Keeps associated data together. It also eliminates the possibility of out
parameters not being initialized properly. For example, consider the
following example:
-- some FramebufferManager implementation --
void FBMgrImpl::GetTargetSize(u32* width, u32* height) override
{
// Do nothing
}
-- somewhere else where the function is used --
u32 width, height;
framebuffer_manager_instance->GetTargetSize(&width, &height);
if (texture_width != width) <-- Uninitialized variable usage
{
...
}
It makes it much more obvious to spot any initialization issues, because
it requires something to be returned, as opposed to allowing an
implementation to just not do anything.
There's not a lot of point in passing these around or storing them
(texture cache/state tracker mainly) as there will only ever be a single
instance of the class.
Also adds downcast helpers such as Vulkan::Renderer::GetInstance().
