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Programming >> Liberty BASIC language >> Control keys capture (i.e. F1 for help)
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Control keys capture (i.e. F1 for help)
Post by flotulopex on Mar 24th, 2014, 1:27pm

Hi there,

I was wondering if some more keys than the usual "Ctrl", "Alt", "Esc" etc such as the standard F1 (for "help") could be captured (scanned) within an LBB compiled program?

IMHO, it is a very restrictive usage to enable this ability only in graphic windows or am I wrong?
Re: Control keys capture (i.e. F1 for help)
Post by Richard Russell on Mar 24th, 2014, 2:45pm

on Mar 24th, 2014, 1:27pm, flotulopex wrote:
I was wondering if some more keys than the usual "Ctrl", "Alt", "Esc" etc such as the standard F1 (for "help") could be captured (scanned) within an LBB compiled program?

The same question (or something very like it) was asked recently over at the LBB Yahoo group:

https://groups.yahoo.com/neo/groups/lbb/conversations/messages/1093

My suggestion was either to test the key asynchronously (the example program keypress.bas is supplied with LB 4.04), when that is acceptable, or if you must see the keypress 'event' to use a Windows hook.

This program illustrates how you can use a WH_KEYBOARD_LL hook to monitor keypress events. It works with function keys just as well as regular keys:

Code:
    open "Hook test" for text as #w

    struct kbhs, vkCode as ulong, scanCode as ulong, _
                 flags as ulong, time as ulong
    callback lpfnHook, KeyboardLLHook(long, ulong, ulong), long

    calldll #user32, "SetWindowsHookExA", _
         _WH_KEYBOARD_LL as long, _
         lpfnHook as ulong, _
         0 as long, _
         0 as long, _
         hHook as ulong

    wait

function KeyboardLLHook(lMsg, wParam, lParam)
    kbhs.struct = lParam
    if wParam=256 print chr$(kbhs.vkCode.struct);
end function

It doesn't directly address your question but in LBB you can 'program' a function key to return any string you like in the INPUT statement, by incorporating a little bit of BBC BASIC code (here the |M signifies CR):

Code:
    !*key 1 "Hello world!|M"
    do
      input r$
    loop until 0

Richard.