Fix Metal API violation when using VK_KHR_swapchain_mutable_format.

[stripe2933]

Texture view creation is not allowed from framebufferOnly textures. The flag should be disabled if texture view will be created from it.

Related: #2261

[CLAassistant]

All committers have signed the CLA.

[billhollings]

Good catch. Thanks for submitting this.

I've made a suggestion for streamlining the logic.

[stripe2933]

One thing I'm concerned about is setting framebufferOnly to false may disable the optimization. I'm not familiar with Metal, and I'm wondering is there a Metal specific way to treat the color attachment's format different from CAMetalLayer's format, without creating an alias texture for it.

[billhollings]

LGTM now. Thanks.

One thing I'm concerned about is setting framebufferOnly to false may disable the optimization.

Yes. This will definitely affect performance, as the Apple docs make clear. I guess mutable format is included in the "you may not sample, read from, or write" restrictions that leave Metal unable to use an optimized layout if the render target texture.

I'm not familiar with Metal, and I'm wondering is there a Metal specific way to treat the color attachment's format different from CAMetalLayer's format, without creating an alias texture for it.

AFAIK, the framebufferOnly flag is the Metal specific way of optimizing, and we have to live with its restrictions. I'd be happy to be proven wrong on this.