Bug 365353

Summary:	kscreen snaps to top of monitors, prevents alignment to bottom of each screen
Product:	[Plasma] KScreen	Reporter:	Paul Fee <paul.f.fee>
Component:	kcm	Assignee:	Sebastian Kügler <sebas>
Status:	RESOLVED FIXED
Severity:	normal	CC:	bernhard+kde
Priority:	NOR
Version First Reported In:	5.6.5
Target Milestone:	---
Platform:	Fedora RPMs
OS:	Linux
Latest Commit:	http://commits.kde.org/kscreen/bdaa4258090782982364ac70ac83c4035272891a	Version Fixed In:	5.7.4
Sentry Crash Report:
Attachments:	json configuration file reproducing this bug

Description Paul Fee 2016-07-11 12:25:01 UTC

I have three monitors, their resolutions are:
1. 1920x1080
2. 1920x1200
3. 1920x1080

I want to use "kcmshell5 kscreen" to arrange the monitors so that the lower edge of each monitor is aligned.  The resulting positions (as reported by xrandr) would therefore be:

1. 1920x1080+0+120
2. 1920x1200+1920+0
3. 1920x1080+3840+120

I can't achieve this using the KDE screen configuration GUI as the top of each screen is used for snapping.  This usually makes aligned easy.  However when I drag the middle screen close to the intended position, it gets snapped to the wrong position.  It seems like the top of each monitor produces a snap line, but the bottom does not.

I has to use the xrandr command to get the arrangement I desired:
$ xrandr --output DP-2 --pos 1920x-120

Reproducible: Always

Comment 1 Bernhard Scheirle 2016-08-15 22:40:00 UTC

I'm also affected by this bug.

And thanks for the xrandr command workaround.

Comment 2 Sebastian Kügler 2016-08-16 21:46:12 UTC

Created attachment 100639 [details]
json configuration file reproducing this bug

can be run from libkscreen's build directory, using the kwaylandtestserver.

Comment 3 Sebastian Kügler 2016-08-16 21:46:50 UTC

Thanks for the bug report!

I've reproduced the problem by creating a wayland server with a configuration similar to what you describe to test the systemsettings' module's ui.

It seems that there's a bug in the snapping code. I'll see if I can come up with a fix for this. 

For reference, I've attached the broken config as json file to this bug report.

Comment 4 Sebastian Kügler 2016-08-16 22:45:32 UTC

Git commit 8448070a7dc55b6719d845c4333fe9c5a35991e0 by Sebastian Kügler.
Committed on 16/08/2016 at 22:40.
Pushed by sebas into branch 'master'.

[kcm] decrease snapping area

Displays with only a small difference in size need a smaller amount of
snapping, so the user can still choose wether to top or bottom align.

This especially makes aligning monitors with 1920x1080 and 1920x1200
work.

M  +1    -1    kcm/src/declarative/qmloutput.cpp

http://commits.kde.org/kscreen/8448070a7dc55b6719d845c4333fe9c5a35991e0

Comment 5 Sebastian Kügler 2016-08-16 22:48:47 UTC

Git commit bdaa4258090782982364ac70ac83c4035272891a by Sebastian Kügler.
Committed on 16/08/2016 at 22:48.
Pushed by sebas into branch 'Plasma/5.7'.

[kcm] decrease snapping area

Displays with only a small difference in size need a smaller amount of
snapping, so the user can still choose wether to top or bottom align.

This especially makes aligning monitors with 1920x1080 and 1920x1200
work.

M  +1    -1    kcm/src/declarative/qmloutput.cpp

http://commits.kde.org/kscreen/bdaa4258090782982364ac70ac83c4035272891a