Viewport: hidden edges no longer show through faces, and thin or coplanar faces stop z-fighting (#1434, #1739) (#1768)

Thanks @CamWight.

crates/ui-egui/src/gpu.rs

@@ -142,6 +142,7 @@ pub(crate) fn offscreen_device() -> Option<(wgpu::Adapter, wgpu::Device, wgpu::Q
     let instance = wgpu::Instance::new(desc);
     let adapter = pollster::block_on(instance.request_adapter(&Default::default())).ok()?;
     let (device, queue) = pollster::block_on(adapter.request_device(&wgpu::DeviceDescriptor {
+        required_features: solidcraft_gpu::depth_features(&adapter),
         required_limits: wgpu::Limits::downlevel_defaults().using_resolution(adapter.limits()),
         ..Default::default()
     }))
@@ -253,7 +254,7 @@ fn offscreen(
     let (adapter, device, queue) = offscreen_device()?;
     eprintln!("offscreen adapter: {:?}", adapter.get_info().backend);
     let format = if srgb { wgpu::TextureFormat::Rgba8UnormSrgb } else { wgpu::TextureFormat::Rgba8Unorm };
-    let depth = wgpu::TextureFormat::Depth24PlusStencil8;
+    let depth = solidcraft_gpu::depth_format(&device, true);
     let compute = tess.and_then(|shader| solidcraft_gpu::view::tessellation(&adapter, &device, &queue, shader));
     let target = GpuTarget { format, depth: Some(depth), samples: 1, tess: compute.is_some() };
     let mut resources = egui_wgpu::CallbackResources::default();