queueFamilyIndexCount

queueFamilyIndexCount is a field used in the Vulkan API to indicate the number of queue family indices provided to describe one or more queue families. In Vulkan, a queue family represents a group of queues on a physical device that share capabilities, such as graphics, compute, or transfer. Some API structures and extensions allow specifying multiple queue families at once, for example when configuring device groups or multi-queue submissions. In these cases, an accompanying array holds the actual queue family indices, and queueFamilyIndexCount specifies how many indices are in that array.

In practice, queueFamilyIndexCount is paired with a corresponding list or array of queue family indices (commonly referred to as queueFamilyIndices). The length of that array must match the value of queueFamilyIndexCount. The exact semantics and the structures that use this pair vary by extension or feature set; the field is part of the pattern in Vulkan where a count is provided alongside a pointer to an array.

Type and validation: The count is typically a 32-bit unsigned integer (uint32_t). Valid indices reference existing queue families on the physical device, as reported by the device’s queue family properties. Correct usage requires that the number of indices and the contents of the index array conform to the specific Vulkan structure or extension being used.

See also: Vulkan queue families, VkQueueFamilyProperties, device groups, multi-queue submissions.