Speeding up plotting widget

[John Tapsell]

Hi all,

  I'm trying to improve the plotting widget thing in the kde system
monitor (aka ksysguard).  Basically it draws white background,
horizontal/vertical lines, and then plots the cpu usage etc lines on
top.

  I am finding that this is taking around 30% of the CPU, which makes
it kinda useless for monitoring what the cpu usage is :-D

  The reason for it being slow is not obvious to me.

If I draw just a white background, it takes 1% CPU usage.
If I draw a white background + _dashed_ horizontal lines  (updating
twice a second), it takes up 10% CPU time  (on dual core.  so 20% of
one CPU).
If I draw a white background + _straight_ horizontal lines  (updating
twice a second), it takes up 1% CPU time



There seem to be other reasons as to why it's slow, but this seems to
be a good place to start.  Why would drawing dashed lines be so slow?
(It's about 10 horizontal lines, stretching across my screen (so about
1000 pixels long).

How can I try to speed this up?

Thanks!

John Tapsell