DPI not set or incorrectly set to 96

Bug #201032 reported by ogc on 2008-03-11
This bug affects 7 people
Affects Status Importance Assigned to Milestone
X.Org X server
linux (Ubuntu)
xorg (Ubuntu)

Bug Description

Binary package hint: xorg

xdpyinfo reports wrong screen size and dpi accordingly

reports: resolution: 108x88 dots per inch
should be and was earlier: 98x98 dpi (worked correctly in early alphas)

This seems to cause too big fonts in Firefox for me
Bug #151311 also may be related somehow

screen #0:
  dimensions: 1280x800 pixels (300x230 millimeters)
  resolution: 108x88 dots per inch

LVDS connected 1280x800+0+0 (normal left inverted right x axis y axis) 331mm x 207mm

(II) intel(0): EDID vendor "LPL", prod id 48128
(II) intel(0): EDID vendor "LPL", prod id 48128
(==) intel(0): DPI set to (96, 96)

00:00.0 Host bridge [0600]: Intel Corporation Mobile 945GM/PM/GMS, 943/940GML and 945GT Express Memory Controller Hub [8086:27a0] (rev 03)
     Subsystem: Acer Incorporated [ALI] Unknown device [1025:0090]
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller [8086:27a2] (rev 03) (prog-if 00 [VGA controller])
     Subsystem: Acer Incorporated [ALI] Unknown device [1025:0090]

ogc (hackrez) wrote :
ogc (hackrez) wrote :
ogc (hackrez) wrote :
ogc (hackrez) wrote :
ogc (hackrez) wrote :
ogc (hackrez) wrote :
Timo Aaltonen (tjaalton) wrote :

When was the previous time you upgraded the system?

Changed in xorg:
status: New → Incomplete
ogc (hackrez) wrote :

unfortunately, i can't, because i thought that this is a bug in Firefox. Maybe about 2 weeks ago, but I'm not sure

ogc (hackrez) on 2008-03-11
Changed in xorg:
status: New → Invalid

I'm forwarding a Ubuntu bug reporter's report:

xdpyinfo is reporting incorrect physical screen dimensions for a LGPhilipsLCD LP154W01-TLD (eisa: LPLbc00, edid: "LPL" prod id 48128). xrandr correctly reports the dimensions as 331mm x 207mm, and ddcprobe reports screensize: 33 21, yet xdpyinfo reports (300x230 millimeters). Xorg.0.log does not report what it took from edid in this case, but does indicate it used a 96x96 dpi.

This error causes DPI's to be set incorrectly in some applications (like Firefox). xdpyinfo is reporting the dpi to be 108x88, which may be what FF and other apps are using.

I notice that a similar monitor from this manufacturer, LGPhilipsLCD LP154W01-A5, was quirked in quirk_detailed_use_maximum_size() (bug #10304). Perhaps it simply needs a quirk for this monitor as well?


[Also see bug #15682 which has a similar problem with a different monitor and may also need this same quirk.]

Unduping and moving to xorg-server since I think this is a monitor quirking issue, not a driver issue.

Changed in xserver-xorg-video-intel:
importance: Undecided → Medium
status: Incomplete → Triaged
Changed in xorg-server:
status: Unknown → Confirmed
Bryce Harrington (bryce) on 2009-01-17
description: updated
Bryce Harrington (bryce) on 2009-01-30
description: updated

Can you please add
 Option "ModeDebug" "true"
to the Device section of /etc/X11/xorg.conf and attach the new log that you get after restarting X?

Changed in xorg-server (Ubuntu):
status: Triaged → Incomplete
ogc (hackrez) wrote :

attached log with modedebug. However this seems to be fixed at least for me, xdpyinfo reports 96x96 dpi, size still bit wrong (339x212 millimeters), although this seems to be simple calculation based on dpi, so everything is ok on Karmic.

Tormod Volden (tormodvolden) wrote :

Good. The monitor reports 331 x 207 mm (which you should be able to verify with a ruler). If that is correct, the dpi should be 1280/33.1*2.54 = 98.2 and 800/20.7*2.54 = 98.2. It seems like it uses 96x96 anyway:

(==) intel(0): DPI set to (96, 96)

Then this is back calculated to a "real" size of
1280/96*2.54 = 33.8 cm and 800/96*2.54 = 21.2 cm.

I will close the bug since your original issue has gone away, but I still wonder where the 96x96 is coming from. We used to force it in Gnome earlier, but I think not anymore.

Changed in xorg-server (Ubuntu):
status: Incomplete → Confirmed
ogc (hackrez) wrote :

Yes, physical size is about 331x207 mm, xrandr reports it correctly, xdpyinfo doesn't.

I am observing DPI set to 96. Is this the same or different bug? As the user in
I use the "intel" driver and I have an LG monitor (L1919S) attached by VGA.
In Xorg.0.log I see that the Intel reports the correct dimensions in cm for my monitor. I also have an LVDS connected monitor which is disabled in xorg.conf.

