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# Wx::UpdateUIEvent

This class is used for pseudo-events which are called by Widgets
to give an application the chance to update various user interface elements.

## Derived from

CommandEvent

Event

Object

## Event table macros

To process an update event, use these event handler macros to direct input to member
functions that take a UpdateUIEvent argument.

evt_update_ui(id) { | event | … } | Process a EVT_UPDATE_UI event for the command with the given id.
EVT_UPDATE_UI_RANGE(id1, id2, func) | Process a EVT_UPDATE_UI event for any command with id included in the given range.

## Remarks

Without update UI events, an application has to work hard to check/uncheck, enable/disable,
show/hide, and set the text for elements such as menu items and toolbar buttons.
The code for doing this has to be mixed up with the code that is invoked when
an action is invoked for a menu item or button.

With update UI events, you define an event handler to look at the state of
the application and change UI elements accordingly. Widgets will call your
member functions in idle time, so you don’t have to worry where to call this code.
In addition to being a clearer and more declarative method, it also means you
don’t have to worry whether you’re updating a toolbar or menubar identifier.
The same handler can update a menu item and toolbar button, if the identifier is the same.

Instead of directly manipulating the menu or button, you call functions in the event
object, such as UpdateUIEvent#check. Widgets
will determine whether such a call has been made, and which UI element to update.

These events will work for popup menus as well as menubars. Just before a menu is popped
up, Menu#update_ui is called to process any UI events for
the window that owns the menu.

If you find that the overhead of UI update processing is affecting
your application, you can do one or both of the following:

1. Call UpdateUIEvent#set_mode with
   a value of UPDATE_UI_PROCESS_SPECIFIED, and set the extra style
   WS_EX_PROCESS_UPDATE_EVENTS for every window that should receive update events.
   No other windows will receive update events.
2. Call UpdateUIEvent#set_update_interval with
   a millisecond value to set the delay between updates. You may need
   to call Window#update_window_ui at critical
   points, for example when a dialog is about to be shown, in case the user
   sees a slight delay before windows are updated.

Note that although events are sent in idle time, defining a IdleEvent
handler for a window does not affect this because the events are sent from Window#on_internal_idle
which is always called in idle time.

Widgets tries to optimize update events on some platforms. On Windows
and GTK+, events for menubar items are only sent when the menu is about
to be shown, and not in idle time.

## See also

Event handling overview

## Methods

- UpdateUIEvent.new
- UpdateUIEvent#can_update
- UpdateUIEvent#check
- UpdateUIEvent#enable
- UpdateUIEvent#show
- UpdateUIEvent#get_checked
- UpdateUIEvent#get_enabled
- UpdateUIEvent#get_shown
- UpdateUIEvent#get_set_checked
- UpdateUIEvent#get_set_enabled
- UpdateUIEvent#get_set_shown
- UpdateUIEvent#get_set_text
- UpdateUIEvent#get_text
- UpdateUIEvent#get_mode
- UpdateUIEvent#get_update_interval
- UpdateUIEvent#reset_update_time
- UpdateUIEvent#set_mode
- UpdateUIEvent#set_text
- UpdateUIEvent#set_update_interval

### UpdateUIEvent.new

UpdateUIEvent.new(%(arg-type)Integer% commandId = 0)

Constructor.

### UpdateUIEvent#can_update

Boolean can_update(%(arg-type)Window% window)

Returns `true` if it is appropriate to update (send UI update events to)
this window.

This function looks at the mode used (see UpdateUIEvent#set_mode),
the WS_EX_PROCESS_UPDATE_EVENTS flag in window_,
the time update events were last sent in idle time, and
the update interval, to determine whether events should be sent to
this window now. By default this will always return `true` because
the update mode is initially UPDATE_UI_PROCESS ALL and
the interval is set to 0; so update events will be sent as
often as possible. You can reduce the frequency that events
are sent by changing the mode and/or setting an update interval.

#### See also

UpdateUIEvent#reset_update_time,
UpdateUIEvent#set_update_interval,
UpdateUIEvent#set_mode

### UpdateUIEvent#check

check(%(arg-type)Boolean% check)

Check or uncheck the UI element.

### UpdateUIEvent#enable

enable(%(arg-type)Boolean% enable)

Enable or disable the UI element.

### UpdateUIEvent#show

show(%(arg-type)Boolean% show)

Show or hide the UI element.

### UpdateUIEvent#get_checked

Boolean get_checked()

Returns true if the UI element should be checked.

### UpdateUIEvent#get_enabled

Boolean get_enabled()

Returns true if the UI element should be enabled.

### UpdateUIEvent#get_shown

Boolean get_shown()

Returns true if the UI element should be shown.

### UpdateUIEvent#get_set_checked

Boolean get_set_checked()

Returns true if the application has called UpdateUIEvent#check. For Widgets internal use only.

### UpdateUIEvent#get_set_enabled

Boolean get_set_enabled()

Returns true if the application has called UpdateUIEvent#enable. For Widgets internal use only.

### UpdateUIEvent#get_set_shown

Boolean get_set_shown()

Returns true if the application has called UpdateUIEvent#show. For Widgets internal use only.

### UpdateUIEvent#get_set_text

Boolean get_set_text()

Returns true if the application has called UpdateUIEvent#set_text. For Widgets internal use only.

### UpdateUIEvent#get_text

String get_text()

Returns the text that should be set for the UI element.

### UpdateUIEvent#get_mode

UpdateUIMode get_mode()

Static function returning a value specifying how Widgets
will send update events: to all windows, or only to those which specify that they
will process the events.

See UpdateUIEvent#set_mode.

### UpdateUIEvent#get_update_interval

Integer get_update_interval()

Returns the current interval between updates in milliseconds.
-1 disables updates, 0 updates as frequently as possible.

See UpdateUIEvent#set_update_interval.

### UpdateUIEvent#reset_update_time

reset_update_time()

Used internally to reset the last-updated time to the
current time. It is assumed that update events are
normally sent in idle time, so this is called at the end of
idle processing.

#### See also

UpdateUIEvent#can_update,
UpdateUIEvent#set_update_interval,
UpdateUIEvent#set_mode

### UpdateUIEvent#set_mode

set_mode(%(arg-type)UpdateUIMode% mode)

Specify how Widgets will send update events: to
all windows, or only to those which specify that they
will process the events.

mode may be one of the following values.
The default is UPDATE_UI_PROCESS_ALL.

enum UpdateUIMode { // Send UI update events to all windows UPDATE_UI_PROCESS_ALL, // Send UI update events to windows that have // the WS_EX_PROCESS_UI_UPDATES flag specified UPDATE_UI_PROCESS_SPECIFIED };

### UpdateUIEvent#set_text

set_text(%(arg-type)String% text)

Sets the text for this UI element.

### UpdateUIEvent#set_update_interval

set_update_interval(%(arg-type)Integer% updateInterval)

Sets the interval between updates in milliseconds.
Set to -1 to disable updates, or to 0 to update as frequently as possible.
The default is 0.

Use this to reduce the overhead of UI update events if your application
has a lot of windows. If you set the value to -1 or greater than 0,
you may also need to call Window#update_window_ui
at appropriate points in your application, such as when a dialog
is about to be shown.

[This page automatically generated from the Textile source at 2023-06-09 00:45:30 +0000]