This allows to copy a property list and then selectively
replace various properties. e.g.
```
PropertyList plist (region->properties ());
plist.add (Properties::length, len);
plist.remove (Properties::start);
```
See also 8b0ab38675
and 97f0fac7d5
This also fixes the issue referenced in
8c83149c4c
Found via `codespell -q 3 -S *.po,./.git,./share/patchfiles,./libs,./msvc_extra_headers,./share/web_surfaces,*.patch -L acount,ba,buss,busses,discreet,doubleclick,hsi,ontop,retrn,ro,scrollin,seh,siz,sord,sur,te,trough,ue`
Even though SIGINT is intended to be sent from terminals only,
it is more successful at terminating various child processes than
closing stdin and sending SIGTERM.
This ensures that the user will see a "POOL OUT OF MEMORY" message.
In rare case dumping the pool can segfault when printing the Event,
The pool is zero initialized and only ever contains events, so
in theory it is safe to print them..
It can happen that ::get_request() returns NULL if the
EventPool is full. In that case the slot is never called.
In this case the caller can now take action.
We discovered in the past that the C++ API for GSource/Glib::Source has some fatal and unfixable flaws. Copy similar
code and just use the C API for GSource instead
This is based on code from earlier commits that were later reversed, but we need some mechanism
to ensure that threads have a thread local tempo map ptr set. The big difference is that this
time we do not implement this for all instances of an AbstractUI - implementation is left to
each thread/event loop
On M1, the cross-thread channel sets G_IO_PRI in addition to G_IO_IN
this breaks various assumptions in receivers, which test for ~G_IO_IN
as error condition.
Return from poll_for_request() when CrossThreadChannel is
closed/destroyed. -- see also f4166fb61d
This also cleans up poll API usage, and check for nonnegative
return value is added.
