Menu Widgets

Menu bars, popup menus, and choice widgets for hierarchical options

FLTK provides several menu widgets for presenting hierarchical options to users. All menu widgets use Fl_Menu_Item arrays to define menu structure.

Fl_Menu_Bar

Header: FL/Fl_Menu_Bar.H

A horizontal menu bar typically placed at the top of a window, similar to standard application menus.

Constructor

Fl_Menu_Bar(int x, int y, int w, int h, const char *label = 0);

Parameters:

• Typically positioned at (0, 0) with width matching window
• Height should be around 30 pixels for default font
• Label usually not used (set to 0)

Key Methods

add() - Add Menu Items

Add items to the menu using path notation.

Fl_Menu_Bar *menu = new Fl_Menu_Bar(0, 0, 400, 30);

// Simple items
menu->add("File/New");
menu->add("File/Open");
menu->add("File/Save");
menu->add("File/Quit");

// With callbacks
menu->add("File/Save", FL_CTRL+'s', save_cb);
menu->add("Edit/Copy", FL_CTRL+'c', copy_cb);

// Submenus
menu->add("Edit/Find/Find Next");
menu->add("Edit/Find/Replace");

// Separator
menu->add("File/Recent Files", 0, 0, 0, FL_MENU_DIVIDER);

value() - Get Selected Item

Returns the last menu item picked by the user.

const Fl_Menu_Item* value() const;
int value(int index);
int value(const Fl_Menu_Item *item);

const Fl_Menu_Item *item = menu->value();
if (item) {
  printf("Selected: %s\n", item->label());
}

find_item() - Locate Menu Item

Find a menu item by its label path.

Fl_Menu_Item *item = (Fl_Menu_Item*)menu->find_item("File/Save");
if (item) {
  item->deactivate();  // Disable Save option
}

mode() - Item Flags

Get or set menu item flags (checkmarks, radio buttons, inactive, etc.).

// Set checkmark
menu->mode(menu->find_index("View/Show Grid"), FL_MENU_TOGGLE);

// Check if item is checked
if (menu->mode(idx) & FL_MENU_VALUE) {
  printf("Item is checked\n");
}

Example from Source

#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/Fl_Menu_Bar.H>
#include <FL/fl_ask.H>

void menu_cb(Fl_Widget *w, void *) {
  Fl_Menu_Bar *menu = (Fl_Menu_Bar*)w;
  const Fl_Menu_Item *item = menu->mvalue();
  if (!item) return;
  
  printf("Menu: %s\n", item->label());
  
  if (strcmp(item->label(), "Quit") == 0) {
    exit(0);
  }
}

int main() {
  Fl_Window *win = new Fl_Window(400, 300, "Menu Example");
  
  Fl_Menu_Bar *menubar = new Fl_Menu_Bar(0, 0, 400, 30);
  menubar->add("File/New",   FL_CTRL+'n', menu_cb);
  menubar->add("File/Open",  FL_CTRL+'o', menu_cb);
  menubar->add("File/Save",  FL_CTRL+'s', menu_cb);
  menubar->add("File/Quit",  FL_CTRL+'q', menu_cb);
  menubar->add("Edit/Cut",   FL_CTRL+'x', menu_cb);
  menubar->add("Edit/Copy",  FL_CTRL+'c', menu_cb);
  menubar->add("Edit/Paste", FL_CTRL+'v', menu_cb);
  menubar->add("Help/About", 0, menu_cb);
  
  win->end();
  win->show();
  return Fl::run();
}

Visual Description

A Fl_Menu_Bar appears as a horizontal strip with top-level menu labels. Clicking a label drops down a vertical menu. Submenus appear to the right of parent items. Active items highlight on hover.

Fl_Menu_Button

Header: FL/Fl_Menu_Button.H

A button that pops up a menu when clicked. Useful for context menus and toolbar dropdowns.

Fl_Menu_Button *popup = new Fl_Menu_Button(100, 50, 100, 30, "Options");
popup->add("Copy");
popup->add("Paste");
popup->add("Delete");

// Right-click popup menu
popup->type(Fl_Menu_Button::POPUP3);  // Pops up on right-click

Fl_Choice

Header: FL/Fl_Choice.H

A button that pops up a menu (similar to HTML <select>). Shows the currently selected item on the button face.

Constructor

Fl_Choice(int x, int y, int w, int h, const char *label = 0);

Example

Fl_Choice *choice = new Fl_Choice(100, 50, 150, 30, "Size:");
choice->add("Small");
choice->add("Medium");
choice->add("Large");
choice->add("Extra Large");
choice->value(1);  // Select "Medium" (zero-based index)

choice->callback([](Fl_Widget *w, void *) {
  Fl_Choice *ch = (Fl_Choice*)w;
  printf("Selected: %s (index %d)\n", ch->text(), ch->value());
});

Visual Description

Displays as a button showing the current selection with a small down-arrow indicator. Clicking opens a vertical menu of options.

