[core, hal, types] Clarify wgpu_hal's bounds check promises.

[jimblandy]

• [core, hal, types] Clarify wgpu_hal's bounds check promises.

  In wgpu_hal:

  • Document that wgpu_hal guarantees that shaders will not access buffer
    contents beyond the bindgroups' bound regions, rounded up to some
    adapter-specific alignment. Introduce the term "accessible region" for
    the portion of the buffer that shaders can actually get at.

  • Document that all bets are off if you disable bounds checks with
    ShaderModuleDescriptor::runtime_checks.

  • Provide this alignment in wgpu_hal::Alignments. Update all backends
    appropriately.

  • In the Vulkan backend, use Naga to inject bounds checks on buffer accesses
    unless robustBufferAccess2 is available; robustBufferAccess is not
    sufficient. Retrieve VK_EXT_robustness2's properties, as needed to discover
    the alignment above.

  In wgpu_core:

  • Use buffer bindings' accessible regions to determine which parts of the buffer
    need to be initialized.

  In wgpu_types:

  • Document some of the possible effects of using
    ShaderBoundsChecks::unchecked.

• [core]: Let Device::create_buffer_binding get limits from self.

  Rather than passing self.limits to Device::create_buffer_binding
  as an argument, let it simply refer to self.limits itself.

• [core] Remove unnecessary pub(crate) from Device methods.

  Remove the pub(crate) visibility marking from various associated
  functions of Device that are defined in, and not used outside of,
  the wgpu_core::device::resource module.

• [core] Simplify self types in device::resource.

  Change various functions that have no need to create an owning
  reference to the Device to accept &self instead of &Arc<Self>.

  Change ParentDevice::same_device to accept &Device as the point of
  comparison, not &Arc<Device>. Call sites will use Deref conversion,
  so no callers need to be changed.

• [core] Rename map_buffer to resolve_buffer, etc.

  In Device::create_bind_group, name the functions that convert
  resource ids to Arcs resolve_foo, not map_foo:

  • The types that hold Arcs are usually called ResolvedBlah.

  • The name map_buffer is misleading.

Fixes #1813.

Checklist

• Run cargo fmt.
• Run cargo clippy.
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.

[nical]

Beautiful.

[teoxoy]

Looks great!