Keyboard filtering

[whitebird001]

Hello,

In my MFC application I want a keyboard filter so that on some situations only expected keys are accepted.

Example:

An edit control accepting only binary digits (0 or 1), all other keys beeing rejected.

I think OnKeyDown has to be customized but I am not sure

Thank you in helping me.

Whitebird001

[Cpp_Noob]

have a look at this
Keyboard Hook

[unnamed]

Try subclassing the edit control and handle OnSysKeyDown().

Regards,
John
http://www.simpletools.co.in

[JohnCz]

Keyboard[/url]

Unnecessary, overkill.

Try subclassing the edit control

Subclassing is good.
Details:
Derive class using CEdit as a base class. Subclass control using Wizard. Add member variable using derived class for a variable type "control" (not a string). This will insert DDX calls necessary to subclass control.

handle OnSysKeyDown().

Insert handler for WM_CHAR message in CEdit derived class. In the handler, filter characters you need by returning from the handler without calling a base class. You can also consider beep to let user know that wrong character was entered.

[unnamed]

Insert handler for WM_CHAR message in CEdit derived class. In the handler, filter characters you need by returning from the handler without calling a base class. You can also consider beep to let user know that wrong character was entered.

Sorry, I had OnKeyDown in my mind.

[Igor Vartanov]

Example:

An edit control accepting only binary digits (0 or 1), all other keys beeing rejected.

I think OnKeyDown has to be customized but I am not sure

The task (as it exactly is) is solved by ES_NUMBER edit control style.

[VictorN]

The task (as it exactly is) is solved by ES_NUMBER edit control style.

How?
First it allows also digits from 2 to 9 to be entered.
Second (from this link):

ES_NUMBER
Allows only digits to be entered into the edit control. Note that, even with this set, it is still possible to paste non-digits into the edit control.
To change this style after the control has been created, use SetWindowLong.

[Igor Vartanov]

Sorry, you're right, I have missed the point of 0/1. But regarding possible paste, the requirement to filter edit box text changes is different from filtering key presses.

[VictorN]

... But regarding possible paste, the requirement to filter edit box text changes is different from filtering key presses.

Yes, of course!.
And I am sorry too, this part (about pasting problem) was not for you but for OP!