Silk.NET Structure Chaining

With the release of Silk.NET 2.11 we've enhanced the usability of Silk.NET.Vulkan by addressing one of its pain points, specifically building the Singly Linked Lists (or chains) of structures that are frequently used to pass information to, and from, the API.

Up until now, it was not unusual to have to write quite a lot of unsafe code to work with the Vulkan API. For example, to query device features you would need to create a chain of empty structures to be populated by the API:

var accelerationStructureFeaturesKhr = new PhysicalDeviceAccelerationStructureFeaturesKHR
    {SType = StructureType.PhysicalDeviceAccelerationStructureFeaturesKhr};
var indexingFeatures = new PhysicalDeviceDescriptorIndexingFeatures
{
    SType = StructureType.PhysicalDeviceDescriptorIndexingFeatures,
    PNext = &accelerationStructureFeaturesKhr
};
var features2 = new PhysicalDeviceFeatures2
{
    SType = StructureType.PhysicalDeviceFeatures2,
    PNext = &indexingFeatures
};
vk.GetPhysicalDeviceFeatures2(device, &features2);

Not only is this quite a bit of boiler plate (and it gets worse when you actually want to pass data to the API), it is really easy for developers, who are not always comfortable with unsafe code, memory management and pointers, to introduce subtle bugs by passing in pointers to structures they have previously generated and are now residing on the .NET heap. Such structures can be moved by the Garbage Collector at the most unexpected times!

Thanks to Structure Chaining, we now have 2 new ways to write the above code. The most useful Managed Chaining, makes it much easier, and safer, to work with Vulkan Structure Chains. For example, the above code can now be written as:

using var features2 = Chain.Create<PhysicalDeviceFeatures2, PhysicalDeviceDescriptorIndexingFeatures,
    PhysicalDeviceAccelerationStructureFeaturesKHR>();
vk.GetPhysicalDeviceFeatures2(device, features2);

The new Chain classes manage the lifetime of the structures for you and they can be safely stored on the heap, like any object. They also efficiently handle the SType and PNext fields, ensuring they are always correct. It is also easy to modify and manipulate the chains. What is less obvious from the above example is that we are now able to validate that PhysicalDeviceFeatures2 can be used as the start of a chain, and that both PhysicalDeviceDescriptorIndexingFeatures and PhysicalDeviceAccelerationStructureFeaturesKHR are valid structures to appear in such a chain. That validation occurs at compile time, meaning that most modern IDEs will give you error 'squiggles' as soon as you try and use an invalid structure (according to the Vulkan Specification)!

That 'magic' is possible due to a set of new interfaces we've added to Vulkan Structures to indicate when they can be used in chains, and, when the Vulkan Specification explicitly states it, what chains they can be used in. All without effecting runtime performance.

Full documentation is available here, and we can't wait for you to start using the new features! If they prove popular, we plan on expanding the functionality to other APIs supported by Silk.NET.