Supported backends

• GHOST_SystemSDL
• GHOST_SystemWayland
• GHOST_SystemWin32
• GHOST_SystemX11
• GHOST_SystemCocoa: using vulkan metal wrapper.

Compile directive

There will be a new compile directive WITH_VULKAN_BACKEND this compile directive will enable adding vulkan context in ghost backend systems.

Creating a vulkan context
Vulkan contexts can be created by passing GHOST_kDrawingContextTypeVulkan when creating window/context.

Device selection
There can be multiple vulkan compatible devices inside a system. User should be able to select a device via the user preferences. When selecting a different device blender should be restarted by the user. When no specific device is selected a best matching device should be selected.

GHOST_VulkanDeviceListHandle* GHOST_GetVulkanAvailableDevices(GHOST_SystemHandle,...): returns a list of all devices that match requirements. When constructing a window/context a specific device should be given.
int64_t GHOST_VulkanDeviceListNumDevices(GHOST_VulkanDeviceListHandle* handle) will return the number of devices found
GHOST_Success GHOST_GetVulkanDeviceListItem(GHOST_VulkanDeviceListHandle* handle, int64_t index, GHOST_VulkanPhysicalDevice * r_device) will fill r_device with available data return the vendor and device id and a number to make the device unique.
GHOST_DestroyVulkanDeviceList should be called to free the GHOST_VulkanDeviceListHandle.

GHOST_VulkanPhysicalDevice is based on VkPhysicalDeviceProperties but has a additional attribute to make the Vendor+Device unique. the combination of those 3 fields will allow to select a unique device.

struct GHOST_VulkanPhysicalDeviceID {
  uint32_t vendor_id;
  uint32_t device_id;
  int32_t index;
};

struct GHOST_VulkanPhysicalDevice {
  GHOST_VulkanPhysicalDeviceID device_id;
  VkPhysicalDeviceProperties device_properties;
};

GHOST_GLSettings will get an GHOST_VulkanPhysicalDeviceID* attribute for device selection.
When NULL is passed for GHOST_VulkanPhysicalDeviceID or the passed device couldn't be found during context creation GHOST will automatically select the best available device based on the device type (discrete before integrated before virtual [before cpu?]).

Command queues
GHOST_GetVulkanBackbuffer(GHOST_WindowHandle will get the handles of the given window.
For offscreen rendering GHOST_GetVulkanHandles will retrieve the device handles and the command queue etc should be constructed by the caller.

Smaller tasks

• Remove references to OpenGL in the GHOST API that are not OpenGL specific.
  • rename GHOST_CreateOpenGLContext to GHOST_CreateDrawingContext.
  • rename GHOST_DisposeOpenGLContext to GHOST_DisposeDrawingContext.
  • rename GHOST_ActivateOpenGLContext to GHOST_ActivateDrawingContext.
  • rename GHOST_ReleaseOpenGLContext to GHOST_ReleaseDrawingContext.
  • Unclear if we need to rename GHOST_GetDefaultOpenGLFramebuffer and GHOST_GetContextDefaultOpenGLFramebuffer or that we will have specific versions for Vulkan.