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C - FLTK Enumerations

This appendix lists the enumerations provided in the <FL/Enumerations.H> header file, organized by section. Constants whose value is zero are marked with "(0)", this is often useful to know when programming.

Version Numbers

The FLTK version number is stored in a number of compile-time constants:
  • FL_MAJOR_VERSION - The major release number, currently 1.
  • FL_MINOR_VERSION - The minor release number, currently 1.
  • FL_PATCH_VERSION - The patch release number, currently 0.
  • FL_VERSION - A combined floating-point version number for the major, minor, and patch release numbers, currently 1.0100.


Events are identified by an Fl_Event enumeration value. The following events are currently defined:
  • FL_NO_EVENT - No event (or an event fltk does not understand) occurred (0).
  • FL_PUSH - A mouse button was pushed.
  • FL_RELEASE - A mouse button was released.
  • FL_ENTER - The mouse pointer entered a widget.
  • FL_LEAVE - The mouse pointer left a widget.
  • FL_DRAG - The mouse pointer was moved with a button pressed.
  • FL_FOCUS - A widget should receive keyboard focus.
  • FL_UNFOCUS - A widget loses keyboard focus.
  • FL_KEYBOARD - A key was pressed.
  • FL_CLOSE - A window was closed.
  • FL_MOVE - The mouse pointer was moved with no buttons pressed.
  • FL_SHORTCUT - The user pressed a shortcut key.
  • FL_DEACTIVATE - The widget has been deactivated.
  • FL_ACTIVATE - The widget has been activated.
  • FL_HIDE - The widget has been hidden.
  • FL_SHOW - The widget has been shown.
  • FL_PASTE - The widget should paste the contents of the clipboard.
  • FL_SELECTIONCLEAR - The widget should clear any selections made for the clipboard.
  • FL_MOUSEWHEEL - The horizontal or vertical mousewheel was turned.
  • FL_DND_ENTER - The mouse pointer entered a widget dragging data.
  • FL_DND_DRAG - The mouse pointer was moved dragging data.
  • FL_DND_LEAVE - The mouse pointer left a widget still dragging data.
  • FL_DND_RELEASE - Dragged data is about to be dropped.

Callback "When" Conditions

The following constants determine when a callback is performed:
  • FL_WHEN_NEVER - Never call the callback (0).
  • FL_WHEN_CHANGED - Do the callback only when the widget value changes.
  • FL_WHEN_NOT_CHANGED - Do the callback whenever the user interacts with the widget.
  • FL_WHEN_RELEASE - Do the callback when the button or key is released and the value changes.
  • FL_WHEN_ENTER_KEY - Do the callback when the user presses the ENTER key and the value changes.
  • FL_WHEN_RELEASE_ALWAYS - Do the callback when the button or key is released, even if the value doesn't change.
  • FL_WHEN_ENTER_KEY_ALWAYS - Do the callback when the user presses the ENTER key, even if the value doesn't change.

Fl::event_button() Values

The following constants define the button numbers for FL_PUSH and FL_RELEASE events:

  • FL_LEFT_MOUSE - the left mouse button
  • FL_MIDDLE_MOUSE - the middle mouse button
  • FL_RIGHT_MOUSE - the right mouse button

Fl::event_key() Values

The following constants define the non-ASCII keys on the keyboard for FL_KEYBOARD and FL_SHORTCUT events:
  • FL_Button - A mouse button; use Fl_Button + n for mouse button n.
  • FL_BackSpace - The backspace key.
  • FL_Tab - The tab key.
  • FL_Enter - The enter key.
  • FL_Pause - The pause key.
  • FL_Scroll_Lock - The scroll lock key.
  • FL_Escape - The escape key.
  • FL_Home - The home key.
  • FL_Left - The left arrow key.
  • FL_Up - The up arrow key.
  • FL_Right - The right arrow key.
  • FL_Down - The down arrow key.
  • FL_Page_Up - The page-up key.
  • FL_Page_Down - The page-down key.
  • FL_End - The end key.
  • FL_Print - The print (or print-screen) key.
  • FL_Insert - The insert key.
  • FL_Menu - The menu key.
  • FL_Num_Lock - The num lock key.
  • FL_KP - One of the keypad numbers; use FL_KP + n for number n.
  • FL_KP_Enter - The enter key on the keypad.
  • FL_F - One of the function keys; use FL_F + n for function key n.
  • FL_Shift_L - The lefthand shift key.
  • FL_Shift_R - The righthand shift key.
  • FL_Control_L - The lefthand control key.
  • FL_Control_R - The righthand control key.
  • FL_Caps_Lock - The caps lock key.
  • FL_Meta_L - The left meta/Windows key.
  • FL_Meta_R - The right meta/Windows key.
  • FL_Alt_L - The left alt key.
  • FL_Alt_R - The right alt key.
  • FL_Delete - The delete key.

Fl::event_state() Values

The following constants define bits in the Fl::event_state() value:
  • FL_SHIFT - One of the shift keys is down.
  • FL_CAPS_LOCK - The caps lock is on.
  • FL_CTRL - One of the ctrl keys is down.
  • FL_ALT - One of the alt keys is down.
  • FL_NUM_LOCK - The num lock is on.
  • FL_META - One of the meta/Windows keys is down.
  • FL_COMMAND - An alias for FL_CTRL on WIN32 and X11, or FL_META on MacOS X.
  • FL_SCROLL_LOCK - The scroll lock is on.
  • FL_BUTTON1 - Mouse button 1 is pushed.
  • FL_BUTTON2 - Mouse button 2 is pushed.
  • FL_BUTTON3 - Mouse button 3 is pushed.
  • FL_BUTTONS - Any mouse button is pushed.
  • FL_BUTTON(n) - Mouse button N (N > 0) is pushed.

