode::AutoVsync); + } + assert_eq!(super::wgpu_options(None).surface, eframe::NativeOptions::default().wgpu_options.surface, "eframe's default surface"); + } + /// The window's device never asks for more than the adapter offers (#198). #[test] fn device_limits_fit_the_adapter() {