Mapping physical screens to KDE containments

[Duncan]

Felix Miata posted on Tue, 19 Apr 2016 00:00:00 -0400 as excerpted:

> Duncan composed on 2016-04-19 09:29 (UTC):
> 
>> Possible side effect:  kmix's popup that normally appears in the middle
>> of the monitor I'm on when I hit the volume-up/down button on my
>> keyboard, still pops up, but is /tiny/, perhaps 16x16px, instead of the
>> normal I'd guess 256x256.
> 
> Do you have KDE forcing a DPI in systemsettings?

You mean the option in the fonts kcm?  No.

> What are your physical
> display densities, and your logical display density? Maybe an xrandr
> force of DPI (xrandr [-dpi ###,-fbmm ###X###]) at X startup would impact
> this favorably?

All three monitors are standard full-HD, 1920x1080, but they're (much) 
different sizes, 21-inch for the actual computer monitor (on 
DisplayPort-0), 42-inch (DVI-0) and 48-inch (HDMI-0) for the TV 
monitors.  FWIW I have them logically stacked to provide a fully visible 
logical 1920x324 desktop, tho the top one, the 21-inch, is physically off 
to the side, displaying a near-full-monitor superkaramba theme doing 1-
second system-status updates, with the two big ones then being my primary 
(bottom) and auxiliary (middle) workspaces.  Here's a now-dated but still 
reasonably accurate in general screenshot from 2013.

http://wstaw.org/m/2013/05/11/duncan-fullscreen.png

I don't have specific dpi (or monitor dimensions) configured anywhere, 
but xorg defaults to a standard 96x96 these days and that's what the 
Xorg.0.log says I'm set for.

It actually works out reasonably well, too, tho I use relatively huge 
fonts in the superkaramba theme to compensate for the (relatively) tiny 
size of the 21-inch monitor it's on.  For the two 40"+ monitors, tho, KDE 
systemsettings, fonts, says I'm using Noto Sans 8 for most stuff, except 
7 for small fonts and Oxygen Mono 9 for fixed.  Konsole is configured 
with FreeMono 9.  Sitting about 4 feet back, that works pretty well for 
normally full-monitor-height, half-monitor-width, windows, with my 
nearing 50-year-old eyes (contact-corrected from extreme nearsightedness, 
tho like most my age with single-vision distance correction if necessary, 
I can't read the real small stuff without either reading glasses to back 
off from the high nearsightedness correction or slipping my contact to 
the side and holding the print about six inches from my face to read it)

The 48" is ~ 41.5" horizontal -- xorg reports 105 cm, which krunner tells 
me is 41.33 inches, so its EDID is correct.  Similarly, the 21" reports 
48 cm in xorg, which is reasonably close given the 105 cm for the 48".  
But the 42" reports an entirely erroneous 160 cm, ~63 inches (it's 
actually ~37.5).  I WISH it was 63-inch horizontal!  Maybe that's what 
their biggest model running that firmware at the time was.

In terms of physical dpi, based on the horizontal, looks like the 21" is 
106 DPI, the 48" is 46 DPI, and the 42" about 52 dpi.

Meanwhile, setting xrandr -dpi 96 and restarting kmix and kwin_x11 didn't 
do anything, but restarting plasmashell *DID*, I get my big volume icons 
back again! =:^)

I did notice, however, that after restarting kwin_x11 from konsole (so it 
was logging to it), it spat out a bad drawable error (QXCBConnection: XCB 
error 9: bad drawable ...) when I tried hitting the volume control 
button.  Now spitting those out isn't unusual at all for it, as I know 
from before I set syslog-ng to filter those out, but it was interesting 
to me that in this case they were specifically linked to my pressing the 
volume-up and volume-down buttons, triggering display of that tiny (and 
empty, I didn't mention that before) window.

After restarting plasmashell and getting the full size volume notifier 
popups again, no more bad drawable errors on hitting that button!

So plasmashell, not kmix, would seem to be responsible for drawing those 
notifiers, and some resource it uses is null when it's apparently not 
seeing dpi correctly, because it apparently gets that information from 
kscreen, which I'm turning off because it seems to cause plasmashell and 
krunner so many /other/ problems.

Based on that, my guess is that on kde start I should get the big volume 
change icons until I let the monitors power down.  Once they do, I should 
get the tiny/blank icons on volume change, until I restart plasmashell.  
I'm not sure if I'll have to run xrandr -dpi 96 or not, before restarting 
the shell.  I'd guess a simple shell restart might do it, without the 
xrandr call.

So some more to test, but I did prove that restarting plasmashell, 
possibly after calling xrandr --dpi 96 (as I did in this case simply 
because I tried that before the plasmashell restart, but I don't yet know 
if it's necessary), does get me back my full size volume change icons 
after they've been lost, whether it's the monitors powering down that 
loses them or not.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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