Due to being a compositor, kwin has to conform to some certain
interfaces. It means a lot of virtual functions and function tables to
integrate with C APIs. Naturally, we not always want to use every
argument in such functions.
Since we get -Wunused-parameter from -Wall, we have to plumb those
unused arguments in order to suppress compiler warnings at the moment.
However, I don't think that extra work is worth it. We cannot change or
alter prototypes in any way to fix the warning the desired way. Q_UNUSED
and similar macros are not good indicators of whether an argument is
used too, we tend to overlook putting or removing those macros. I've
also noticed that Q_UNUSED are not used to guide us with the removal no
longer needed parameters.
Therefore, I think it's worth adding -Wno-unused-parameter compiler
option to stop the compiler producing warnings about unused parameters.
It changes nothing except that we don't need to put Q_UNUSED anymore,
which can be really cumbersome sometimes. Note that it doesn't affect
unused variables, you'll still get a -Wunused-variable compiler warning
if a variable is unused.
Currently, the BufferInterface encapsulates all the kinds of client
buffers. This has become a somewhat annoying issue as we want to
reference the shm pool if a shm buffer is destroyed, or have custom
buffer readiness logic for linux dma-buf client buffers.
Implementing all of that with the current abstractions will be
challenging as there's no good separation between different client
buffer types.
This change splits the BufferInterface class in three sub-classes -
DrmClientBuffer, LinuxDmaBufV1ClientBuffer, and ShmClientBuffer.
In addition to that, this change fixes the broken buffer ref'ing api.
