Re: Horiz motion: What is faster/better than redrawing pic moved 1 pixel to left 100x?

[John Cupitt ng-london org uk]

Chris Seberino wrote:

> Suppose I want to simulate a picture moving
> across a widget/pixmap.  I *could* erase it and
> redraw it moving it 1 pixel at a time.....
> 
> but...
> 
> is there a better/faster way to simulate movement
> regarding a picture???


Hi Chris, there are many, many techniques:

- use gtkcanvas

   high level OO canvas widget will do all the work
   for you ... it won't be the quickest thing ever
   though, since the compositing work is
   done on the application side (I think)

- double buffer

   make an offscreen pixmap inside the X server
   and do all your erase/redraw there ... when you
   want to update the screen, just copy the changed
   areas to the display

   pretty quick, and no flicker

- eor

   make an offscreen pixmap one pixel wider than your
   sprite, draw your sprite to that, then eor your
   sprite over itself, but offset by 1 pixel ... now
   draw your sprite to the display, then eor your
   offscreen pixmap over the top ... it moves!

   I'm not sure it's possible to go faster than
   this

John



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