[Xastir] CPU usage

[Curt Mills, WE7U]

On Wed, 13 Aug 2003, Dick C. Reichenbach wrote:

> On map redrawing?  Does the thread load the whole file first and then
> work with it out of memory, or do you process the points as it is loaded
> in?

It's processed a point at a time as we load.


> Also, another point, I noticed that when I change scale from close
> to far, If I have say, for example, Dayton.pdb, Columbus.pdb, and
> Ohio.pdb active, and I zoom out to include Indiana.pdb, Kentucky.pdb,
> and WestVirgina.pdb, it has to take the time to reload and reprocess,
> Dayton, Columbus and Ohio.  Why?  If the map points are already loaded
> in memory.

They're not already in memory.  They are processed, drawn, then
forgotten.  We don't cache anything in memory other than the image
we created while drawing.

What we have is:

    pixmap              maps
    pixmap_alerts       maps + alerts
    pixmap_final        maps + alerts + symbols/tracks
    da (drawing area)   same as last

We draw maps into pixmap.  We then copy that data to pixmap_alerts
and draw the weather alerts on top of it.  We then copy that data to
pixmap_final and draw symbols/tracks.  We then copy that to "da"
and it's then displayed on the screen.

The reason for these multiple layers:   If no zooming/panning is
going on, we can quickly draw starting at the alerts.  If no alerts
are changing, we start at the symbol/tracks.  This speeds things up
overall.

Once you starting zooming/panning, you have to start from scratch.

-- 
Curt Mills, WE7U                    hacker_NO_SPAM_ at tc.fluke.com
Senior Methods Engineer/SysAdmin
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