Trap Special characters in a C++ keyboard hook.

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Hi ,

I have written a normal Low-level keyboard hook. I am able to trap correctly all alphanumeric keys in it. But am unable to trap special characters like @,#,$,? etc. All these keys require pressing of the Shift Key followed by an other key. Example for ? , we need to press Shift+ / keys and for say @ , we need to press Shift and 2 key.

Is there anyway to trap such special characters? Some sample code will be really helpful. Please note that I am using C++ .

Thanks for your help.

Posted 23-Feb-11 2:38am

Hellraiser123

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Chris Meech 23-Feb-11 12:19pm

How are checking for upper case or lower case? However you do that, the same applies for the 2 key being either a 2 character or an @ character.

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Emilio Garavaglia · Answer 1 · 2011-02-24T09:49:00

You are confusing different abstraction level.
What you call "special characters" are not special at all: they're just regular characters. They differ like an "a" differs form an "A".
But the problem is the level of "input" you are using.
A low level hook knows noting about "characters": it knows only about "keys" (the physical ones), and they are identified by their names (That - conventionally- are the same of the main letter printed on them - hence the confusion).

Characters are the result of a mapping between sequences of key pressures/releases and keyboard layout, that may be different from country to country (for example, on my keyboard, Shift+2 is '"' and and ? id shift+' and @is Ctrl+Alt+ò
The task to map keys (or keychord) to characters is a task of the keybord driver, that handles the low level event you hooked.

If you want to manage characters use "character oriented input functions" like _getch() or std::cin or other console oriented character functions (in case of console app) or handle WM_CHAR (but ensure your messageloop calls TranslateMessage before DispatchMessage) in case of Win32 App.

Rajesh Katalkar · Answer 2 · 2011-02-23T04:16:00

Solution 2

you might have to translate it using TranslateMessage api

Posted 23-Feb-11 4:16am

Rajesh Katalkar

CodyDaemon · Answer 3 · 2011-02-23T03:44:00

Solution 1

I believe the way that you have to do this, well the way I did it atleast, was to check for the status of the shift keys when you get the 'other' key message. i.e If you wanted to catch '?', then trap '/', and test for shift keys being pressed. If both are true then do your trap stuff.

if(key=='/' && bShiftPressed)
{
    doTrapStuff();
}

Posted 23-Feb-11 3:44am

CodyDaemon

Comments

Hellraiser123 23-Feb-11 10:55am

I can do that if there are just one or 2 such keys. But what If i want to trap any special key that the user may press on the Keyboard? Am a complete newbie to all this hooks and keyboard trapping. So please bear with me.

Sergey Alexandrovich Kryukov 23-Feb-11 22:42pm

At the level of hooks, there is not "special keys", forget it. Justin is right.
--SA

CodyDaemon 23-Feb-11 11:03am

What other special keys do you mean? Have you looked at:- http://msdn.microsoft.com/en-us/library/dd375731(v=vs.85).aspx <-- List of Virtual Key codes.

Hellraiser123 23-Feb-11 21:06pm

Yes. I dont want to do anything on press of say a special character like '@'. All I want to do is to store the special character like '@' in a buffer. So for that I need to trap the @ character. Thanks for replying.

CodyDaemon 24-Feb-11 6:27am

I am not sure what you are trying to do, but if you just want to log the special keys then you can just use your fav. string/list class and just append it to the string/list.

Sergey Alexandrovich Kryukov 23-Feb-11 22:43pm

Justin, you're right, my 5, but OP just cannot get it.
--SA

Espen Harlinn 25-Feb-11 8:00am

My 5 - good reply :)