Keyboards


A. Using the Keyboard - Keyboard Handlers
If you want to use other keys on the keyboard or allow commands in your game , you would use a keyboard handler. Do a "Dictionary" search on "key" and you will see many useful keyboard handlers to detect almost any key or combination of keys from the keyboard.

We will look at the most commonly used ones:

1. keyDown message handler

    Handles most of the letter keys on the keyboard. (It does not give the arrowkeys)
        on keyDown x
            // x contains the key e.g. "n" if you pressed the n, "d" if you pressed the d, etc
        end keyDown

    example
            on keyDown x
                if x is not a number then
                    answer "numbers only please"
                end if
            end keyDown

2. keysDown() message function

    Handles a number of keys pressed (and cases when the user holds the key down too long). Since this is a function and not a message, it can be used inside another message handler.

     example

           on movePlayers
                if keysdown() contains 119 then
                 ....
                end if
           end movePlayers

    A good example would be using the keysdown() function to determine which key was pressed for a 2-player game. All the keys have numbers and every key on the keyboard can be identified.

            Player 1 will use the arrow keys which have the following number codes:
                left   =    65361
                up    =    65362
                right  =   65363
                down =   65364

            Player 2 will use the keys: ASD and W which are on the left side of a keyboard:
                left (A)   =    97
                up (W)   =  119
                right (D)  = 100
                down (S) = 115 

3. rawKeyDown message handler

    Handles more keys but gives the ASCII value instead of the face value

        on rawKeyDown x
               // x contains the key e.g. "110" if you pressed the n, "100" if you pressed the d, '65361' for the left arrow key, etc 
       end rawKeyDown

B. Seeing what the handlers return for each key on the keyboard

        To see the number for a key, add this code to the card script:

on updateScreen
   put keysdown( ) into msg
   send updateScreen to me in 20 millisec
end updateScreen    

            then add a button on the card:

on mouseUp
   updateScreen
end mouseUp

As you press every key on the keyboard, this will show the return value of each key as you press it, in the msgbox (This is one of the icons on the Edit Bar of LiveCode).

Take out that line of code when you have noted the numbers of all the keys that you need to handle.


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