Update SPIRV-Cross to support dynamic indexing on iOS 10... and to
actually support arrays of input buffers (which should've been present
before I flipped the `shader{Uniform,Storage}BufferArrayDynamicIndexing`
switch).
Bump patch version.
Fixes#96.
Metal currently requires at least one attachment, in order to define the
size of the render target area (and thus, how many times to run the
fragment shader). Vulkan, however, allows specifying no attachments. In
that case, the size of the render target area comes from the extent and
layer count of the framebuffer object. Since Metal doesn't let you (at
least on macOS) define the render target area without an attachment, we
have to supply a dummy attachment that will be discarded once rendering
is complete.
When possible, the render target uses the memoryless storage mode,
falling back to private when that isn't supported. It is marked as
volatile, and its load and store actions are set to "don't care." The
texture is retained for the lifetime of the subpass.
Copying the results could block if the client said to wait. If this
completion handler runs before the one that actually finishes the
queries--and it will if it's scheduled first--it will block
indefinitely, causing a deadlock. Instead, run this on a different
dispatch queue; then the query will be allowed to finish.
Now when we set up the `MTLRenderPassAttachmentDescriptor` for the 3D
texture, we set the `depthPlane` property instead of the `slice`
property. Combined with an appropriate setting for
`renderTargetArrayLength` in the base descriptor, this allows rendering
to a subset of a 3D texture.
These properties were introduced in Metal 2.0 on iOS. (They don't exist
yet on Mac.) Currently, they are only used to constrain the size of the
render target area. Perhaps someday, they may be used to support render
passes with no render target attachments. For now, though, Metal doesn't
support that.
We already support this extension. The enumerant added by this extension
is already mapped to its Metal equivalent. Only advertise the extension
on macOS, though. iOS doesn't support this.
It's not convenient to get the usage out of the `pCreateInfo`, since
it's tucked away in an extension struct. (Unfortunately, I had assumed
we were already doing this...)
We don't really restrict which usages you can request on an image, so
the `VK_IMAGE_CREATE_EXTENDED_USAGE_BIT` doesn't really apply to us.
Since we don't yet support tessellation, we don't support
`VkPipelineTessellationDomainOriginStateCreateInfo`, either. Finally,
as near as I can tell, we don't really do anything with input
attachments, so any `VkRenderPassInputAttachmentAspectCreateInfo` will
be ignored.
I'm not sure if creating image views of compressed images using an
uncompressed format will work. Metal's docs say texture views between
any two color formats of the same size will work, but they also
specifically call out converting between sRGB and non-sRGB compressed
formats, which implies that, say, creating an `RG32Uint` view on a
`BC1_RGBA` texture may not work. Thus, I've logged any uses of the
`VK_IMAGE_CREATE_BLOCK_TEXEL_VIEW_COMPATIBLE_BIT`.
We don't actually do anything with the extension struct, but that's OK;
it's just an optimization hint anyway. I'm not sure what we'd do with
this information. It's intended to enable implementations to better
optimize image layouts, but that's under Metal's control in MoltenVK.
This is used to declare that a `VkDeviceMemory` object is for the sole
use of a particular buffer or image.
In fact, until Metal 1.2 on iOS (2.0 on Mac), Metal didn't really
support anything *but* dedicated allocations. MoltenVK hacks around this
limitation by manually syncing memory between buffers and images that
used the `VkDeviceMemory` object.
Maybe someday we can use the new `MTLHeap` object to support some sort
of sub-allocation scheme. But at this moment, it won't let you specify
the exact offset within the heap, nor can it be used for managed or (on
macOS) shared memory, nor will it let you directly map the heap memory
(something that could be worked around with an aliasable `MTLBuffer`
taking up the entire heap space), all of which makes it unsuitable for
implementing `VkDeviceMemory`. So, for now, we always prefer dedicated
allocation.
