[Kde-accessibility] [PATCH] Fix for Kmag redraw problems

[Olaf Jan Schmidt]

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[Sarang Lakare]
> The patch does what it is supposed to, but the CPU usage increases
> after applying this patch.

I cannot reproduce this. In all my tests, the CPU usage is more or less 
identical with or without the patch.

> I tried to find the reason, but it is not very obvious. This was my test
> case: Zoom level 8, kmag window pretty large, refresh set to very low.
> Run kmag with and w/o the patch. w/o the patch, on my machine, the CPU
> usage is a constant 75%, while with the patch, the CPU usage is 100%.

On my computer, there is a strange jump from 5% CPU usage to 100% when the 
size of the window exceeds a certain size. There is a sharp "border" 
between the two states - the CPU usage is 5% up to a certain limit, and 
if you increase the window size one pixel further, it suddenly jumps to 
100%. This does not depend on the patch, so I believe it is rather a 
problem in already existing code.

> This happens even when the selection window is not shown.

I have checked several times that the new code behaves identical to the 
old one if the selection widnow is not shown.

> My guess is that KMagSelWin is getting a refresh call when it
> shouldn't.. other than that I see no reason for the jump in CPU usage.

The KMagSelWin is hidden when it isn't shown - so it cannot get a refresh 
call. If there really was an increase in CPU usage when the window is not 
shown, then there would be a grave bug in KWin and Qt, which couldn't be 
fixed inside of KMag. But as I said, I cannot reproduce this increase in 
CPU usage.

> I think this should be fixed before applying the patch.

While showing the selection window, there must indeed be a small increase 
in CPU usage, as the redraw problems can only be fixed by making sure 
that proper redraw events are sent. This small CPU increase cannot be 
avoided unless we take the opinion that redraw bugs are OK.

In the long term, I am thinking about adding an option to KMag that allows 
to move and resize the KMagSelWin by grapping the border - we could 
implement (optional) resize and move handlers for the window, or just 
allow to set the border size a bit bigger for easier grapping.

Olaf.

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