MAR
2
2006

FOSDEM, DPI, KDE In London

FOSDEM at the weekend was great, there's something really exciting about having all the different Free Software communities together. As well as the KDE talks I went to see mjg59 talking about ACPI (but sadly failed to catch up with him regarding Kubuntu laptop support), the debian-installer talk, Automated Display Configuration for X and making SuSE packages. We sold out of KDE merchandise and gave out 800 Kubuntu CDs. I even managed to get a bed on the sleeper back home defeating the best efforts of the staff at Waterloo.

The X settings for dots per inch is supposed to ask your monitor how large is it and set DPI accordingly, this means a 10 point font is the same physical size on a 21" monitor and a 14" monitor. However it never really works like that since very often the monitor returns an incorrect value, or none at all, or you change your monitor, or you just like larger fonts. And most fonts are optimised to look best at 96 or 120 DPI anyway. So gnome-settings-daemon sets the DPI (of Xft) to 96, this means KDE apps suddenly change their font size as soon as your start anything which starts gnome-settings daemon. So for dapper Simon coded into Guidance to set Xft's DPI to 96 or 120 depending on what's best for your monitor. Problem solved, except for people who previously had 75 DPI in Kubuntu breezy (the fallback default for X) and changed their font sizes accordingly will now end up with fonts that are far too large, sorry folks.

For KDE Everywhere I took this photo of the K logo with Big Ben, the colour of the sky at the time caused one KDE developer to comment that it looked like an invasion of the Daleks was about to happen.

Comments

Hmm.. instead of dragging the G-folks into a proper implementation of DPI thing, Kubuntu decided to accommodate and embrace the wicked. Is it really so hard to ask the user to confirm the dimensions with a ruler?

Hard-coded DPI was a HUGE mess on Windows... why are we perpetuating the insanity?


By suslikreal at Thu, 03/02/2006 - 06:18

1. The way it is now in Kubuntu Dapper, if your Xorg DPI is greater than ~140, then the real DPI will be used, otherwise it gets rounded to 96 or 120 in the interests of getting good font rendering. 'non-standard' DPIs usually give poor font rendering on low pitch devices (less than 140 DPI). This, and making sure that no-one gets 75 DPI, is the motivation for doing this.

2. The situation now in Kubuntu has little in common with the situation on Windows. The reason why windows is a mess is because of all these applications that use hardcoded pixel based window layouts, which naturally barf if the DPI or font size is different. GTK and Qt apps (and most other X11 apps) don't suffer this problem.

3. Gnome's approach to DPI is similar to windows'. Make it configurable and let the user choose.

Unfortunately the "Right Way" doesn't work here (=hardware detection), which leaves us to at least be pragmatic.

cheers,

--
Simon


By simon edwards at Thu, 03/02/2006 - 07:44

> 'non-standard' DPIs usually give poor font rendering
> on low pitch devices (less than 140 DPI).

I'm perfectly fine with my DisplaySize-calculated 114 dpi. But maybe you're right and they would look even better with 120 dpi.

> The way it is now in Kubuntu Dapper, if your Xorg DPI
> is greater than ~140, then the real DPI will be used,
> otherwise it gets rounded to 96 or 120 in the interests
> of getting good font rendering.

I don't know exactly how it looks, but I hope there's also an option to set the xorg.conf's DisplaySize instead of going with your predifined values. So that the user at least has the choice to do it the "Right Way".


By jakob petsovits at Thu, 03/02/2006 - 09:30

I certainly hope there is such an option, or that such an option will be included in the next release of KDE. I was extremely frustrated that manually changing the dpi in xorg.conf did not change text sizes in KDE 3.5.2, as formerly in 3.4.x I had everything based around that dpi and there is no way to change font sizes such that things look the same as they used to.


By kalenedrael at Fri, 08/11/2006 - 00:51