When that setting is enabled, m_xfb_entry is initially not present (during the phase where a shader compilation progress bar would be shown). The main path checks for m_xfb_entry, but the software renderer fallback path didn't.
Fixes another aspect of https://bugs.dolphin-emu.org/issues/13172.
Before, it used a fallback where it returned a default object, where the width and height were set to 0. Presenter::Initialize() used GetSurfaceInfo to set the backbuffer size, then used that size when initializing the on-screen UI (even for the software renderer, where the on-screen UI isn't currently present), which meant that ImGui got a window size of 0 and thus resulted in a failed assertion.
Although BindBackbuffer checks for size changes, it doesn't help because ImGui has already been initialized, and the size hasn't actually changed since initialization occured.
Fixes one aspect of https://bugs.dolphin-emu.org/issues/13172.
The HLSL compiler incorrectly decides isnan can't be true, so this
workaround was originally added in 52c82733 but lost during the
conversion to SPIR-V.
When faced with this error, users often don't try disabling dual core,
even though the error message suggests it. Perhaps the message is just
too long and lists too many things?
To try to improve the situation, I'm rewording the message and making it
say different things depending on what settings you are using.
This works around an Intel driver bug where, on D3D12 only, dual-source blending behaves incorrectly if the second source is unused on. This bug is visible in skyboxes in Super Mario Sunshine, which first draw clouds and sun flare in greyscale and then draw the sky afterwards with a source factor of 1 and a dest factor of 1-src_color (this results in the clouds being tinted blue). This process is done on an RGB888 framebuffer, so alpha update is disabled. (Color update is enabled; note that if you look at this in Dolphin's fifo analyzer, it won't be enabled because they use the BP mask functionality to only change the blending functions and not alpha/color update, for whatever reason.)
While the NV extension is totally fine, the KHR extension should be able to support more hardware.
For NVIDIA, the hardware either supports both or neither, it just needs a driver from the last two years.
For AMD, the drivers from late 2022-12 seems to bring support for the KHR extension.
For Intel, the KHR is also supported for some years.
