OpenEuphoria

Re: Needing some Windows programming help

• Posted by Dan Moyer <danielmoyer at prodigy.net> Jun 11, 2007
• 582 views

DB James wrote:
> 
> CChris wrote:
> > 
> > DB James wrote:
> > > 
> 
> <SNIP>
> 
> > I'd take this problem the other way round:
> > 1/ draw your graph on a memory bitmap (Pixmap in win32lib)
> > 2/ handle the w32HPaint event fr your graph window and bitBlt() the relevant
> > section of the
> > graph.
> > 3/ To improve smoothness, your bitmap should be wider than the window
> > it will update, and, from time to time, just bitBlt() the "later" part onto
> > the "earlier" part.
> > 
> > This is scrolling on a double buffered window.
> > 
> > CChris
> 
> Hi CChris,
> 
> Thanks for the ideas on how to handle this.  You gave me a lot to think
> about.  I don't know yet how to "draw to a memory bitmap", but am not sure
> that is the best way to go.  If I could do that, I wonder if I couldn't go
> one better and write directly to the bitmap on the screen such that no
> flicker would occur and there would be the sort of automatic refreshing we
> expect in, for example, MS Paint.  There we could draw a square, fill it with
> color, and it would be refreshed no matter what obscuring happened to the
> window it was in.  (Being cautious, I just tried it and of course it worked.)
> 
> Unless someone else has a solution to suggest, I guess I'll read Petzold and
> poke around with Euphorians' contributions related to bitmaps/pixmaps...
> 
> --Quark

DB,

I think the idea behind CChris' suggestion is that any write from Euphoria 
directly to the screen will take a longer time to complete than the time
it takes to bitBlt() the (finished) pixmap to the screen; therefore, while
you're writing the data to the pixmap, although it takes some time, the
screen stays the same, ergo, no flicker.  When your program is finished
writing to the pixmap, then the subsequent bitBlt() happens sufficiently 
quickly that *that action* shows no flicker.

Of course, I could be wrong :)

Dan Moyer