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, 219 insertions, 0 deletions

diff --git a/fluid/Fluid.h b/fluid/Fluid.h
new file mode 100644
index 000000000..1857518ee
--- /dev/null
+++ b/fluid/Fluid.h
@@ -0,0 +1,219 @@
+//
+// Fluid Application 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_FLUID_H
+#define FLUID_FLUID_H
+
+#include "Project.h"
+#include "app/args.h"
+#include "app/history.h"
+#include "app/Snap_Action.h"
+#include "tools/filename.h"
+
+#include <FL/Fl_Preferences.H>
+#include <FL/Fl_Menu_Item.H>
+#include <FL/filename.H>
+
+#include <string>
+
+constexpr int BROWSERWIDTH = 300;
+constexpr int BROWSERHEIGHT = 500;
+constexpr int WINWIDTH = 300;
+constexpr int MENUHEIGHT = 25;
+constexpr int WINHEIGHT = (BROWSERHEIGHT+MENUHEIGHT);
+
+// ---- types
+
+class Fl_Double_Window;
+class Fl_Window;
+class Fl_Menu_Bar;
+class Node;
+class Fl_Choice;
+class Fl_Button;
+class Fl_Check_Button;
+class Fl_Help_Dialog;
+
+namespace fld {
+namespace app {
+class Layout_List;
+}
+
+/**
+ Indicate the storage location for tools like layout suites and shell macros.
+ \see class Fd_Shell_Command, class Layout_Suite
+ */
+enum class Tool_Store {
+  INTERNAL,  ///< stored inside FLUID app
+  USER,      ///< suite is stored in the user wide FLUID settings
+  PROJECT,   ///< suite is stored within the current .fl project file
+  FILE       ///< store suite in external file
+};
+
+
+class Project;
+
+class Application {
+  /// Currently selected project.
+  Project *current_project_ = new Project();
+  /// Working directory at application launch.
+  std::string launch_path_;
+  /// Path to store temporary files during app run.
+  std::string tmpdir_path;
+  /// True if the temporary file path was already created.
+  bool tmpdir_create_called = false;
+  // Generate a path to a directory for temporary data storage.
+  void create_tmpdir();
+  // Delete the temporary directory and all its contents.
+  void delete_tmpdir();
+
+public: // Member Variables
+  /// Application wide preferences
+  Fl_Preferences preferences;
+  /// Project history.
+  app::History history;
+  /// Command line arguments
+  app::Args args;
+  /// List of available layouts 
+  app::Layout_List layout_list;
+  /// Set, if Fluid runs in batch mode, and no user interface is activated.
+  int batch_mode { 0 };             // fluid + any code generators (-u, -c, -cs)
+
+  // TODO: make this into a class: app::Settings
+  /// Show guides in the design window when positioning widgets, saved in app preferences.
+  int show_guides { 1 };
+  /// Show areas of restricted use in overlay plane.
+  /// Restricted areas are widget that overlap each other, widgets that are outside
+  /// of their parent's bounds (except children of Scroll groups), and areas
+  /// within an Fl_Tile that are not covered by children.
+  int show_restricted { 1 };
+  /// Show a ghosted outline for groups that have very little contrast.
+  /// This makes groups with NO_BOX or FLAT_BOX better editable.
+  int show_ghosted_outline { 1 };
+  /// Show widget comments in the browser, saved in app preferences.
+  int show_comments { 1 };
+
+  // TODO: make this into a class: app::External_Editor
+  /// Use external editor for editing Code_Node, saved in app preferences.
+  int use_external_editor { 0 };
+  /// Debugging help for external Code_Node editor.
+  int debug_external_editor { 0 };
+  /// Run this command to load an Code_Node into an external editor, save in app preferences.
