Re: GnomeCanvas vs. gtk-drawing-area (fwd)


GnomeCanvas uses splitted updating model, i.e.

- update method, which recomputes GnomeCanvasItem internal state, if
something is changed in item parameters. During update items request
redrawing affected portion of screen.
- render method, which draws actually changed area to screen.

During animation, you probably will request updating the actual animation
item, which itself request redrawing affected screen area. If program does
not touch (request updating) background, it will not be updated, nor
request it any redrawing itself.
You can even request redrawing much more fine-grained area (microtile
array), so for example, if you request update of hollow rectangle, only
(approximate) area of its outline will be redrawn, not its inner area.

Lauris Kaplinski

On Sun, 23 Jan 2000, Jacques Fortier wrote:

> Hi,
> 	I'm working on a program that currently uses a GtkDrawingArea to
> render artwork, and I'm considering switching to GnomeCanvas.  However, I
> want to make sure that the canvas is fast enough for my needs.  I'm doing
> animation, and updating 40 times per second, so I use a dirty rectangle to
> minimize the rendering to the screen as much as possible.  Since I have a
> large background image that will cover the entire canvas, I'm worried that
> the canvas might try to update the whole thing every time, which would be
> a real drag.  Is this the case, or is the canvas smarter than this?  Is
> the canvas what I want to use here, or is there something better?
> Thanks,
> 	Jacques Fortier
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