LB Booster: trapclose error

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General >> Suggestion Box >> trapclose error
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trapclose error
Post by Alincon on Aug 22^nd, 2016, 3:58pm

If the destination label in a trapclose statement does not exist - perhaps a spelling error - I don't see any error message. It looks like the program is hung up, and the window will not close.

I would like to see some kind of error message, perhaps at the bottom of the screen.

r.m.

Re: trapclose error
Post by Richard Russell on Aug 22^nd, 2016, 5:56pm

on Aug 22^nd, 2016, 3:58pm, Alincon wrote:

I would like to see some kind of error message, perhaps at the bottom of the screen.

I don't think there's any practical (and safe) way that can be achieved, sorry. Hopefully testing would quickly lead to a realisation that the trapclose isn't working.

For your interest, the difficulty arises from the fact that an event handler can be specified in so many different ways:

A 'do nothing' event: []
A branch label: [handler]
A subroutine name: handler
A word returned by INPUT: HelloWorld

I wonder how many people remember (or ever knew) that the fourth option exists:

Code:

    button #w, "Click Me", ButtonClicked, UL, 50, 50
    open "Test" for dialog as #w
    #w "trapclose QuitNow"
    do    
      input r$
      print r$
    loop until r$ = "QuitNow"
    close #w
    end

LB 4 doesn't allow the fourth kind of event handler (a word returned by INPUT) with trapclose, but LBB treats all events alike so it does.

Richard.