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, 131 insertions, 0 deletions

diff --git a/fluid/nodes/Widget_Node.h b/fluid/nodes/Widget_Node.h
new file mode 100644
index 000000000..261005590
--- /dev/null
+++ b/fluid/nodes/Widget_Node.h
@@ -0,0 +1,131 @@
+//
+// Widget Node header file 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
+//
+
+// Type for creating all subclasses of Fl_Widget
+// This should have the widget pointer in it, but it is still in the
+// Node base class.
+
+#ifndef FLUID_NODES_WIDGET_NODE_H
+#define FLUID_NODES_WIDGET_NODE_H
+
+#include "nodes/Node.h"
+
+#define NUM_EXTRA_CODE 4
+
+class Widget_Node;
+class Image_Asset;
+
+extern void* const LOAD;
+extern Widget_Node *current_widget; // one of the selected ones
+
+extern const char* subclassname(Node* l);
+extern int is_name(const char *c);
+void selection_changed(Node* new_current);
+Node *sort(Node *parent);
+
+class Widget_Node : public Node
+{
+  typedef Node super;
+
+  virtual Fl_Widget *widget(int,int,int,int) = 0;
+  virtual Widget_Node *_make() = 0; // virtual constructor
+  void setlabel(const char *) override;
+
+  const char *extra_code_[NUM_EXTRA_CODE];
+  const char *subclass_;
+  const char *tooltip_;
+  const char *image_name_;
+  const char *inactive_name_;
+  uchar hotspot_;
+
+protected:
+
+  /// This variable is set for visible windows in batch mode.
+  /// We can't open a window in batch mode, even if we want the "visible" flags
+  /// set, so we need a second place to store this information while also
+  /// disabling the output of the "hide" property by the Widget Type.
+  uchar override_visible_;
+
+  void write_static(fld::io::Code_Writer& f) override;
+  void write_code1(fld::io::Code_Writer& f) override;
+  void write_widget_code(fld::io::Code_Writer& f);
+  void write_extra_code(fld::io::Code_Writer& f);
+  void write_block_close(fld::io::Code_Writer& f);
+  void write_code2(fld::io::Code_Writer& f) override;
+  void write_color(fld::io::Code_Writer& f, const char*, Fl_Color);
+  Fl_Widget *live_widget;
+
+public:
+  Fl_Widget *o;
+  int public_;
+  int bind_image_;
+  int compress_image_;
+  int bind_deimage_;
+  int compress_deimage_;
+  int scale_image_w_, scale_image_h_;
+  int scale_deimage_w_, scale_deimage_h_;
+
+  Image_Asset *image;
+  void setimage(Image_Asset *);
+  Image_Asset *inactive;
+  void setinactive(Image_Asset *);
+
+  Widget_Node();
+  Node *make(Strategy strategy) override;
+  void open() override;
+
+  const char *extra_code(int n) const {return extra_code_[n];}
+  void extra_code(int n,const char *);
+  const char *subclass() const {return subclass_;}
+  void subclass(const char *);
+  const char *tooltip() const {return tooltip_;}
+  void tooltip(const char *);
+  const char *image_name() const {return image_name_;}
+  void image_name(const char *);
+  const char *inactive_name() const {return inactive_name_;}
+  void inactive_name(const char *);
+  uchar hotspot() const {return hotspot_;}
+  void hotspot(uchar v) {hotspot_ = v;}
+  uchar resizable() const;
+  void resizable(uchar v);
+
+  virtual int textstuff(int what, Fl_Font &, int &, Fl_Color &);
+  virtual Fl_Menu_Item *subtypes();
+
+  Type type() const override { return Type::Widget_; }
+  bool is_a(Type inType) const override { return (inType==Type::Widget_) ? true : super::is_a(inType); }
+  int is_widget() const override;
+  int is_true_widget() const override { return 1; }
+  int is_public() const override;
+
+  void write_properties(fld::io::Project_Writer &f) override;
+  void read_property(fld::io::Project_Reader &f, const char *) override;
+  int read_fdesign(const char*, const char*) override;
+
+  Fl_Widget *enter_live_mode(int top=0) override;
+  Fl_Widget *propagate_live_mode(Fl_Group* grp);
+  void leave_live_mode() override;
+  void copy_properties() override;
+
+  virtual void ideal_size(int &w, int &h);
+
+  ~Widget_Node();
+  void redraw();
+};
+
+extern Fl_Window *the_panel;
+
+#endif // FLUID_NODES_WIDGET_NODE_H