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, 55 insertions, 0 deletions

diff --git a/fluid/app/args.h b/fluid/app/args.h
new file mode 100644
index 000000000..80dfa2290
--- /dev/null
+++ b/fluid/app/args.h
@@ -0,0 +1,55 @@
+//
+// Command Line Arguments Handling header for the Fast Light Tool Kit (FLTK).
+//
+// Copyright 1998-2025 by Bill Spitzak and others.
+//
+// This library is free software. Distribution and use rights are outlined in
+// the file "COPYING" which should have been included with this file.  If this
+// file is missing or damaged, see the license at:
+//
+//     https://www.fltk.org/COPYING.php
+//
+// Please see the following page on how to report bugs and issues:
+//
+//     https://www.fltk.org/bugs.php
+//
+
+#ifndef FLUID_APP_ARGS_H
+#define FLUID_APP_ARGS_H
+
+#include <string>
+
+namespace fld {
+namespace app {
+
+class Args {
+  // Callback.
+  static int arg_cb(int argc, char** argv, int& i);
+  // Handle args individually.
+  int arg(int argc, char** argv, int& i);
+public:
+  /// Set, if Fluid was started with the command line argument -u
+  int update_file { 0 };            // fluid -u
+  /// Set, if Fluid was started with the command line argument -c
+  int compile_file { 0 };           // fluid -c
+  /// Set, if Fluid was started with the command line argument -cs
+  int compile_strings { 0 };        // fluid -cs
+  /// command line arguments that overrides the generate code file extension or name
+  std::string code_filename { };    // fluid -o filename
+  /// command line arguments that overrides the generate header file extension or name
+  std::string header_filename { };  // fluid -h filename
+  /// if set, generate images for automatic documentation in this directory
+  std::string autodoc_path { };         // fluid --autodoc path
+  /// Set, if Fluid was started with the command line argument -v
+  int show_version { 0 };           // fluid -v
+  /// Constructor.
+  Args() = default;
+  // Load args from command line into variables.
+  int load(int argc, char **argv);
+};
+
+} // namespace app
+} // namespace fld
+
+#endif // FLUID_APP_ARGS_H
+