The gestures frame created its own log target and deleted
the previous one but did not restore it when being closed.
This left the current log target invalid which led to a crash
when calling any wxLog*() function after gestures frame was closed.
Fix this by restoring the previous log target when gestures frame
is closed.
Closes#23767.
See #23881.
This is a combination of running clang-tidy with modernize-use-nullptr
check for some ports (GTK, X11, OSX) and manual changes to the ports for
which it couldn't be used easily (MSW, DFB) and also manually updating
the docs.
Also replace NULL with null or nullptr in the comments as this is more
consistent with the use of nullptr in the code and makes it simpler to
grep for the remaining occurrences of NULL itself.
And also use null in the assert messages.
Only a few occurrences of "NULL" are still left in non-C files, mostly
corresponding to unclear comments or string output which it might not be
safe to change.
Don't load it from the image sample directory, this doesn't necessarily
work under Unix if the image sample hadn't been built.
Just embed an XPM image directly into the sample, this is good enough
for demonstration purposes.
Don't request touch event generation for all windows by default, this
has an inherent overhead and is not needed for 99% of the application
windows, so require calling EnableTouchEvents() explicitly to do it
instead.
Note that this requires properly initializing gesture recognizers in
wxOSX now that they're not always allocated, otherwise releasing them
when destroying the window would crash.