When I boot my computer up and start X (I boot into runlevel 3 by default), sometimes my fonts all change sizes! I mean the settings stay the same (like they will all be 10 point or whatever) but "10 point" will look too small, and I'll have to go change them all to 12 point. Then, next time I boot the machine up it may change again and this time 12 point will look big so I'll have to go and change them all back to 10 point.

I am not a loony! (At least I don't think I am). This is really happening. Why am I posting it in the Slackware forum? Because I've only ever had it happen using Slackware (10.0 and 10.2 both). It seems to only happen if I use KDE (or KDM if I boot into runlevel 4).

Has anybody else experienced this? I haven't the first idea what might cause it. It is driving me up the wall!

The size of the fonts is dependent on the dpi setting.

This is determined by the startx script if you boot to runlevel 3 then issue the startx command. If you use KDM/GDM then it is determined by the settings in xorg.conf.

My "guess" is that the settings are different in each of these resulting in different font sizes depending on how you start up x, even though the font point settings stay the same.

The way to determine if this is happening is to boot each way (startx and KDM/GDM or runlevel 3 vs. runlevel 4) and issue the following command in a terminal:

xdpyinfo | grep resolution

I suspect you will get different readings depending on how you start x.

Post the results.

I always start X the same way. I don't change my default runlevel often. Anyway, next time the fonts change I will check the dpi setting. Currently it is 75x75.

Foo! It changed!

It's now 90x96 dpi. I didn't tell it to change! So what can cause that to happen?

It could be that for some reason the X-Server is not getting a response from your monitor.

This happened to me when I installed a KVM switch. Had me scratching my head for a while.

The relevant part of xorg.conf is:

Note the DisplaySize entry. It is the screen size in mm.

You can add it to your org.conf and see if it helps.

I will try that.

Oh my god! Now the fonts are bigger than ever!

It's a little more involved than just plugging in some numbers.
I'll give you some examples. I like to run at 96x96 dpi.

I have a 19 inch monitor that I usually run at 1152x864

To get 96x96 at this resolution, my settings need to be:

DisplaySize 303 228 (96 x 96 @ 1152x864)

If I am running at 1280x1024, my settings need to be:

DisplaySize 337 270 (96 x 96 @ 1280x1024)

If I want my dpi to increase to say 120x120 at a given resolution, then I would need to decrease these two numbers. The higher the dpi, the larger the fonts will be at a given point size. That's why your fonts got so huge when you used

280 210

Play with the two numbers, reboot, then check with xdpyinfo to see where you are. I would aim for 96x96 to see how you like things. Your monitor type (CRT vs Flat Panel) will make a difference as to what looks best. I say to reboot, because I have found that restarting X does not always work - YMMV.

Good luck.

I hopefully just fixed this on my computer by taking adivce from the Mozilla site
Get the dimensions from xdpyinfo (xdpyinfo | grep dimensions) and put that as your displaysize in xorg.conf.
My dimensions were 332 and 342, I placed those in and it seems to be working better now, just had to reconfig the fonts and restart KDE.

Doesn't seem to have helped, when my computer first turned on this morning it had the big huge fonts again After a quick Ctrl-Alt-Backspace it was back to "normal"
I've only noticed the fonts go crazy while using KDE. Whenever I use blackbox it doesn't seem to have the same problem.
And now I just noticed that the xdpyinfo on my monitor dimensions has changed... it's 335 and 342 now... perhaps it's a video card driver problem (running on Nvidia-1.0-8174)