Previously a triggerbox_ui.h change triggered a complete UI
rebuild. This follows the concept of other editor_selection
lists which use forward declarations.
Editor::drop_regions() creates a new RegionInsertDrag()
with the region to drop to the timeline.
RegionInsertDrag is-a RegionMotionDrag is-a RegionDrag is-a Drag.
However the region does not yet exist on the timeline and
RegionView is NULL.
This will likely need an API change. e.g.
Directly pass the TimeDomain as argument. The information can
be provided by the region, or from the TimeAxisView or RouteUI
when dropping a new source/region.
This is in preparation for allowing to drag trigger-regions
or trigger-slots. Those will not use a static singleton
PublicEditor API.
Additionally this constrains Ardour-internal drags to Ardour
(via Gtk::TARGET_SAME_APP).
This breaks windows builds, since apparently build(bld) is
evaluated twice (once to write compile_commands.json and once
to compile), even though `obj` is reset.
eg. in libs/pbd/wscript
```
if bld.env['build_target'] == 'mingw':
obj.source += [ 'windows_special_dirs.cc' ]
```
results in
[ 65/1159] Compiling libs/pbd/windows_special_dirs.cc
[ 69/1159] Compiling libs/pbd/windows_special_dirs.cc
which then produces an error when linking:
```
/usr/bin/x86_64-w64-mingw32-ld: libs/pbd/windows_special_dirs.cc.2.o:libs/pbd/windows_special_dirs.cc:28: multiple definition of `PBD::get_win_special_folder_path[abi:cxx11](int)'; libs/pbd/windows_special_dirs.cc.2.o:libs/pbd/windows_special_dirs.cc:28: first defined here
```
This enables the generation of build/compile_commands.json
which is a compilation database recognized by some IDE/editors
to provide compiler quality linting.
To name a few:
- Visual Studio Code
- VIM (with ALE plugin)
