BindGroupEntries

[robtfm]

Objective

Simplify bind group creation code. alternative to (and based on) bevyengine#9476

Solution

• Add a BindGroupEntries struct that can transparently be used where &[BindGroupEntry<'b>] is required in BindGroupDescriptors.

Allows constructing the descriptor's entries as:

render_device.create_bind_group(
    Some("my_bind_group"),
    &my_layout,
    BindGroupEntries::with_indexes((
        (2, &my_sampler),
        (3, my_uniform),
    )).as_slice(),
);

instead of

render_device.create_bind_group(
    Some("my_bind_group"),
    &my_layout,
    &[
        BindGroupEntry {
            binding: 2,
            resource: BindingResource::Sampler(&my_sampler),
        },
        BindGroupEntry {
            binding: 3,
            resource: my_uniform,
        },
    ],
);

or

render_device.create_bind_group(
    Some("my_bind_group"),
    &my_layout,
    BindGroupEntries::sequential((
        &my_sampler,
        my_uniform,
    )).as_slice(),
);

instead of

render_device.create_bind_group(
    Some("my_bind_group"),
    &my_layout,
    &[
        BindGroupEntry {
            binding: 0,
            resource: BindingResource::Sampler(&my_sampler),
        },
        BindGroupEntry {
            binding: 1,
            resource: my_uniform,
        },
    ],
);

the structs has no user facing macros, is tuple-type-based so stack allocated, and has no noticeable impact on compile time.

• Also adds a DynamicBindGroupEntries struct with a similar api that uses a Vec under the hood and allows extending the entries.
• Modifies RenderDevice::create_bind_group to take separate arguments label, layout and entries instead of a BindGroupDescriptor struct. The struct can't be stored due to the internal references, and with only 3 members arguably does not add enough context to justify itself.
• Modify the codebase to use the new api and the BindGroupEntries / DynamicBindGroupEntries structs where appropriate (whenever the entries slice contains more than 1 member).

Migration Guide

Calls to RenderDevice::create_bind_group({BindGroupDescriptor { label, layout, entries }) must be amended to RenderDevice::create_bind_group(label, layout, entries).

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