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Old 09-16-04, 01:43 PM   #1
pdcruze
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Default RenderAccel and antialiased fonts

I've recently had the courage to enable RenderAccel in my XF86Config-4 config file and must say that the speed improvements under KDE 3.2.3 are impressive. The speed under konsole is terrific. Now its rare for XFree86 to be consuming lots of cpu cycles.

However, I have noticed that font rendering is slightly worse when RenderAccel is enabled. I have a LCD monitor and in the KDE control settings, I've enabled antialiasing and sub-pixel hinting. When RenderAccel is disabled, fonts are rendered beautifully. They're really nice - much better than under Windows. But when RenderAccel is enabled, the fonts are still antialised but they're more jagged than before. It's as if the sub-pixel hinting is not working (my theory).

Has anyone else noticed? Any suggestions or work-arounds?

FYI: I'm using the 6111 driver. I have a Geforce 5200, kernel 2.4.27, XFree86 4.3, KDE 3.2.3. Using Debian testing. I have both an LCD and CRT monitor connected and am using TwinHead settings.

Cheers,
Patrick
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Old 09-16-04, 02:08 PM   #2
PrakashP
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Default Re: RenderAccel and antialiased fonts

I haven't noticed any difference. In my case (also using an LCD) fonts are using sub-pixel hinting and they look nice. But in fact most of the time I used acceleration, so I don't really know whether the look better wthout. but it can't be much, if it is they case, otherwise I would have noticed the few times I deactivated accel.
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Old 09-16-04, 02:34 PM   #3
pdcruze
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Default Re: RenderAccel and antialiased fonts

Maybe you should try it again with and without RenderAccel. There's definitely a difference. It's not a huge one but it is there nonetheless - well, at least on my system.

I've attached two small screenshots to demonstrate. They're taken from the frontpage of Slashdot using Konqueror. The first is without RenderAccel enabled and the second has it enabled.


Cheers,
Patrick
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Old 09-16-04, 06:37 PM   #4
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Default Re: RenderAccel and antialiased fonts

renderaccel has several known bugs that should be resolved in the next nvidia linux driver release so the best bet is just to wait for a new driver.
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Old 09-17-04, 02:05 AM   #5
PrakashP
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Default Re: RenderAccel and antialiased fonts

Looking at your screenshot I indeed would say that the second one doesn't use subpixel hinting. I use Firefox and it clearly uses subpixel hinting even with render accel.

Opening Konq it also seems it does not use subpixel hinting with render accel, so is it a prohlem with konq?
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Old 09-17-04, 03:05 AM   #6
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Default Re: RenderAccel and antialiased fonts

Quote:
Originally Posted by PrakashKC
Looking at your screenshot I indeed would say that the second one doesn't use subpixel hinting. I use Firefox and it clearly uses subpixel hinting even with render accel.

Opening Konq it also seems it does not use subpixel hinting with render accel, so is it a prohlem with konq?
You explicitly enable Subpixel hinting in Control Center->Appearance->Fonts for kde.
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Old 09-17-04, 03:37 AM   #7
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Default Re: RenderAccel and antialiased fonts

Yes I know and I did that.

Hmm, it really seems some kde issue with render accel. Kwrite doesn't use subpixel hinting, as well.

Yup, Gnome is not affected. Just opened gedit and it does subpixel-hinting.

I use kde3.3, xorg-x11-6.8.
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Old 09-17-04, 04:03 AM   #8
PrakashP
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Default Re: RenderAccel and antialiased fonts

This starts getting stupid: After several times switching hinting on and off, kwrite and kedit finally use subpixel hinting, but kate and konq *don't*. What is this?
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Old 09-17-04, 04:07 AM   #9
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Default Re: RenderAccel and antialiased fonts

Ok, this really seems to be a driver issue:

Opening with kwrite I get subpixel hinint (most of the time). I move a window over it and away, no more hinting, just normal aa.

Strange enough using gedit, subpixel hinting stays.

Hello Nvidia?
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Old 09-17-04, 04:11 AM   #10
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Default Re: RenderAccel and antialiased fonts

So, here is an example of it.

Look at the W of SOFTWARE. Left without hinting, right with. (parts of the right windows are redrwan, so no more hinting...)

Moving a kde windo is OK, hinting stays, just on redraw hinting goes away.
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Old 09-17-04, 04:22 AM   #11
pdcruze
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Default Re: RenderAccel and antialiased fonts

I've just tried using Firefox and with RenderAccel enabled, I get no sub-pixel hinting. :-(

Ditto any other KDE apps. Ditto OpenOffice.org.

I think the way you can tell if its working is to take a screen snapshot and magnify it by, say, 400%. If the snapshot uses colours to antialias the font then its using sub-pixel hinting. If its only using greyscale to antialias then there's no sub-pixel hinting. Take a snapshot of text using an italic font is easiest because almost all of the text will need antialiasing.

I wonder if it is a dual-head problem? Or maybe it simply is a nvidia driver bug.
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Old 09-17-04, 05:19 AM   #12
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Default Re: RenderAccel and antialiased fonts

Do you have gnome installed? It has a utility itself to enable and disable aa hinting.

OpenOffice never gave me subpixel hinting, like all pdf and ps viewer I tried.
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