Re: Program lockup waiting for messages

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#8197

From: Dennis Jones
Date: Mon, 15 Nov 2004 17:23

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"Jeff" <Jeff@nospam.com> wrote in message
news:4198d752$1@newsgroups.borland.com...
> Sure, here is one message being sent:
> void __fastcall TfrmMain::btnStartClick(TObject *Sender)
> {
>     SendMessage(WinHandle, WM_STARTSCRIPT, 0, 0);
> }

There's your problem(s).

1. SendMessage() doesn't return until the message has been handled.
2. VCL event handlers (like your button click handler) are handled in the
main VCL thread, and if an event handler blocks, everything grinds to a
halt.

You will probably want to create a separate thread that sends the message
and waits for the reply.  Or, alternatively, if your app does not have to
wait until the caller is done before continuing, use PostMessage instead.

- Dennis

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From: "Dennis Jones" <nospam@bogus.com>
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Subject: Re: Program lockup waiting for messages
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