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, 142 insertions, 0 deletions

diff --git a/fluid/io/String_Writer.cxx b/fluid/io/String_Writer.cxx
new file mode 100644
index 000000000..6b70ec1f3
--- /dev/null
+++ b/fluid/io/String_Writer.cxx
@@ -0,0 +1,142 @@
+//
+// String File Writer 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 "io/String_Writer.h"
+
+#include "Fluid.h"
+#include "Project.h"
+#include "nodes/Window_Node.h"
+#include "nodes/Function_Node.h"
+
+using namespace fld;
+using namespace fld::io;
+
+/**
+ Write a string to a file, replacing all non-ASCII characters with octal codes.
+ \param[in] out output file
+ \param[in] text write this NUL terminated utf-8 string
+ \return EOF if any of the file access calls failed, 0 if OK
+ */
+static int write_escaped_strings(FILE *out, const char *text) {
+  int ret = 0;
+  const unsigned char *utf8_text = (const unsigned char *)text;
+  for (const unsigned char *s = utf8_text; *s; ++s) {
+    unsigned char c = *s;
+    // escape control characters, delete, all utf-8, and the double quotes
+    // note: we should have an option in the project settings to allow utf-8
+    //       characters in the output text and not escape them
+    if (c < 32 || c > 126 || c == '\"') {
+      if (c == '\r') {
+        ret = fputs("\\r", out);
+      } else if (c == '\n') {
+        ret = fputs("\\n", out);
+      } else {
+        ret = fprintf(out, "\\%03o", c);
+      }
+    } else {
+      ret = putc((int)c, out);
+    }
+  }
+  return ret;
+}
+
+/**
+ Write a file that contains all label and tooltip strings for internationalization.
+ The user is responsible to set the right file name extension. The file format
+ is determined by `proj_.i18n_type`.
+ \param[in] filename file path and name to a file that will hold the strings
+ \return 1 if the file could not be opened for writing, or the result of `fclose`.
+ */
+int fld::io::write_strings(Project &proj, const std::string &filename) {
+  Node *p;
+  Widget_Node *w;
+  int i;
+
+  FILE *fp = fl_fopen(filename.c_str(), "wb");
+  if (!fp) return 1;
+
+  switch (proj.i18n_type) {
+    case fld::I18n_Type::NONE : /* None, just put static text out */
+      fprintf(fp, "# generated by Fast Light User Interface Designer (fluid) version %.4f\n",
+              FL_VERSION);
+      for (auto w: proj.tree.all_widgets()) {
+        if (w->label()) {
+          write_escaped_strings(fp, w->label());
+          putc('\n', fp);
+        }
+        if (w->tooltip()) {
+          write_escaped_strings(fp, w->tooltip());
+          putc('\n', fp);
+        }
+      }
+      break;
+    case fld::I18n_Type::GNU : /* GNU gettext, put a .po file out */
+      fprintf(fp, "# generated by Fast Light User Interface Designer (fluid) version %.4f\n",
+              FL_VERSION);
+      for (p = proj.tree.first; p; p = p->next) {
+        if (p->is_widget()) {
+          w = (Widget_Node *)p;
+
+          if (w->label()) {
+            fputs("msgid \"", fp);
+            write_escaped_strings(fp, w->label());
+            fputs("\"\n", fp);
+
+            fputs("msgstr \"", fp);
+            write_escaped_strings(fp, w->label());
+            fputs("\"\n", fp);
+          }
+
+          if (w->tooltip()) {
+            fputs("msgid \"", fp);
+            write_escaped_strings(fp, w->tooltip());
+            fputs("\"\n", fp);
+
+            fputs("msgstr \"", fp);
+            write_escaped_strings(fp, w->tooltip());
+            fputs("\"\n", fp);
+          }
+        }
+      }
+      break;
+    case fld::I18n_Type::POSIX : /* POSIX catgets, put a .msg file out */
+      fprintf(fp, "$ generated by Fast Light User Interface Designer (fluid) version %.4f\n",
+              FL_VERSION);
+      fprintf(fp, "$set %s\n", proj.i18n_pos_set.c_str());
+      fputs("$quote \"\n", fp);
+
+      for (i = 1, p = proj.tree.first; p; p = p->next) {
+        if (p->is_widget()) {
+          w = (Widget_Node *)p;
+
+          if (w->label()) {
+            fprintf(fp, "%d \"", i ++);
+            write_escaped_strings(fp, w->label());
+            fputs("\"\n", fp);
+          }
+
+          if (w->tooltip()) {
+            fprintf(fp, "%d \"", i ++);
+            write_escaped_strings(fp, w->tooltip());
+            fputs("\"\n", fp);
+          }
+        }
+      }
+      break;
+  }
+
+  return fclose(fp);
+}