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Date Posted: 07:28:19 01/30/01 Tue
Author: Michel
Subject: Re: Overlaid Cross
In reply to: Bob Villiers 's message, "Re: Overlaid Cross" on 16:10:49 01/29/01 Mon

Hi Bob,

The only hint I can think of is patience. This kind of programming requires trial and error, just getting a reference point and keeping track of the mouse coordinates. With the TRubberbandMouseHandler, there is the same kind of situation, where the image may be larger than the visible area, and the image may be scrolled. One suggestion may be to start from the TRubberbandMouseHandler, and replace the band by your cross.

Best regards,

>Reading back my message, I am not sure what I meant
>A few months ago i produced a demo which displayed a
>bitmap in a TPaintbox and marked a point on the bitmap
>with a cross.
>I am now working on the production version, the bitmap
>file has become a png file and the image now exceeds
>the width of the display area. ie. it needs to be
>I can display the png file in a TImageScrollbox and
>write the cross to an added canvas in a mouse handler.
>However, if the image (plus cross) is scrolled so that
>the marked area is off screen the cross is erased. I
>have a "Cross Visible" flag and know the cross co
>ordinates, but I do not see an event which tells me
>the image should now be visible and therefore re
>drawn. (I suppose it ammounts to an OnScroll event and
>writing this has given me a clue how to solve it. <g> )

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