[linrad] Linrad-02.08 and X11 peculiarities

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi All,

Linrad-02.08 is now uploaded. With this version I
hope the multi-threaded structure is stable.

The Microsoft Windows version is still incomplete,
it does not have any srive routines for hardware yet.

The X11 version should now have all the functions
that are available with svgalib. If you select a 
lower colour depth, down to 256 colours, faster
waterfalls can be selected.

*************************************************
There is one peculiarity with X11 that I would
like to know more about:

Linrad uses XPutImage(d,w,gc,x,0,line,0,line,screen_width,height);
to move a part of the screen image from memory to screen.
Moving the entire screen takes too much time. The problem is that
the sub-image from line to line+height has to be made 7 lines
larger than the desired area because copying is not actually
made from line to line+height, sometimes it is made from line+4
to line+height, other times it is from line to line+height-3.
It could even be worse than this, I have not investigated 
carefully.

The proble is that a fast waterfall writing say 300 lines per 
second will have to transfer 2400 lines per second. This increases 
the CPU load by about 15 % on top of the load caused by shifting 
the waterfall at about 20 Hz.

What worries me is that the number of required extra lines could be 
larger sometimes. Rather than adding four lines at the top and
three lines at the bottom I should use some data provided by the
X-server to compute what lines to send each time. Is there anyone
on this list who knows what to do?

73

Leif / SM5BSZ









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