Fluid: restructuring and rejuvenation of the source code.

* Add classes for application and project
* Removed all globals from Fluid.h
* Extracting args and project history into their own classes
* Moving globals into Application class
* Initialize values inside headers for some classes.
* Undo functionality wrapped in a class inside Project.
* File reader and writer are now linked to a project.
* Avoid global project access
* Nodes (former Types) will be managed by a new Tree class.
* Removed static members (hidden globals) form Node/Fl_Type.
* Adding Tree iterator.
* Use nullptr instead of 0, NULL, or 0L
* Renamed Fl_..._Type to ..._Node, FL_OVERRIDE -> override
* Renaming ..._type to ...::prototype
* Splitting Widget Panel into multiple files.
* Moved callback code into widget panel file.
* Cleaning up Fluid_Image -> Image_asset
* Moving Fd_Snap_Action into new namespace fld::app::Snap_Action etc.
* Moved mergeback into proj folder.
* `enum ID` is now `enum class Type`.

1 files changed, 2 insertions, 2 deletions

diff --git a/fluid/widgets/Formula_Input.cxx b/fluid/widgets/Formula_Input.cxx
index b26bd83e3..dadebe674 100644
--- a/fluid/widgets/Formula_Input.cxx
+++ b/fluid/widgets/Formula_Input.cxx
@@ -1,5 +1,5 @@
 //
-// Widget type code for the Fast Light Tool Kit (FLTK).
+// Formula Int Input widget code for the Fast Light Tool Kit (FLTK).
 //
 // Copyright 1998-2025 by Bill Spitzak and others.
 //
@@ -209,7 +209,7 @@ int Formula_Input::handle(int event) {
 }
 
 /** Set the list of the available variables
- \param vars array of variables, last entry `has name_` set to `NULL`
+ \param vars array of variables, last entry `has name_` set to `nullptr`
  \param user_data is forwarded to the Variable callback */
 void Formula_Input::variables(Formula_Input_Vars *vars, void *user_data) {
   vars_ = vars;