As before, on the service side the GPU index the compositor runs on can be selected with
* XRT_COMPOSITOR_FORCE_GPU_INDEX=INDEX1
By default xrGetVulkanGraphicsDevice() will suggest the same GPU the compositor runs on.
It is also possible to override the GPU index suggested to applications with
* XRT_COMPOSITOR_FORCE_CLIENT_GPU_INDEX=INDEX2
The reason this is both done on the service side is that if compositor and client run
on different GPUs, the swapchains use linear tiling instead of optimal tiling.
To make chosen GPUs comparable across the compositor's and the client's vulkan instance,
VkPhysicalDeviceIDProperties.deviceUUID is used.
This patch passes the offset and extent properties to the layer shader
by extending the uniform. The fragment shader stage now also receives
the transformation uniform, which contains a has_sub boolean to
distinguish if the properties are set, so between projection and quad layers.
To avoid color bleeding the subimage sampling happens on a global pixel
coordinates basis as ivec2 using the GLSL texelFetch function.
Projection layers will be sampled as before.
Many functions returned void and were assumed to always succeed, and some functions
returned only a bool to indicate vague success/failure.
Now that these functions get piped over IPC all of them have to be able to indicate
an IPC failure like for example an unreachable service.
With the xrt_result_t return type they now have the opportunity to report various
types of failures.
Instead of maintaining this chunk of code and build options, the Vulkan
loader can be used to load up validation. This has the advantage that no
layer name needs to be hard coded inside Monado, which was subject of
change recently.
Instead of using our own environment variable we can easily set the one
from the loader, e.g. `VK_INSTANCE_LAYERS=VK_LAYER_KHRONOS_validation`.
This fixes a regression introduced by the IPC and layer rendering
patchsets and passes the array_index to the correct places, so the
correct VkImageView is used instead of the one with index 0.
