This simplifies the logging system.
This also fixes some lost messages on startup.
The simplification is simple. I removed unused functions and moved most things in the .h to the .cpp. I replaced the unnecessary linked list with its contents laid out as three member variables. Anything that went through the linked list now directly accesses the backends. Generic functions are replaced with those for each specific use case and there aren't many. This change increases coupling but we gain back more KISS and encapsulation.
With those changes it was easy to make it thread-safe. I just removed the mutex and turned a boolean atomic. I was planning to use this thread-safety in my next PR about stacktraces. It was actually async-signal-safety at first but I ended up using a different approach. Anyway getting rid of the linked list is important for that because have the list of backends constantly changing complicates things.
According to https://stackoverflow.com/questions/469508, we run into a
MSVC bug (since VS 2005) when using diamond inheritance for
RangedSetting.
This explicitly implements those functions in RangedSetting. GetValue is
implemented as just calling the inherited version. The explicit
converson operator is reimplemented. I opted for this over ignoring the
warning with a pragma since this specifies the inherited behavior, and I
have now less faith in MSVC to pick the right one.
In addition, we mark destructors as virtual to silence what I believe is
a fair MSVC compilation error.
This was mainly used to keep track of mapped buffers for later unmapping. Since unmap is no longer implemented, this no longer seves a valuable purpose.
With reference frames refreshes fix, we no longer need to buffer two frames in advance.
We can also remove other unused or otherwise unneeded variables.
Skip unmapping nvdec buffers to avoid breaking the continuity of the VP9 reference frame addresses, and the risk of invalidating data before the async GPU thread is done with it.
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