It's tricky to always get the render area to the viewport code. In
particular, it's not provided to secondary command buffers as part of
the inheritance info so we have to bend over backwards and look for a
framebuffer. With VK_KHR_dynamic_rendering, there is no framebuffer and
this approach won't work and we'll need something better if we want
competent guardbands in secondary command buffers.
The good news is that any client that's sloppily rendering and trusting
the clipper to keep things inside the render area will set a scissor and
that's something they have to set inside the secondary. We can dig
through the scissor state and also include the corresponding scissor (if
any) and use that for our render area. This should give us the same
secondary command buffer performance with VK_KHR_dynamic_rendering.
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14961>
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