Resizing swap buffers

[Luke Brown]

Hi, I was curious what the intended way is to resize swap buffers in dawn (for example when the window is resized)

I'm testing using the d3d12 implementation which I believe has support for resizing the buffers, but it looks as though dawn's native swap chain implementation does use that. Calling the "Configure" function again on the swap chain with a different size also seems to fail.

So far the only solution I can really see here is to destroy the current device and recreate it.

Any info would be greatly appreciated,

Luke

[Corentin Wallez]

On a phone, excuse brevity, but it should be possible to resize windows without recreating the device just using configure. See https://dawn.googlesource.com/dawn/+/refs/heads/main/src/dawn/samples/ManualSwapChainTest.cpp that are the tests we use to check the resizing works.

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[Luke Brown]

Thanks. I'll take a look

Luke

[Jean-Colas Prunier]

I am not part of the Dawn dev team, but I have been doing some tests with the API so maybe I can share my experience. Are you speaking about what you need to do when the window is resized? So far what has worked for me was to:

- Recreate the SwapChain with (with the new window size)

- Recreate the depth stencil view (with the new window size)

This was enough in my case. I didn't touch the `wgpu::Surface surface`, which I initialize at the beginning of the program. It's my understanding that it's the WSI's responsibility to adjust the surface when the window size changes but I am might be wrong. For my tests I used GLFW. Sorry if I didn't get your question right. I have tested this with the Vulkan backend. I also tried `swapChain.Configure(...)` but this didn't work for me. The only method that worked was the one I described above. Interested to hear from the Dawn developers if there's a better / other solution (or if this one is wrong).

[Corentin Wallez]

The approach you followed Jean-Colas should be the correct one and even though I implemented the thing I was wrong in the previous email. The way to resize surface-based swapchains (the only ones you should use, the others are deprecated and we want to remove them soon) is to recreate a swapchain on the same surface but with a different size. That's what the ManualSwapchainTest example does and we have previously checked it works on Windows, Linux and macOS with the various backends.

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[Luke Brown]

Thanks, that led to a solution.

We're using SDL2 for windowing and there wasn't a simple way in dawn, like with glfw, to get a surface for a SDL_Window so we were using the native swap chain implementation method instead. After reading you last reply I switched over to creating a wgpu Surface for the SDL_Window - or more accurately the HWND in this particular case (mostly taking code from the glfw utils and modifying it a bit) - and now that works perfectly.

Thanks for the help

Luke