Slow text rendering in KDE.

petelewis · 2009-04-09 11:58:02

Hi there,

I recently starting getting quite fed up with how I felt that writing stuff in kate (or kile, or kdevelop etc) was very slow and unresponsive. The effect I was getting is that there was a big delay (of up to a second or two sometimes) between hitting the key and the character appearing on the screen. It's especially noticeable if you type a whole bunch of stuff very quickly - wait for the screen to catch up!

I did a few experiments, and managed to rule out any kate plugins etc, though I wasn't experiencing the same thing in konsole / yakuake. Also, I noticed that if I made the kate window smaller, so not so much of the text I was editing was visible, it would speed up. In fact, the size of the lag seems proportional to the amount of text visible and being rendered while typing (even if that text is not being changed).

I fiddled with a few settings and noticed that I could fix the lag (i.e. completely get rid of it) by disabling "sub-pixel rendering" in KDE's font settings (and restarting the relevant program). Incidentally, it's not enough to have the the "sub-pixel rendering" box enabled and select "none" - that still creates the lag.

Therefore, I can work around this for now by unchecking the box, but it got me interested in this. I'm thinking that it's something to do with the way Qt is rendering the fonts, possibly to do with my intel graphics driver, but possibly not.

So this post is twofold really; firstly to let others know of the workaround in case they're also experiencing this, but also to ask around to see if other people are noticing this, with a view to filing a bug / feeding back to developers / deciding that I need newer hardware.

My specs:
- KDE from kdemod 4.2.2
- intel 945GM graphics card onboard
- xorg intel driver (currently version 2.3.2, but I've experienced the same with earlier and later versions, up to the current git version)
- XServer 1.6, though again, I've experienced this with 1.5 too.
- Using EXA for rendering, though again I've had the same experience with XAA. Haven't tried UXA yet.

So... anyone any contribution?

Cheers,

Pete.

onguarde · 2009-04-15 09:28:06

If the problem is kde specific, u might wanna try moving .kde4 settings folder and restarting?

Also, try removing custom plasmoids from aur if you have any.

Not too sure if its a graphics issue.

petelewis · 2009-04-29 13:45:37

It seems this is to do with Qt, and it's been fixed in Qt 4.5.1. It's in their changelog:

http://www.qtsoftware.com/developer/cha … nges-4.5.1

Pete.

jwcxz · 2009-04-29 13:59:24

I experience sever slowdown in scrolling in Kate with my Intel 965. However, I do not experience any problems in other applications (Kontact, Konsole, etc.). I did not experience the problem (at least noticably) when I was using Xorg 1.4 and XAA. Hopefully, 4.5.1 resolves this issue for me as well... It's harder to deal with large code files now.

Arch Linux

#1 2009-04-09 11:58:02

Slow text rendering in KDE.

#2 2009-04-15 09:28:06

Re: Slow text rendering in KDE.

#3 2009-04-29 13:45:37

Re: Slow text rendering in KDE.

#4 2009-04-29 13:59:24

Re: Slow text rendering in KDE.

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