Added option to disable smooth scrolling in list and compact modes

[tsujan]

The reason is that Qt may slow down item sorting in the list and compact modes when the number of items is huge and scrolling is done per pixel (smooth scrolling itself isn't the cause of slowdown; see lxqt/libfm-qt#739 (comment)). As a workaround, the user can disable per-pixel scrolling by disabling smooth scrolling in those modes, although that isn't needed in most use cases.

[tsujan]

I don't know how many minutes I should wait before making a PR based on a merged PR for the integrated check to see the latter and not fail :( The current failure is a false positive.

[stefonarch]

It fails for me too:

[ 82%] Building CXX object pcmanfm/CMakeFiles/pcmanfm-qt.dir/view.cpp.o
[ 84%] Building CXX object pcmanfm/CMakeFiles/pcmanfm-qt.dir/launcher.cpp.o
/home/stef/git/lxqt/pcmanfm-qt/pcmanfm/view.cpp: In member function 'void PCManFM::View::updateFromSettings(PCManFM::Settings&)':
/home/stef/git/lxqt/pcmanfm-qt/pcmanfm/view.cpp:165:5: error: 'setScrollPerPixel' was not declared in this scope
  165 |     setScrollPerPixel(settings.scrollPerPixel());
      |     ^~~~~~~~~~~~~~~~~
make[2]: *** [pcmanfm/CMakeFiles/pcmanfm-qt.dir/build.make:364: pcmanfm/CMakeFiles/pcmanfm-qt.dir/view.cpp.o] Error 1

EDIT: didn't see the libfm-qt thing, ignore this, it works.

[Chiitoo]

Works for me so far.

Many thanks!

[tsujan]

@stefonarch, @Chiitoo
Thanks!

EDIT: didn't see the libfm-qt thing, ignore this, it works.

Yes, it depends on the latest git libfm-qt, whose last commit was merged a few minutes before this PR was made.