Fl_Group: convert array of children to std::vector

Note: this is only a hidden implementation detail: all concerned
variables are private, and the code is simplified (less error prone).

Size of Fl_Group on 64-bit Linux: 168 -> 176 Bytes (+8 Bytes).

test/group.cxx: test for Fl_Group::{add, insert, remove} etc.

2 files changed, 149 insertions, 0 deletions

diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index eff372154..d2e1c9c5f 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -116,6 +116,7 @@ fl_create_example(grid_alignment grid_alignment.cxx fltk::fltk)
 fl_create_example(grid_buttons grid_buttons.cxx fltk::fltk)
 fl_create_example(grid_dialog grid_dialog.cxx fltk::fltk)
 fl_create_example(grid_login grid_login.cxx fltk::fltk)
+fl_create_example(group group.cxx fltk::fltk)
 fl_create_example(handle_events handle_events.cxx "${GLDEMO_LIBS}")
 fl_create_example(handle_keys handle_keys.cxx fltk::fltk)
 fl_create_example(hello hello.cxx fltk::fltk)
diff --git a/test/group.cxx b/test/group.cxx
new file mode 100644
index 000000000..2e661f560
--- /dev/null
+++ b/test/group.cxx
@@ -0,0 +1,148 @@
+//
+// Fl_Group manipulation test program for the Fast Light Tool Kit (FLTK).
+//
+// Copyright 2024 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
+//
+
+// This test program creates two groups and moves widgets around
+// between groups to test insert, append, remove, etc..
+
+#include <FL/Fl_Double_Window.H>
+#include <FL/Fl_Box.H>
+#include <FL/Fl_Button.H>
+#include <FL/Fl_Flex.H>
+#include <FL/Fl_Terminal.H>
+
+// #include <vector>
+
+// Globals for easier testing
+
+const int ww = 520; // window width
+const int wh = 200; // window height (w/o button and terminal)
+const int th = 200; // initial terminal (tty) height
+
+Fl_Double_Window *window;
+Fl_Flex *g1, *g2;
+Fl_Box *b1, *b2, *b3, *b4;
+Fl_Terminal *tty;
+
+void debug_group(Fl_Group *g) {
+  const int nc = g->children();
+  tty->printf("%s has %2d child%s\n", g->label(), nc, nc == 1 ? "" : "ren");
+  for (int i = 0; i < g->children(); i++) {
+    Fl_Widget *w = g->child(i);
+    const char *lbl = w ? w->label() : "";
+#if (0) // full info with child address
+    tty->printf("    Child[%2d] (%p) = %s\n", i, (void *)w, lbl);
+#else // short info
+    tty->printf("    Child[%2d] = %s\n", i, lbl);
+#endif
+  }
+}
+
+// This button callback exercises multiple Fl_Group operations in a circle.
+// Note to devs: make sure that the last action restores the original layout.
+
+void button_cb(Fl_Widget *, void *) {
+  static int move = 0;
+  move++;
+  tty->printf("\nMove %2d:\n", move);
+  switch(move) {
+    case  1: g1->insert(*b3, 0);    break;
+    case  2: g1->insert(*b3, 2);    break;
+    case  3: g1->insert(*b2, 1);    break;
+    case  4: g1->insert(*b1, 5);    break;
+    case  5: g1->insert(*b1, 1);    break;
+    case  6: g1->insert(*b4, 3);    break;
+    case  7: g1->insert(*b3, 2);    break; // no-op (same position)
+    case  8: g2->add(b3);           break;
+    case  9: g2->add(b3);           break; // no-op (same position)
+    case 10: g2->add(b4);           break;
+    case 11: g1->remove(b2);        break;
+    case 12: g1->add(b2); move = 0; break; // last move: reset counter
+    default:              move = 0; break; // safety: reset counter
+  }
+  debug_group(g1);
+  debug_group(g2);
+  g1->layout();
+  g2->layout();
+  window->redraw();
+}
+
+int main(int argc, char **argv) {
+  window = new Fl_Double_Window(ww, wh + th + 100, "Fl_Group Test");
+
+  g1 = new Fl_Flex(50, 20, ww - 80, wh / 2 - 20, "g1: ");
+  g1->type(Fl_Flex::HORIZONTAL);
+  g1->box(FL_FLAT_BOX);
+  g1->color(FL_WHITE);
+  g1->align(FL_ALIGN_LEFT);
+
+  b1 = new Fl_Box(0, 0, 0, 0, "b1");
+  b1->box(FL_FLAT_BOX);
+  b1->color(FL_RED);
+
+  b2 = new Fl_Box(0, 0, 0, 0, "b2");
+  b2->box(FL_FLAT_BOX);
+  b2->color(FL_GREEN);
+
+  g1->end();
+
+  g2 = new Fl_Flex(50, wh / 2 + 20, ww - 80, wh / 2 - 20, "g2: ");
+  g2->type(Fl_Flex::HORIZONTAL);
+  g2->box(FL_FLAT_BOX);
+  g2->color(FL_WHITE);
+  g2->align(FL_ALIGN_LEFT);
+
+  b3 = new Fl_Box(0, 0, 0, 0, "b3");
+  b3->box(FL_FLAT_BOX);
+  b3->color(FL_BLUE);
+  b3->labelcolor(FL_WHITE);
+
+  b4 = new Fl_Box(0, 0, 0, 0, "b4");
+  b4->box(FL_FLAT_BOX);
+  b4->color(FL_YELLOW);
+
+  g2->end();
+
+  auto bt = new Fl_Button(10, wh + 20, ww - 20, 40, "Move children ...");
+  bt->callback(button_cb);
+
+  tty = new Fl_Terminal(10, wh + 80, ww - 20, th);
+
+  window->end();
+  window->resizable(tty);
+  window->size_range(window->w(), window->h());
+  window->show(argc, argv);
+
+  tty->printf("sizeof(Fl_Widget)    = %3d\n", (int)sizeof(Fl_Widget));
+  tty->printf("sizeof(Fl_Box)       = %3d\n", (int)sizeof(Fl_Box));
+  tty->printf("sizeof(Fl_Button)    = %3d\n", (int)sizeof(Fl_Button));
+  tty->printf("sizeof(Fl_Group)     = %3d\n", (int)sizeof(Fl_Group));
+  tty->printf("sizeof(Fl_Window)    = %3d\n", (int)sizeof(Fl_Window));
+
+  int idx = g2->children() + 3;
+  tty->printf("child(n) out of range: g2->child(%d) = %p, children = %d\n",
+              idx, (void *)g2->child(idx), g2->children());
+
+  int ret = Fl::run();
+
+  // reset pointers to give memory checkers a chance to test for leaks
+  g1 = g2 = nullptr;
+  tty = nullptr;
+  b1 = b2 = b3 = b4 = nullptr;
+  bt = nullptr;
+  delete window;
+
+  return ret;
+}