[device] Implement find_queue_family_index_if

[IAmNotHanni]

The problem

We are in the process of getting rid of SettingsDecisionMakerentirely. When it comes to finding the right queue family indices, the old code contained several functions like this:

std::optional<std::uint32_t>
VulkanSettingsDecisionMaker::find_graphics_queue_family(const VkPhysicalDevice graphics_card) {
    assert(graphics_card);

    std::uint32_t number_of_available_queue_families = 0;

    // First check how many queue families are available.
    vkGetPhysicalDeviceQueueFamilyProperties(graphics_card, &number_of_available_queue_families, nullptr);

    spdlog::trace("There are {} queue families available", number_of_available_queue_families);

    // Preallocate memory for the available queue families.
    std::vector<VkQueueFamilyProperties> available_queue_families(number_of_available_queue_families);

    // Get information about the available queue families.
    vkGetPhysicalDeviceQueueFamilyProperties(graphics_card, &number_of_available_queue_families,
                                             available_queue_families.data());

    // Loop through all available queue families and look for a suitable one.
    for (std::size_t i = 0; i < available_queue_families.size(); i++) {
        if (available_queue_families[i].queueCount > 0) {
            // Check if this queue family supports graphics.
            if ((available_queue_families[i].queueFlags & VK_QUEUE_GRAPHICS_BIT) != 0) {
                // Ok this queue family supports graphics!
                return static_cast<std::uint32_t>(i);
            }
        }
    }

    // In this case we could not find any suitable graphics queue family!
    return std::nullopt;
}

That's a lot of code considering how little it does. Even worse, there was a lot of duplicate code like this!

The solution

All we need is:

std::optional<std::uint32_t> Device::find_queue_family_index_if(
    const std::function<bool(const std::uint32_t index, const VkQueueFamilyProperties &)> criteria_lambda) {
    std::uint32_t index = 0;
    for (const auto queue_family : vk_tools::get_all_physical_device_queue_family_properties(m_physical_device)) {
        if (queue_family.queueCount > 0 && criteria_lambda(index, queue_family)) {
            return index;
        }
        index++;
    }
    return std::nullopt;
}

I also implemented get_all_physical_device_queue_family_properties and is_presentation_supported. Now we can easily search for queue family indices as we like. All we need is to give a lambda to filter out the unsuitable queue family indices.

Examples

Need one which supports graphics and presentation?

std::optional<std::uint32_t> queue_candidate =
    find_queue_family_index_if([&](const std::uint32_t index, const VkQueueFamilyProperties &queue_family) {
        return is_presentation_supported(surface, index) &&
                  (queue_family.queueFlags & VK_QUEUE_GRAPHICS_BIT) != 0u;
    });

Need one which supports only transfer but no graphics?

std::optional<std::uint32_t> queue_candidate = find_queue_family_index_if([&](const std::uint32_t index, const VkQueueFamilyProperties &queue_family) {
            return is_presentation_supported(surface, index) &&
                   // No graphics bit, only transfer bit
                   (queue_family.queueFlags & VK_QUEUE_GRAPHICS_BIT) == 0u &&
                   (queue_family.queueFlags & VK_QUEUE_TRANSFER_BIT) != 0u;
        });

Closing remarks

Btw if we merge https://github.com/inexorgame/vulkan-renderer/pull/498 before this, we can get rid of SettingsDecisionMaker entirely! :) (we could also merge them in the other order and get remove it as well..)

Links

Vulkan spec chapter 5: Devices and Queues Stackoverflow question: What is actually a Queue family in Vulkan? Vulkan tutorial: Physical devices and queue families

[IAmNotHanni]

• [x] Fix clang-tidy warnings

[IceflowRE]

Would like to get a short overview what the difference to this https://github.com/inexorgame/vulkan-renderer/pull/489 is.

[IAmNotHanni]

@IceflowRE This pull request refactors the code which finds the queues we need to create the device. Pull request https://github.com/inexorgame/vulkan-renderer/pull/489 deals with finding the most suitable graphics card (or more general: physical device).