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Degging Windows Programs

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  • Chris Boss

    >Then in the "main loop" for my dialog (just after the
    >FUNCTION=action statement), I put the statements
    >IF alertvalue>"" THEN MSGBOX alertvalue:alertvalue=""

    The first NO, NO is "Never" try to display a messagebox from within a DialogBox (or window Proc) Procedure unless it is done when a specific message is processed (like WM_COMMAND).

    By putting the messagebox command in a place where it can be executed by any Dialog Message (ie, where you put it), you may be trying to display a messagebox during a particular message that Windows finds offensive.

    Do NOT assume that a Dialog Procedure is dormant. There are a bunch of messages that are processed before a Window (Dialog) is even displayed, ie. WM_NCCREATE, WM_INITDIALOG and possibly others.

    By putting the messagebox command in a place that where it may execute during a windows message that does not like it, you can cause problems, even GPFs.

    If you move your messagebox command to the WM_COMMAND message and test for say a Button press and then execute it, it should work fine.

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  • Joe Speroni
    I appreciate your taking the time to answer, but all strings are greater
    than the null string. That's not it, but I did change the code anyway.
    (just in case). No my problem has some other origin.

    Leave a comment:

  • Matthew Berg
    If you are testing alertvalue to see if it has a value, why do you use the comparison operator ">"? Should that not be IF alertvalue <> "" THEN ...

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  • Joe Speroni
    started a topic Degging Windows Programs

    Degging Windows Programs

    I declared a GLOBAL value for debbuging in my windows

    GLOBAL alertvalue AS STRING

    then defined a Callback function


    and called the function from dialog button CALL.

    Then in the "main loop" for my dialog (just after the
    FUNCTION=action statement), I put the statements

    IF alertvalue>"" THEN MSGBOX alertvalue:alertvalue=""

    I never get a MSGBOX. Why isn't alertvalue being
    set, and the MSGBOX showing its value?

    Is there another smarter way to display values seen
    inside CALLBACK functions?