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, 128 insertions, 0 deletions

diff --git a/fluid/nodes/Tree.cxx b/fluid/nodes/Tree.cxx
new file mode 100644
index 000000000..ca9b3d761
--- /dev/null
+++ b/fluid/nodes/Tree.cxx
@@ -0,0 +1,128 @@
+//
+// Node Tree code 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
+//
+
+
+#include "nodes/Tree.h"
+
+#include "Project.h"
+
+using namespace fld;
+using namespace fld::node;
+
+
+Tree::Iterator::Iterator(Node *t, bool only_selected)
+: type_(t)
+, only_selected_(only_selected)
+{
+  if (t) {
+    if (only_selected_) {
+      if (!type_->selected) {
+        operator++();
+      }
+    }
+  }
+}
+
+Tree::Iterator &Tree::Iterator::operator++() {
+  if (only_selected_) {
+    do {
+      type_ = type_->next;
+    } while (type_ && !type_->selected);
+  } else {
+    type_ = type_->next;
+  }
+  return *this;
+}
+
+Tree::WIterator::WIterator(Node *t, bool only_selected)
+: type_(t)
+, only_selected_(only_selected)
+{
+  if (t) {
+    if (only_selected_) {
+      if (!type_->selected || !type_->is_widget()) {
+        operator++();
+      }
+    } else {
+      if (!type_->is_widget()) {
+        operator++();
+      }
+    }
+  }
+}
+
+Tree::WIterator& Tree::WIterator::operator++() {
+  if (only_selected_) {
+    do {
+      type_ = type_->next;
+    } while (type_ && (!type_->selected || !type_->is_widget()));
+  } else {
+    do {
+      type_ = type_->next;
+    } while (type_ && !type_->is_widget());
+  }
+  return *this;
+}
+
+
+Tree::Tree(Project &proj)
+: proj_(proj)
+{ (void)proj_; }
+
+
+/** Find a node by its unique id.
+
+ Every node in a type tree has an id that is unique for the current project.
+ Walk the tree and return the node with this uid.
+
+ \param[in] uid any number between 0 and 65535
+ \return the node with this uid, or nullptr if not found
+ */
+Node *Tree::find_by_uid(unsigned short uid) {
+  for (auto tp: all_nodes()) {
+    if (tp->get_uid() == uid) return tp;
+  }
+  return nullptr;
+}
+
+
+/** Find a type node by using the codeview text positions.
+
+ \param[in] text_type 0=source file, 1=header, 2=.fl project file
+ \param[in] crsr cursor position in text
+ \return the node we found or nullptr
+ */
+Node *Tree::find_in_text(int text_type, int crsr) {
+  for (auto node: all_nodes()) {
+    switch (text_type) {
+      case 0:
+        if (crsr >= node->code1_start && crsr < node->code1_end) return node;
+        if (crsr >= node->code2_start && crsr < node->code2_end) return node;
+        if (crsr >= node->code_static_start && crsr < node->code_static_end) return node;
+        break;
+      case 1:
+        if (crsr >= node->header1_start && crsr < node->header1_end) return node;
+        if (crsr >= node->header2_start && crsr < node->header2_end) return node;
+        if (crsr >= node->header_static_start && crsr < node->header_static_end) return node;
+        break;
+      case 2:
+        if (crsr >= node->proj1_start && crsr < node->proj1_end) return node;
+        if (crsr >= node->proj2_start && crsr < node->proj2_end) return node;
+        break;
+    }
+  }
+  return nullptr;
+}