Re: Flicker free scrolling

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Sergey Tkachenko

Posted: 02/17/2002 23:56:51

I still cannot notice any flicker.

Please note: two different techniques are used for scrolling.

1) If background style = bsNoBitmap or bsTiledAndScrolled. RichView uses

ScrollWindowEx to scroll existing contents, and redraws only newly appeared

area.

What's why animation of image and text color does not work in this case.

2) In other cases, RichView completely redraws its window on scrolling.

If you set rv.FullRedraw = True, it will always redraw its window

completely.

I do not see flicker in either mode. Moreother, I think that flicker is

impossible even theoretically, because background is not cleared, and new

image is drawn directly to the screen as bitmap.

May be this is a LCD monitor quirk?

> Actually you can see this yourself by doing the following to your

> "Multi-Demo". Go to the Demo6Frm.pas portion and set the following

property

> of the TRichView component (ie; rv) as follows:

>

> rv.backgroundstyle := NoBitMap;

>

> Now run and choose the credits portion of the demo.

>

> Did some research on this and can see why you might not have spotted it. A

> red or darker color background or bitmap, such as the one you are using in

> the demo, tends to mask the problem. It is much more apparent on a white

> background though or lighter color bitmap. My experiments using a large

> number of backgrounds colors and bitmaps and combinations tends to support

> what I found out.

>

> Another thought is that use of the TTimer component may introduce enough

of

> a delay to make flicker perceiveable against light colors and/or bitmaps.

>

> BTW I am running then demo on a brand new 1.2 Ghz WindowsXP Pro machine

> using a flat screen monitor.

>

> Regards;

>

> Bob Dalton

>

>