Memory increased by a few GB when window is occluded by other windows on macOS.

[newDINO]

Description
On macOS, when a wgpu+winit program's window is fully occluded by other windows:

1. Its memory usage is increased by a few gigabytes.
2. The number of threads it uses is also increased.
3. Builtin Apple apps don't usually trigger this, other apps like vscode, chrome, blender can trigger it.
4. The memory increased seems to be related with the size of the command buffer. For example, if there is no render pass, there is basically no memory increase; if there is 1 pass, it uses around 1.2G; if there are 2 passes, it uses around 1.7G.
5. The issue still exists after I reboot the system.
6. If you bring the occluded wgpu+winit window back to the front, the memory usage will drop back to within 1G, but still a few times higher than the initial memory usage, probably because the memory allocator doesn't totally release those memories back.

Repro steps

1. Run example 02_hello_window in wgpu repo.
2. Open another window, or bring a maximized window to the front (use the apps listed in the 3rd point of Description to trigger the issue more easily).

Expected vs observed behavior
The total memory used by the wgpu program is increased by around 1GB.

Extra materials
I can provide a screen recording demonstrating the process if you want.

Platform
macOS 26.2
rust version: 1.93.0
wgpu version: 28.0
winit version: 0.30.12 (or 0.30.8 for the reproduction example)

AdapterInfo { name: "Apple M4", vendor: 0, device: 0, device_type: IntegratedGpu, device_pci_bus_id: "", driver: "", driver_info: "", backend: Metal, subgroup_min_size: 4, subgroup_max_size: 64, transient_saves_memory: true }

[newDINO]

A solution at user end is to listen to winit::event::WindowEvent::Occluded and don't do any rendering when the window is occluded. This can also help save CPU and memory usage on other platforms.

[inner-daemons]

This is a strange issue. I wonder if its come up in any of the other apps you mentioned? If its a super common issue on macOS and if the solution is to not render when the window is occluded, I think it might not be something wgpu needs to fix.

I am still very confused about how the window being occluded or not could affect memory though. Honestly very curious to see any more details.

I did ask on a graphics programming discord, we'll see if anyone there has anything to say.