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.h b/fluid/widgets/Formula_Input.h
index 5307cdc88..060c1e157 100644
--- a/fluid/widgets/Formula_Input.h
+++ b/fluid/widgets/Formula_Input.h
@@ -1,5 +1,5 @@
 //
-// Formula_Input widget header file for the Fast Light Tool Kit (FLTK).
+// Formula Int Input widget header file for the Fast Light Tool Kit (FLTK).
 //
 // Copyright 1998-2025 by Bill Spitzak and others.
 //
@@ -29,7 +29,7 @@ typedef int (Fluid_Coord_Callback)(Formula_Input const *, void*);
 
 // Entry for a list of variables available to an input field.
 // Formula_Input::variables() expects an array of
-// Formula_Input_Vars with the last entry's name_ set to NULL.
+// Formula_Input_Vars with the last entry's name_ set to nullptr.
 typedef struct Formula_Input_Vars {
   const char *name_;
   Fluid_Coord_Callback *callback_;