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Old 12-07-05, 04:45 PM   #13
pete4nv
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Default Re: 1.0.8174 DPI computation incorrect

good. 75DPI is the fallback and not that high a resolution. When fonts "look like crap" it's a sign of improper DPI for one thing. Check your monitor specs and see how much more you can tweak. The lower your window size, the lower your dpi. Roughly speaking:

16000x1200 = 112x112 (my case)
1280x1024 = 90x96
1024x768 = 80-90, 80-90

Really, the key will be setting everything up properly, i.e. scan frequesncies, display dimensions, and depth. It's a lot of work, but once set up, it's great! Good luck
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Old 12-07-05, 05:03 PM   #14
Lethe
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Default Re: 1.0.8174 DPI computation incorrect

OK, explain how I get monitor DPI size - what do you mean by maximum?

I have a Flatron 795FT plus... I cannot find the DPI info anywhere?

But it is getting better...

Nick

EDIT! OK, I got it. You meant the 'real display' size. Well, I added that, and all fixed!!!!

dimensions: 1024x768 pixels (325x247 millimeters)
resolution: 80x79 dots per inch
depths (7): 24, 1, 4, 8, 15, 16, 32

I think perhaps that needs a little tweak, but I am there. Thanks for help again.
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Old 12-07-05, 05:51 PM   #15
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Default Re: 1.0.8174 DPI computation incorrect

I got this perfect now.

It needs to be explained in easy terms... I am a hardened Linux user of 6 years, and I didn't know this.

So, here is basically what happens in real layman terms.

All fonts are 'rendered' to the display - they have to be rendered on the fly to get the different sizes (re HTML <font> tags), else you would have a font directory many GB in size to hold all the fonts bitmaps. The rendering depends on REAL SCREEN size you see.

An image is delivered as 'is' - an image has an explicit size, and therefore is delivered 'as is', so this is why only fonts are effected.

OK, that bit out the way.

Now imagine you have a bit of rubber, and drew a large 'A' on it. If you stretch the rubber sideways, the 'A' would look all out of shape - too wide and fat. Same if you stretched it longways - it would be skinny and tall.

So, if your REAL display size is incorrect the X server uses this, all the fonts will 'slightly' stretched one way or another. The only way to get fonts delivered (rendered) correctly is to make sure they are draw on the display size you SEE (not on the rubber, as if display size is incorrect, the rubber gets 'stretched' to fit your monitor screen) - that means get the display size correct.

A big thanks to Pete4nv for his help here. I learnt a lot.

Nick
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Old 12-07-05, 07:36 PM   #16
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Default Re: 1.0.8174 DPI computation incorrect

Quote:
Originally Posted by Lethe
I got this perfect now.

It needs to be explained in easy terms... I am a hardened Linux user of 6 years, and I didn't know this.

So, here is basically what happens in real layman terms.
Thanks for the ´word-image´. Rubber band is a good analogy. When I bought this notebook I used a ruler and info from the web to tweak the 15.4" widescreen. I'll add the rubber picture to what I already have in xorg.conf:

Section "Monitor"
[...]
# Size gotten from http://www.prismo.ch/comparisons/notebook.php
# Size Diagonal Width Height Ratio Area Density at 1280x800
# 15.4" 39.12cm 33.17 20.73 8:5 688 cm2 98 pixels per inch
# I've set the width to 331 instead of 332 to get a uniform
# "DPI set to (98, 98)". Otherwise it would be (97, 98).

DisplaySize 331 207 # Aspect ratio 1.6:1 (8:5)

Mvh
Mats Johannesson

PS: That site also has a link to desktop flat panels. All these numbers are generally applicable if you lack screen documentation: http://www.prismo.ch/comparisons/desktop.php

Last edited by Voluspa; 12-07-05 at 07:55 PM. Reason: Add PS
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Old 12-07-05, 08:31 PM   #17
aritger
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Default Re: 1.0.8174 DPI computation incorrect

I apologize for the DPI confusion introduced in 8174.

