extension/ext: Add missing length-rounding in cmd_set_sample_mask() assert

[Macdu]

As stated in the vulkan specification for vkCmdSetSampleMaskEXT: https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/vkCmdSetSampleMaskEXT.html

sample_mask must be an array of size ceil(samples/32). However right now the ash wrapper for this function is checking that it is of size floor(samples/32), making this wrapper unusable for any sample count less than 32.

[Macdu]

Ah, div_ceil was only stabilized in Rust 1.73. Do you want me to rewrite this function the classic way ((samples.as_raw() + 31) / 32 as usize), or keep the fix as it is as it looks like you are planning to increase the MSRV anyway?

[MarijnS95]

That MSRV bump has already happened, to 1.69 which the CI is enforcing. We don't have a strict (written down) MSRV policy other than trying to not bump too eagerly (i.e. at least 6 months) and keeping them to semver-breaking releases.

Having div_ceil over hand-written rounding in two instances isn't enough to warrant an MSRV bump. On the other hand the October 5th release of Rust 1.73 is nearing that same 6-month mark, and could allow us to use more features added in those 4 releases in future patch-releases that we don't yet know about.

[Macdu]

I see, I changed the content of this PR so it doesn't use div_ceil anymore.

[MarijnS95]

We can make a separate PR to preemptively bump the MSRV if deemed necessary.

This PR also reminded me of an overwritten setter for VkPipelineMultisampleStateCreateInfo::pSampleMask in:

ash/generator/src/lib.rs

Lines 2014 to 2031 in 71387e9

	if name == "pSampleMask" {
	return Some(quote! {
	/// Sets `p_sample_mask` to `null` if the slice is empty. The mask will
	/// be treated as if it has all bits set to `1`.
	///
	/// See <https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VkPipelineMultisampleStateCreateInfo.html#_description>
	/// for more details.
	#[inline]
	pub fn sample_mask(mut self, sample_mask: &'a [SampleMask]) -> Self {
	self.p_sample_mask = if sample_mask.is_empty() {
	core::ptr::null()
	} else {
	sample_mask.as_ptr()
	};
	self
	}
	});
	}

This is to treat nullability properly (where Rust actually has a non-NULL pointer for &[] with length 0) and we might use that same override to also set rasterization_samples: vk::SampleCountFlags with similar validation to these commands, but not a requirement.

Also, just to make sure, unlike VkPipelineMultisampleStateCreateInfo, neither of these two cmd_set_sample_mask() functions allow pSampleMask to be NULL to "treat the mask as if all bits were set to 1".

[Macdu]

Also, just to make sure, unlike VkPipelineMultisampleStateCreateInfo, neither of these two cmd_set_sample_mask() functions allow pSampleMask to be NULL to "treat the mask as if all bits were set to 1".

Yes, the fact that pSampleMask has slightly different semantics in VkPipelineMultisampleStateCreateInfo compared to vkCmdSetSampleMaskEXT is a bit counter-intuitive (although at least the validation layer should be able to detect easily any misuse).

[MarijnS95]

Yeah, at least the VUID makes this clear on both cases (which is what the above statement is based on).