Alignment Values

The following constants define bits that can be used with Fl_Widget::align() to control the positioning of the label:
  • FL_ALIGN_CENTER - The label is centered (0).
  • FL_ALIGN_TOP - The label is top-aligned.
  • FL_ALIGN_BOTTOM - The label is bottom-aligned.
  • FL_ALIGN_LEFT - The label is left-aligned.
  • FL_ALIGN_RIGHT - The label is right-aligned.
  • FL_ALIGN_CLIP - The label is clipped to the widget.
  • FL_ALIGN_WRAP - The label text is wrapped as needed.
  • FL_ALIGN_INSIDE - 'or' this with other values to put label inside the widget.


The following constants define the standard FLTK fonts:
  • FL_HELVETICA - Helvetica (or Arial) normal (0).
  • FL_HELVETICA_BOLD - Helvetica (or Arial) bold.
  • FL_HELVETICA_ITALIC - Helvetica (or Arial) oblique.
  • FL_HELVETICA_BOLD_ITALIC - Helvetica (or Arial) bold-oblique.
  • FL_COURIER - Courier normal.
  • FL_COURIER_BOLD - Courier bold.
  • FL_COURIER_ITALIC - Courier italic.
  • FL_COURIER_BOLD_ITALIC - Courier bold-italic.
  • FL_TIMES - Times roman.
  • FL_TIMES_BOLD - Times bold.
  • FL_TIMES_ITALIC - Times italic.
  • FL_TIMES_BOLD_ITALIC - Times bold-italic.
  • FL_SYMBOL - Standard symbol font.
  • FL_SCREEN - Default monospaced screen font.
  • FL_SCREEN_BOLD - Default monospaced bold screen font.
  • FL_ZAPF_DINGBATS - Zapf-dingbats font.


The Fl_Color enumeration type holds a FLTK color value. Colors are either 8-bit indexes into a virtual colormap or 24-bit RGB color values. Color indices occupy the lower 8 bits of the value, while RGB colors occupy the upper 24 bits, for a byte organization of RGBI.

Color Constants

Constants are defined for the user-defined foreground and background colors, as well as specific colors and the start of the grayscale ramp and color cube in the virtual colormap. Inline functions are provided to retrieve specific grayscale, color cube, or RGB color values.

The following color constants can be used to access the user-defined colors:

  • FL_BACKGROUND_COLOR - the default background color
  • FL_BACKGROUND2_COLOR - the default background color for text, list, and valuator widgets
  • FL_FOREGROUND_COLOR - the default foreground color (0) used for labels and text
  • FL_INACTIVE_COLOR - the inactive foreground color
  • FL_SELECTION_COLOR - the default selection/highlight color

The following color constants can be used to access the colors from the FLTK standard color cube:

  • FL_RED

The inline methods for getting a grayscale, color cube, or RGB color value are described in Appendix B - Function Reference.


The following constants define the mouse cursors that are available in FLTK. The double-headed arrows are bitmaps provided by FLTK on X, the others are provided by system-defined cursors.

  • FL_CURSOR_DEFAULT - the default cursor, usually an arrow (0)
  • FL_CURSOR_ARROW - an arrow pointer
  • FL_CURSOR_CROSS - crosshair
  • FL_CURSOR_WAIT - watch or hourglass
  • FL_CURSOR_HAND - hand (uparrow on MSWindows)
  • FL_CURSOR_HELP - question mark
  • FL_CURSOR_MOVE - 4-pointed arrow
  • FL_CURSOR_NS - up/down arrow
  • FL_CURSOR_WE - left/right arrow
  • FL_CURSOR_NWSE - diagonal arrow
  • FL_CURSOR_NESW - diagonal arrow
  • FL_CURSOR_NONE - invisible

FD "When" Conditions

  • FL_READ - Call the callback when there is data to be read.
  • FL_WRITE - Call the callback when data can be written without blocking.
  • FL_EXCEPT - Call the callback if an exception occurs on the file.

Damage Masks

The following damage mask bits are used by the standard FLTK widgets:
  • FL_DAMAGE_CHILD - A child needs to be redrawn.
  • FL_DAMAGE_EXPOSE - The window was exposed.
  • FL_DAMAGE_SCROLL - The Fl_Scroll widget was scrolled.
  • FL_DAMAGE_OVERLAY - The overlay planes need to be redrawn.
  • FL_DAMAGE_USER1 - First user-defined damage bit.
  • FL_DAMAGE_USER2 - Second user-defined damage bit.
  • FL_DAMAGE_ALL - Everything needs to be redrawn.

User Comments [ Add Comment ]

From Anonymous, 12:48 Oct 13, 2004 (score=1)

The list of events above includes:
  FL_KEYBOARD - A key was pressed.

But according to the enumerations.H file, there is an FL_KEYDOWN event and an FL_KEYUP event, but no FL_KEYBOARD event.
Reply ]

From greg.ercolano, 15:12 Jul 30, 2009 (score=3)

There should indeed be some clarification on the FL_KEYBOARD event.

It's not described in the "Handling Events" chapter, though its referenced several times.

FL_KEYBOARD is equivalent to FL_KEYDOWN. Not sure why there are two names for the same event.
Reply ]


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