For reference, information about how the NVIDIA X driver computes DPI is available in Appendix Y of the README:

http://download.nvidia.com/XFree86/L...ppendix-y.html

I think the behavioral problem with 8174 with UseEdidDpi is that the driver computes DPI using the "optimal" resolution of the display device (this is normally what is reported as the Detailed Timing in the display device's EDID), rather than what modetimings are set on the display device.

DPI cannot easily change once X is up and running (though it would really make sense for the DPI to change when you change resolution), which is one reason we opted to go with the "optimal" resolution, as inferred from the EDID. We also chose not to use the virtual size of the X screen, since that may be much larger (for example, if you are in TwinView). Perhaps the right compromise is for UseEdidDpi to compute the DPI based on the resolution of the first mode requested in the X configuration file. We'll investigate doing something like that in a future release.

The Xorg group has recently done some work to allow for more dynamic setting of DPI (when your mode changes); we will also try to utilize that in the future.

If the UseEdidDpi behavior gives you problems with 8174, you can use the "DPI" option to override; for example:

Option "DPI" "112x112"

Sorry again for any confusion.
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Old 12-08-05, 12:38 AM   #18
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Default Re: 1.0.8174 DPI computation incorrect

My X logfiles for the case where DPI is not calculated at all because the size is missing in EDID information (although it's obviously not).
I worked around the problem by specifying the size in xorg.conf.
Attached Files
File Type: log Xorg.DPI.log (30.7 KB, 112 views)
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Old 12-08-05, 01:05 AM   #19
aritger
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Default Re: 1.0.8174 DPI computation incorrect

Thanks for pointing that out, cozmic. It looks like you may have found a bug in the driver's EDID parser. Could you please capture the raw EDID and attach it here? You can do that either by running `startx -- -logverbose 6` or running `nvidia-settings` and then in the "Display Device" pages use the "Acquire EDID" button.

Thanks.
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Old 12-08-05, 01:13 AM   #20
Lethe
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Default Re: 1.0.8174 DPI computation incorrect

Setting the xorg option "DPI" is best for me.

Incidently, here is a good calculator:

http://www.raydreams.com/prog/dpi.aspx

You will need to measure the diagonal of your monitor though. This little tool calculated mine to 80.5 - and I found after messing that 80 is optimum, so it calculates correctly on my settings.

Nick
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Old 12-08-05, 03:09 AM   #21
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Default Re: 1.0.8174 DPI computation incorrect

Thanks all for an interesting thread. And a "Hi again" to Andy. Haven't been around for a while because, DUH, everything's been working fine! I'm grateful for your explanation, but as you can see, the logic employed in the DPI computation may need further tweaking. Regards
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Old 12-08-05, 04:26 AM   #22
cozmic
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Default Re: 1.0.8174 DPI computation incorrect

@aritger:

I have already posted the raw EDID data in this thread on page 1.
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Old 12-08-05, 07:52 AM   #23
Lethe
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Default Re: 1.0.8174 DPI computation incorrect

Quote:
Originally Posted by pete4nv
Thanks all for an interesting thread.
Yes.

I think this thread should be pinned. After fixing my DPI for my set-up, my KDE desktop has never looked so good! God knows how long it has been running incorrectly setup - and I bet a lot of people don't know about DPI either - I certainly didn't.

Nick
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Old 12-08-05, 10:43 AM   #24
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Default Re: 1.0.8174 DPI computation incorrect

The same for me

Leaving UseEdidDpi on gives for me (at a resolution of 1280x1024) a DPI of 50x50 (the fonts are nearly invisible!! ) .

Disabling UseEdidDpi gives a DPI of 75x75. Setting my DisplaySize gives a DPI of 106x106 (that is good).
I'll attach my EDID.
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File Type: zip edid.zip (264 Bytes, 102 views)
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