Menu Item Flags

Menu items can have various flags set:

FL_MENU_INACTIVE    // Grayed out, cannot select
FL_MENU_TOGGLE      // Checkbox item (can be on/off)
FL_MENU_VALUE       // Currently checked (for toggle items)
FL_MENU_RADIO       // Radio button (one of group)
FL_MENU_INVISIBLE   // Item not displayed
FL_MENU_DIVIDER     // Horizontal separator after item
FL_SUBMENU          // Item has submenu
FL_SUBMENU_POINTER  // Submenu is pointer not array

Using Flags

// Add checkbox menu item
menu->add("View/Show Toolbar", 0, toggle_cb, 0, FL_MENU_TOGGLE);

// Add radio button group
menu->add("Format/Left",   0, align_cb, (void*)0, FL_MENU_RADIO);
menu->add("Format/Center", 0, align_cb, (void*)1, FL_MENU_RADIO);
menu->add("Format/Right",  0, align_cb, (void*)2, FL_MENU_RADIO);
menu->set_only(menu->find_item("Format/Left"));  // Select one

// Add separator
menu->add("File/Recent", 0, 0, 0, FL_MENU_DIVIDER);

Menu Widget Gallery

Menu Bar

Fl_Menu_Bar - Application menu

Horizontal bar with top-level items. Clicking opens drop-down submenus.

Use for: Main application menus (File, Edit, View, etc.)

Menu Button

Fl_Menu_Button - Popup menu

Button that shows menu when clicked. Can be left, middle, or right-click.

Use for: Context menus, more options, toolbar dropdowns

Choice Widget

Fl_Choice - Dropdown selector

Shows current selection on button. Opens menu to change selection.

Use for: Option pickers, single selection from list

Submenu

Submenu Items - Nested menus

Menu items with arrows indicating deeper levels.

Use for: Organizing related commands hierarchically

Common Patterns

Application Menu Bar

Fl_Menu_Bar *menubar = new Fl_Menu_Bar(0, 0, win->w(), 30);

// File menu
menubar->add("&File/&New",        FL_CTRL+'n', new_cb);
menubar->add("&File/&Open...",    FL_CTRL+'o', open_cb);
menubar->add("&File/&Save",       FL_CTRL+'s', save_cb);
menubar->add("&File/Save &As...", FL_CTRL+FL_SHIFT+'s', saveas_cb);
menubar->add("&File/_", 0, 0, 0, FL_MENU_DIVIDER);  // Separator
menubar->add("&File/&Quit",       FL_CTRL+'q', quit_cb);

// Edit menu
menubar->add("&Edit/&Undo",   FL_CTRL+'z', undo_cb);
menubar->add("&Edit/&Cut",    FL_CTRL+'x', cut_cb);
menubar->add("&Edit/C&opy",   FL_CTRL+'c', copy_cb);
menubar->add("&Edit/&Paste",  FL_CTRL+'v', paste_cb);

// View menu with checkboxes
menubar->add("&View/&Toolbar", 0, toggle_cb, (void*)0, FL_MENU_TOGGLE|FL_MENU_VALUE);
menubar->add("&View/&Statusbar", 0, toggle_cb, (void*)1, FL_MENU_TOGGLE|FL_MENU_VALUE);

Context Menu

class MyWidget : public Fl_Widget {
  Fl_Menu_Button *context_menu;
  
public:
  MyWidget(int x, int y, int w, int h) : Fl_Widget(x, y, w, h) {
    context_menu = new Fl_Menu_Button(0, 0, 0, 0);
    context_menu->type(Fl_Menu_Button::POPUP3);
    context_menu->add("Cut", 0, cut_cb, this);
    context_menu->add("Copy", 0, copy_cb, this);
    context_menu->add("Paste", 0, paste_cb, this);
  }
  
  int handle(int event) {
    if (event == FL_PUSH && Fl::event_button() == FL_RIGHT_MOUSE) {
      const Fl_Menu_Item *m = context_menu->popup(Fl::event_x(), Fl::event_y());
      if (m) m->do_callback(this, m->user_data());
      return 1;
    }
    return Fl_Widget::handle(event);
  }
};

Dynamic Menu Updates

void update_recent_files(Fl_Menu_Bar *menu) {
  // Remove old recent files
  int idx = menu->find_index("File/Recent Files");
  while (menu->text(idx+1) && strstr(menu->text(idx+1), "Recent")) {
    menu->remove(idx+1);
  }
  
  // Add new recent files
  for (auto &file : recent_files) {
    menu->insert(idx+1, file.c_str(), 0, open_recent_cb);
  }
}

Choice with Callback

Fl_Choice *language = new Fl_Choice(100, 50, 150, 30, "Language:");
language->add("English");
language->add("Español");
language->add("Français");
language->add("Deutsch");
language->value(0);

language->callback([](Fl_Widget *w, void *) {
  Fl_Choice *ch = (Fl_Choice*)w;
  switch(ch->value()) {
    case 0: set_locale("en"); break;
    case 1: set_locale("es"); break;
    case 2: set_locale("fr"); break;
    case 3: set_locale("de"); break;
  }
});

Shortcuts and Accelerators

// Keyboard shortcuts
menu->add("File/Save", FL_CTRL + 's', save_cb);
menu->add("File/Print", FL_CTRL + 'p', print_cb);
menu->add("Help", FL_F + 1, help_cb);  // F1 key

// Alt+key shortcuts using & in label
menu->add("&File/&New");   // Alt+F opens File, Alt+N triggers New
menu->add("&Edit/&Copy");  // Alt+E opens Edit, Alt+C triggers Copy

Important Notes

Menu items in an Fl_Menu_Bar are stored in a single array. Inserting or removing items invalidates any stored pointers to menu items.

The ’&’ character in menu labels creates Alt+key shortcuts and underlines the following character on Windows/Linux. It’s ignored on macOS.

Use the FL_BEFORE_MENU event to update menu item states (enable/disable, check/uncheck) just before the menu displays. See test/menubar.cxx for examples.

Reference

• Source: FL/Fl_Menu_Bar.H (lines 25-106)
• Source: FL/Fl_Menu_Button.H
• Source: FL/Fl_Choice.H (lines 25-128)
• Example: test/menubar.cxx