+  // TODO: make this into a std::string
+  char external_editor_command[512] { };
+
+  // TODO: make this into a class: app::GUI
+  Fl_Window *main_window { nullptr };
+  static Fl_Menu_Item main_menu[];
+  Fl_Menu_Bar *main_menubar { nullptr };
+  Fl_Menu_Item *save_item { nullptr };
+  Fl_Menu_Item *history_item { nullptr };
+  Fl_Menu_Item *widgetbin_item { nullptr };
+  Fl_Menu_Item *codeview_item { nullptr };
+  Fl_Menu_Item *overlay_item { nullptr };
+  Fl_Button *overlay_button { nullptr };
+  Fl_Menu_Item *guides_item { nullptr };
+  Fl_Menu_Item *restricted_item { nullptr };
+  /// Offset in pixels when adding widgets from an .fl file.
+  int pasteoffset { 0 };
+  int ipasteoffset { 0 };
+  /// FLUID-wide help dialog.
+  Fl_Help_Dialog *help_dialog { nullptr };
+
+public: // Methods
+  // Create the Fluid application.
+  Application();
+  /// Destructor.
+  ~Application() = default;
+  // Launch the application.
+  int run(int argc,char **argv);
+  // Quit the application and clean up.
+  void quit();
+  /// Quick access to the current project. Make sure it stays synched to current_project_.
+  Project &proj { *current_project_ };
+  // Return the working directory path at application launch.
+  const std::string &launch_path() const;
+  // Return the path to a temporary directory for this instance of Fluid.
+  const std::string &get_tmpdir();
+  // Return the path and filename of a temporary file for cut or duplicated data.
+  const char *cutfname(int which = 0);
+
+  // Clear the current project and create a new, empty one.
+  bool new_project(bool user_must_confirm = true);
+  // Open a file chooser and load an exiting project file.
+  bool open_project_file(const std::string &filename_arg);
+  // Load a project from the give file name and path.
+  bool merge_project_file(const std::string &filename_arg);
+  // Save the current design to the file given by \c filename.
+  void save_project_file(void *arg);
+  // Reload the file set by \c filename, replacing the current design.
+  void revert_project();
+  // Open the template browser and load a new file from templates.
+  bool new_project_from_template();
+  // Open the dialog to allow the user to print the current window.
+  void print_snapshots();
+  // Generate the C++ source and header filenames and write those files.
+  int write_code_files(bool dont_show_completion_dialog=false);
+
+  // User chose to cut the currently selected widgets.
+  void cut_selected();
+  // User chose to copy the currently selected widgets.
+  void copy_selected();
+  // User chose to paste the widgets from the cut buffer.
+  void paste_from_clipboard();
+  // Duplicate the selected widgets.
+  void duplicate_selected();
+  // User chose to delete the currently selected widgets.
+  void delete_selected();
+  // Show the editor for the \c current Node.
+  void edit_selected();
+  // User wants to sort selected widgets by y coordinate.
+  void sort_selected();
+  // Show or hide the widget bin.
+  void toggle_widget_bin();
+  // Open a dialog to show the HTML help page form the FLTK documentation folder.
+  void show_help(const char *name);
+  // Open the "About" dialog.
+  void about();
+
+  // Build the main app window and create a few other dialogs.
+  void make_main_window();
+  // Open a native file chooser to allow choosing a project file for reading.
+  std::string open_project_filechooser(const std::string &title);
+  // Give the user the opportunity to save a project before clearing it.
+  bool confirm_project_clear();
+  // Ensure that text widgets in the widget panel propagates apply current changes.
+  void flush_text_widgets();
+  // Position the given window window based on entries in the app preferences.
+  char position_window(Fl_Window *w, const char *prefsName, int Visible, int X, int Y, int W=0, int H=0);
+  // Save the position and visibility state of a window to the app preferences.
+  void save_position(Fl_Window *w, const char *prefsName);
+  // Change the app's and hence preview the design's scheme.
+  void set_scheme(const char *new_scheme);
+  // Read Fluid's scheme preferences and set the app's scheme.
+  void init_scheme();
+
+#ifdef __APPLE__
+  static void apple_open_cb(const char *c);
+#endif // __APPLE__
+};
+
+} // namespace fld
+
+extern fld::Application Fluid;
+
+
+#endif // FLUID_FLUID_H
+