Class Widget

The base class for all FLTK widgets.

Subclasses: Box Browser_ Button Group Input_ Menu_

Property index

active	changed	labelfont	selection_color	when
align	color	labelsize	takesevents	window
argument	h	labeltype	type	x
box	label	output	visible	y
callback	labelcolor	parent	w

Function index

activate	clear_output	inside	resize	size
active_r	contains	position	set_changed	take_focus
clear_changed	deactivate	redraw	set_output	visible_r

Key properties

type	name	summary
string	label	Widget label
integer	labelsize	Label font size
Font	labelfont	Label font
Color	labelcolor	Label color
Color	color	Color of widget
Boxtype	box	Border and style of widget
Align	align	Position of label
function	callback	Function called when triggered

Key functions

type	name	summary
void	redraw()	Redraw the widget
void	resize(integer x, integer y, integer w, integer h)	Change this widget's position and size
boolean	take_focus()	Give this widget the focus

Description

Widget is the base class for all widgets in FLTK. You can't create one of these directly, but all other widgets inherit from it.

When you create any widget, it's added to the current Group (which may be a Window. See the Group documentation for more information on groups.

When you change properties that affect the widget's appearance (like color or label), it's up to you to call redraw() to update the display.

Detailed reference

parent: Widget

Returns a the parent widget. Usually this is a Group or Window. Returns nil if none. parent is not readonly, but you should not set it unless you really know what you're doing.

The box property identifies a routine that draws the border and background of the widget. For instance, a Button with a raised border has Boxtype.up; a Button with lowered border has Boxtype.down.

See Boxtype for the available types. The default depends on the widget, but is usually Boxtype.none or Boxtype.up.

color: Color

This color is passed to the box routine; it's usually the overall color of the widget

color is an index into an internal table of rgb colors. For most widgets this defaults to Color.gray. See the documentation of Color for named colors and operations that affect FLTK's color handling.

selection_color: Color

Widgets have a secondary color. This is usually used to color the widget when it is selected, although some widgets use this color for other purposes.

label: string

The label is printed somewhere on the widget or next to it. Its position depends on the align property; how it's drawn depends on the labeltype property..

labeltype: Labeltype

A labeltype identifies a routine that draws the label of the widget. This can be used for special effects such as emboss (Labeltype.embossed).

The value Labeltype.normal prints the label as text. See Labeltype for further documentation.

labelcolor: Color

The color used to draw the widget's label.

labelcolor is an index into an internal table of rgb colors. For most widgets this defaults to Color.black. See the documentation of Color for named colors and operations that affect FLTK's color handling.

labelfont: Font

The font used to draw the widget's label. Font is an index into an internal table of fonts. The default font is Font.helvetica; add Font.bold or Font.italic to add those styles: Font.helvetica+Font.bold. See Font for further documentation.

labelsize: integer

The point size of the font used to draw the widget's label. The FLTK default is 14.

callback: function

Most widgets are designed to respond to user interaction. Depending on the type of widget and the value of the when property, the function in the callback property will be called when the user takes action that directly affects this widget. For example, the callback runs when a Button is pushed, or when the user changes the value of an Input field.

argument: integer

Don't set this property; it's reserved for the use of the Lua FLTK runtime system.

when: When

The when property is a set of flags used by subclasses of Widget to decide when to deliver a callback. If the value is When.never then the callback is never done. Other values are described in the individual widgets and in the When documentation.

visible: readonly boolean

An invisible widget never gets redrawn and does not get events. The visible property is true if the widget is set to be visible. A widget is only visible if visible is true on it and all of its parents.

Changing it will send Event.show or Event.hide events to the widget. Do not change visible if the parent is not visible, as this will send false Event.show or Event.hide events to the widget. redraw() is called automatically, if necessary, on this widget or its parent.

visible_r(): boolean

visible_r() returns true if the widget and all of its parents are visible. A widget is only visible if visible is true on it and all of its parents.

active: readonly boolean

active returns whether the widget is active. An inactive widget does not get any events, but it does get redrawn. A widget is only active if active is true on it and all of its parents.

Changing this value will send Event.activate or Event.deactivate to the widget if active_r() is true.

Currently you cannot deactivate Window widgets.

active_r(): boolean

active_r() returns whether the widget and all of its parents are active. An inactive widget does not get any events, but it does get redrawn. A widget is only active if active is true on it and all of its parents.

activate(): void

Activates the widget. See the active property for more documentation.

deactivate(): void

Deactivates the widget. See the active property for more documentation.

output: readonly boolean

Widgets that the output property is true of are "output only"; they don't receive any events. This is similar to not active widgets, except output does not affect how the widget is drawn.

set_output(): void

Makes this widget output-only. See the output property for more documentation.

clear_output(): void

Resets this widget's output-only status. See the output property for more documentation.

takesevents: readonly boolean

This property is true if the widget is visible, active, and not output-only.

changed: readonly boolean

changed is a flag that is turned on when the user changes the value stored in the widget. This is only used by subclasses of Widget that store values, but is in the base class so it is easier to scan all the widgets in a panel and run the callback on the changed ones in response to an "OK" button.

Most widgets turn this flag off when they perform a callback, and when the program sets the stored value.

Tries to make this widget be the Fl.focus widget, by first sending it an Event.focus event, and if it returns non-zero, setting Fl.focus to this widget. You should use this method to assign the focus to an widget. Returns true if the widget accepted the focus.