It appears this is the bug I am seeing in Lucid Lynx.
I used
Option "ModeDebug" "true"
and see the correct size read for the monitor in Xorg.0.log .
xdpyinfo reports
resolution: 96x96 dots per inch
I am also using the "intel" driver.
Setting DisplaySize in xorg.conf also has no effect.
Setting DPI by the -dpi parameter from the command line works.

This computer has 2 LCDs attached.
The LVDS monitor is disabled in xorg.conf.

It is not entirely the same, but perhaps this bug i related to Bug #201491.

I tested whether I could be observing Bug #246718. This is not.

ogc, would you please update the title to reflect that this is a more generic bug in not setting the DPI?

summary: - xorg gets wrong screen dpi on LPL id 48128
+ DPI not set or incorrectly set to 96
tags: added: lucid
Bryce Harrington (bryce) wrote :

These LPL monitors are known for having busted EDID values, I recall a number of quirks for them was added to the xserver. However since you're using kernel modesetting, I think maybe some of those quirks did not get ported over to the kernel, thus you're seeing the regression. IIRC, at one point seb128 added an override to force dpi to 96x96 in GNOME, which is why it started working.

Anyway, now that this code is in the kernel, I'm reassigning to linux. They can check if your quirk has been included in the kernel now.

Kiri, unless you have the same LPL monitor as in the original report, you should be filing a separate bug report.

affects: xorg-server (Ubuntu) → linux (Ubuntu)
Changed in linux (Ubuntu):
status: Confirmed → New
Kiri (kiri) wrote :

I have the same or related manufacturer (LG) of the LCD and graphics card.
The DPI being set is different. I notice now, his is not 96x96.
Are you saying GNOME desktop detects something and sets DPI to 96 and this may be why ogc has a different DPI and I have 96?
Do you still think a separate bug is more suitable?

Jeremy Foshee (jeremyfoshee) wrote :

Hi ogc,

Please be sure to confirm this issue exists with the latest development release of Ubuntu. ISO CD images are available from http://cdimage.ubuntu.com/releases/karmic . If the issue remains, please run the following command from a Terminal (Applications->Accessories->Terminal). It will automatically gather and attach updated debug information to this report.

apport-collect -p linux 201032

Also, if you could test the latest upstream kernel available that would be great. It will allow additional upstream developers to examine the issue. Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Once you've tested the upstream kernel, please remove the 'needs-upstream-testing' tag. This can be done by clicking on the yellow pencil icon next to the tag located at the bottom of the bug description and deleting the 'needs-upstream-testing' text. Please let us know your results.

Thanks in advance.

[This is an automated message. Apologies if it has reached you inappropriately; please just reply to this message indicating so.]

tags: added: needs-kernel-logs
tags: added: needs-upstream-testing
tags: added: kj-triage
Changed in linux (Ubuntu):
status: New → Incomplete
Sergio Callegari (callegar) wrote :

I confirm the bug on kubuntu with intel graphics.

On a DELL E6500 with a 1920x1080 15" screen. DPI should be > 100 but is set at 96.
karmic was managing resolution just right on this machine

Changed in linux (Ubuntu):
status: Incomplete → Confirmed
Changed in xorg-server:
importance: Unknown → Medium
H.i.M (hir-i-mogul-gmail) wrote :

I can confirm this bug too
Using Dell Latitude E6400 14.1", 1440*900, intel drivers, Kubuntu 10.04
DPI shoud be about 120

Wrong Monitor dimensions detected.

$ xdpyinfo | grep dimensions
  dimensions: 1440x900 pixels (381x238 millimeters)

shoud be about 306x190 millimeters. I have to manually set it:
$ xrandr --dpi 120

Maris Nartiss (maris-nartiss) wrote :

It's not a bug - it's a FEATURE! See more: https://bugs.freedesktop.org/show_bug.cgi?id=23705

Since xorg 1.7 it lies about Your screens DPI (unless You use NVIDIA closed drivers). Because Microsoft Windows up to Vista defaulted to 96dpi, now also X servers default to 96dpi no mater what screen size You have. Lucky for You, You can't override this "feature" in Your xorg.conf file.

Only option - get correct screen size settings in mm and add "xrandr --fbmm WxH" to Your .xsessionrc or set DisplaySize at Section "Monitor" in Your xorg.conf.
Be ware, that xdpyinfo also lies about Your screen size! If You use nouveau driver, it reports correct screen size and DPI in xorg.log and then this information gets ignored. Check Your screen dimensions with plain' ol' ruler to find out correct screen size.

Don't forget to inform Xorg dev's how You *love* this new feature!

Correct settings for Dell Latitude E6500 with 1440*900 screen are:
  dimensions: 1440x900 pixels (333x212 millimeters)
  resolution: 110x108 dots per inch

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