[Lazarus] Smooth scrolling label (marquee)
mschnell at lumino.de
Tue Nov 10 12:51:28 CET 2015
On 11/10/2015 12:30 PM, Luca Olivetti wrote:
> - it is very cpu intensive (I have to put it over a picture, so the
> invalidate will also force the repainting of the bitmap I guess)
The only cure for this is using the graphic processor: only once create
a wide pixel array from the text and then use Direct X (Open GL or
similar API) to display part of the text "behind" in a rectangle.
> - the minimum timer interval is 10ms, and even that it's not
> guaranteed (the resolution on windows is around 15ms and I got a very
> different speed of the label using 10ms under virtualized windows xp
> and a real windows 7 machine)
> - with such a low value (10ms) sometimes the application gets bogged
> down, specifically it cannot process the modal dialog I use to shut
> down the application.
What you are trying to do is a multimedia application and hence "soft
realtime". This can't decently be done with "normal" desktop-Type
> - I solved the flickering by setting DoubleBuffered to the containing
> widget (a TPageControl), but, again, I think that takes its toll on
> cpu usage.
> I tried to use a thread (with synchronize) instead of a ttimer to
> obtain a lower interval, but that only compounds the problems.
> Any suggestion
A thing that we (company) do for a similar application (moving text
"behind" a rectangle) is programming the "movie" in Adobe Flash and have
the flash player show it on the screen (multiple instances). Works great !
A new development supposedly should avoid Flash (as support for same is
dying out) and use HTML4 instead.
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