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FreezingFire · **Admin Team** Joined: 23 Jun 2002 Posts: 3508

Hi... I'm facing a problem about flicker when updating a TEXT element.
Try this script to see what I'm talking about. The flicker can be somewhat
corrected by splitting the clock display up into separate texts and just
updating those separately. But I want to add in an option for custom font
and since fonts are different sizes/widths, breaking the text up into parts
will not work always.

Does anyone know of any solutions that will get rid of this flicker?

Thanks in advance! Very Happy

jules · Posted: Sat Nov 06, 2004 10:23 am Post subject:

You must have a slower computer than me because if you hadn't mentioned it, I wouldn't have noticed it. I think it's just the usual Windows screen redraw. It takes a noticeable time to redraw something that big. I don't think there is anything you can do about it.

With bitmaps, in a lower level language, you can reduce flicker by double buffering. You keep two copies of the bitmap and switch from one to the other instead of redrawing the existing one. But you can't do that in VDS, and you can't do it at all with text elements.

Skit3000 · Posted: Sat Nov 06, 2004 12:14 pm Post subject:

Hi FreezingFire,

Over here it was also flickering. The following code reduced it a lot, but it still seems that it doesn't work 100% good... Rolling Eyes

Serge · Posted: Sat Nov 06, 2004 1:04 pm Post subject:

hi ff,

i haven't tried this but i reckon that if you just change each digit when needed, that would reduce the flicker on the items that don't change

this means having to separate each digit in your time HH:NN:SS and dealing with each one individually and separately

your routine would require that you do not redraw an item unless it needs to be changed

serge

FreezingFire · **Admin Team** Joined: 23 Jun 2002 Posts: 3508

Thanks guys for the help Smile

I think I'm going to have to just do separate
digits.

PGWARE · **Web Host** Joined: 29 Dec 2001 Posts: 1565

Hey Julian,

In delphi there is a property DOUBLEBUFFERED for Tform which you can set to the Form to TRUE. That will cause everything to become doublebuffered.

I'm not sure if it's available in the version of delphi you guys are using when developing vds though. That could be a optional style added to the form?

Garrett · Posted: Sat Nov 06, 2004 6:25 pm Post subject: Re: Flicker

Skit3000 · Posted: Sat Nov 06, 2004 6:41 pm Post subject:

PGWARE · **Web Host** Joined: 29 Dec 2001 Posts: 1565

Any image and all drawing operations on the form would have to be double buffered as well, which means double the memory consumption. Slower I don't think; unless the app is on a slow computer to begin with - then again any animations or images probably look pretty bad on that computer; so the user isn't expecting much.

It's why a DOUBLEBUFFER style would be nice so it can be turned on or off depending on if it is really needed.

jules · Posted: Sun Nov 07, 2004 11:37 am Post subject:

I think Skit's method would work if TEXT elements weren't transparent. There would be no need to hide and show the first (lower) of the two elements. Try it in VDS 4. VDS 5 TEXT elements are transparent in order that they show the Windows XP theme background, so you can see the lower element through the upper one, and I think that this causes a redraw that results in the flicker.

I wasn't aware that Delphi supported double buffering. It doesn't seem to appear as a property in the object inspector anywhere. If it's available in the version of Delphi that is used to develop VDS 6 then I dare say that it could be made an option.