Metal FeatureFamily change is now using incorrect enum values

[EvilTrev]

One of the more recent changes to renderer_mtl moved from MTLFeatureSet to MTLGPUFamily, however in many cases it is now using incorrect enum values and tests. For example here:

if (m_macOS11Runtime
|| [m_device supportsFamily:(MTLGPUFamily)4 /*MTLGPUFamily_iOS_GPUFamily3_v1*/])
{
	const uint32_t cmpFunc = (_flags&BGFX_SAMPLER_COMPARE_MASK)>>BGFX_SAMPLER_COMPARE_SHIFT;
	m_samplerDescriptor.compareFunction = 0 == cmpFunc
		? MTLCompareFunctionNever
		: s_cmpFunc[cmpFunc]
		;
}

Comparison sampling is supported from family "Common2" and "Apple3" up, and those enums are:

    MTLGPUFamilyCommon2 = 3002,
    MTLGPUFamilyApple3  = 1003,

As a result, samplers with comparisons do not work on iOS devices. There are other inconsistencies and errors in the metal renderer currently as a result of this change. I think it might be worth defining this enum (and maybe others) on platforms without the header to avoid magic numbers? Assuming that's the reason they are hardcoded constants?

[EvilTrev]

Here are the fixes:

g_caps.limits.maxTextureSize = m_device.supportsFamily( (MTLGPUFamily)1003 /* iOS_GPUFamily3_v1 */) ? 16384 : 8192;

g_caps.supported |= m_device.supportsFamily( (MTLGPUFamily)1003 /* MTLGPUFamily_iOS_GPUFamily3_v1 */)
	? BGFX_CAPS_DRAW_INDIRECT
	: 0
	;

g_caps.supported |= m_device.supportsFamily( (MTLGPUFamily)1004 /* MTLGPUFamily_iOS_GPUFamily4_v1 */)
	? BGFX_CAPS_TEXTURE_CUBE_ARRAY
	: 0
	;

g_caps.supported |= m_device.supportsFamily( (MTLGPUFamily)2002 /* MTLGPUFamily_macOS_GPUFamily1_v2 */)
	? BGFX_CAPS_DRAW_INDIRECT
	: 0
	;

if (m_macOS11Runtime
	|| [m_device supportsFamily:(MTLGPUFamily)1003 /*MTLGPUFamilyApple3*/]
	|| [m_device supportsFamily:(MTLGPUFamily)3002 /*MTLGPUFamilyCommon2*/])
	{
		const uint32_t cmpFunc = (_flags&BGFX_SAMPLER_COMPARE_MASK)>>BGFX_SAMPLER_COMPARE_SHIFT;
		m_samplerDescriptor.compareFunction = 0 == cmpFunc
			? MTLCompareFunctionNever
			: s_cmpFunc[cmpFunc]
			;
	}

[bkaradzic]

Good catch, Just submit PR with fixes.

[EvilTrev]

@bkaradzic my codebase isn't in a place where I can easily submit PRs unfortunately, so I'm just passing along the info for now :)

[bkaradzic]

Metal feature set tables
https://developer.apple.com/metal/Metal-Feature-Set-Tables.pdf

[fiserj]

@bkaradzic I think c43c447 and using the MTLGPUFamily enum values directly made the compilation fail on older versions of Xcode.

Would it make sense to add Xcode version detection like in MoltenVK (version macros defined here)?