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Is there a message when a control contents changes? [message #43844]

Tue, 04 November 2014 02:13

rxantos
Messages: 73
Registered: October 2011

Member

I want to enable/disable an Apply button inside a dialog if the contents of the controls inside it changes.

Assuming a dialog with many EditString controls. What would be the most efficient (if possible without polling) way to know if any of the controls inside the dialog changed?

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Re: Is there a message when a control contents changes? [message #43846 is a reply to message #43844]

Tue, 04 November 2014 19:53

Didier
Messages: 725
Registered: November 2008
Location: France

Contributor

Hello Rxantos,

basically all the GUI management is based on events, so if you wan't to do some action if a ctrl changes, use the callbacks of the controls for that (usually the names of the callback members are like : "when...." : WhenAction, WhenPush, ....
You will have to set the callback of all the ctrls you wan't to monitor inside you're dialog.

A nice feature about callbacks is that you can put several actions (callbacks) in one callback !!
You have to use the << operator for this like in this example :

(button.WhenAction << THISBACK(actionOne)) << THISBACK(actionTwo);

This allows you to monitor callbacks while still allowing normal use of the callbacks

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Re: Is there a message when a control contents changes? [message #43848 is a reply to message #43846]

Wed, 05 November 2014 08:17

jerson
Messages: 202
Registered: June 2010
Location: Bombay, India

Experienced Member

Hello Didier

That is a nice tip to remember.

Thank you
Jerson

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Re: Is there a message when a control contents changes? [message #43849 is a reply to message #43848]

Wed, 05 November 2014 14:09

mirek
Messages: 14255
Registered: November 2005

Ultimate Member

Important note:

WhenAction is triggered when USER changes the widget (I mean, if the change is a result of user-initiated input event). Changing value by client code does not trigger WhenAction.

(Of course, it also depends on how widget is actually implemented, but all widgets should follow this rule).

Mirek

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