Re: TTrackBar and Event

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#3656

From: Remy Lebeau (TeamB)
Date: Fri, 12 May 2006 08:12

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"Christophe MINETTI" <cminetti@ulb.ac.be> wrote in message
news:4464226B.8A469DBC@ulb.ac.be...

> I am using the function PeekMessage() to remove the huge amount
> of event sent by the OnChange event of a TrackBar component.

Why are you doing that?

> What kind of Window message is sent when one changes the trackbar position

As specified in the Win32 API documentation, a TrackBar control sends
WM_HSCROLL and WM_VSCROLL messages to its parent window.  Since the parent
window is a VCL window in this situation, the VCL repackages the messages as
CN_HSCROLL and CN_VSCROLL and sends them back to the TTrackBar for handling.
Using Spy++, I also see WM_MOUSEMOVE, WM_NCHITTEST, WM_USER, WM_PAINT,
WM_CAPTURECHANGED and WM_SETCURSOR messages being sent to the TTrackBar as
well while the thumb is being dragged by the user.


Gambit

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Subject: Re: TTrackBar and Event
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