Re: performance of goocanvas

[Damon Chaplin <damonachaplin gmail com>]

On Wed, 2013-11-20 at 09:52 +0900, D M German wrote:

> To be honest, I am not sure. I have created a good test case.
>
>
>
> http://turingmachine.org/~dmg/temp/test.xoj
>
> It is a gzip XML file. You can inspect it with gunzip -c <file> 
>
> Each stroke is a polygon. Most letters will be around dozens of strokes.
>
> Open the file and make sure that you have xournal in continuous mode
> (Menu: View/Continuous).
>
> I suspect you can get xournal installed from your Linux
> distribution. Try opening the file. it will be slow, but once open, the
> scrolling is smooth. 
>
> If I try to open it with the version that has gtk3 (it is also slow to
> load, so be patient :) but then it is very slow to scroll. It slows when
> it has to display a new page.
>
> I am not saying it is not a bug in my code :) that I might have
> introduced during porting, so I will also inspect the scroll event to
> make sure that I am not doing anything to slow it down.

I don't think the problem is drawing. I put a "return;" statement at the
top of the GooCanvasPolyline's draw function so it didn't draw anything,
but it was just as slow!

I think the problem may be that you are sometimes changing items when
the canvas is scrolled, and this causes the canvas to have to
recalculate the bounds of lots of items, which is slow.

What changes are you making when the canvas is scrolled? Is there a way
to avoid them?

Damon