The bug I'm about to describe is 100% reproducible on three different KDE based systems, an I7/Nvidia GPU laptop, a AMD/Nvidia desktop and a I5/Intel GPU desktop. (version details at the end of this report).

Although I have specified this bug as Dolphin it has a severe affect on the plasma desktop & panel. I find it surprising the desktop freezes when cutting & pasting, surely dolphin & plasma are different processes and shouldn't cause each other to hang ?

If you use Dolphin to CUT (copy not affected) multiple files the plasma desktop and panel freeze for a period of time. The period of time plasma freezes for is subject to the number of files being cut & pasted. If you are cutting one or two files you won't notice a problem, if you are cutting & pasting 100+ files you will see a freeze that lasts nearly 60 seconds on a I7 based system, much longer on lower powered systems. When you experience this freeze Dolphin is sending the following messages to std-err "QXcbClipboard: SelectionRequest too old"

** How to reproduce this bug **

To reproduce this bug I would first suggest you always have the plasma task panel visible, if your using auto-hide disable it, you want the panel visible at all times so you can see it freeze. In addition enable the seconds display on the digital clock that resides on the plasma panel. This allows you to see when and for how long plasma freezes.

Create two directories on the same disk/partition ie /home/bloggs/test1 and /home/bloggs/test2 as follows ..

cd /home/myusername
mkdir /home/myusername/test1 /home/myusername/test2

Then populate the directory test1 with 120 files, each 1Mbyte in size. I use the following command to do this, the size is not that important however the number of files is directly proportional to the length of time plasma hangs..

cd /home/myusername/test1
n=0;while [ $n -lt 120 ]; do dd if=/dev/urandom of=file$n bs=1M count=1;((n++));done;

Next, start dolphin from the command line so you can monitor the stdout/stderr messages it produces.

Then within dolphin, navigate to the /home/myusername/test1 directory and do a CNTRL A to select all files, then click right on the select files and select CUT (NOT COPY) and then navigate to /home/myusername/test2 and paste.

You will see the files get pasted in the view pane AND the seconds on the clock will freeze for 48 seconds (as seen on my I7 laptop).

During this time all desktop widgets freeze and clicking on any shortcuts doesn't appear to work or at least not yet, not until the freeze ends. While the desktop is frozen the files have already been cut & pasted within a second, however Dolphin is outputting over 1000 messages to stderr, all repeating "QXcbClipboard: SelectionRequest too old".

At the end of the plasma freeze all the icons you clicked on are then activated.

I varied the number of files I was cutting & pasting and found the following ..

1 to 2 file cut & paste, Dolphin DOES NOT output "QXcbClipboard: SelectionRequest too old" at all.


3 to 6 files cut and pasted. Dolphin outputs "QXcbClipboard: SelectionRequest too old" to stderr 50 times, causing plasma to freeze for about 3 seconds.

15 files cut & pasted, Dolphin outputs "QXcbClipboard: SelectionRequest too old" to stderr 129 times, causing plasma to freeze for about 6 seconds.

30 files cut & pasted, Dolphin outputs "QXcbClipboard: SelectionRequest too old" to stderr 288 times, causing plasma to freeze for about 12 seconds.

60 files cut & pasted, Dolphin outputs "QXcbClipboard: SelectionRequest too old" to stderr 566 times, causing plasma to freeze for about 24 seconds.

120 files cut & pasted, Dolphin outputs "QXcbClipboard: SelectionRequest too old" to stderr 1,169 ! times, causing Plasma to freeze for 48 seconds.

It would seem that the more files you cut & paste the longer plasma freezes for.

The systems I'm testing this on are as follows, of note is the fact this problem exists on KDE Plasma 5.12.4 (the latest stable) and on an earlier 5.8.9 and I'm assuming all version in between and possibly earlier ?

Can somebody test this using the method I've outlined above and see if you also can confirm this bug .. Thanks.

Laptop: KDE NEON LTS 5.12
8-core I72670QM@2.2GHz, 16Gbyte memory, Nvidia GTX 570M/PCIe/SSE2, Nvidia driver 4.5.0 NVIDIA 384.130, Plasma 5.12.4, KDE frameworks 5.45.0, QT version 5.9.3, kernel 4.13.0-39-generic, 64bit. Dolphin version 18.04.0.

Desktop #1: Kubuntu 16.04
8-core AMD FX 8350, 24Gbyte memory, Nvidia GT610/PCIe/SSE2, driver 4.4.0 NVIDIA 340.104, Plasma 5.8.9, frameworks 5.36.0, QT version 5.6.1, kernel 4.4.0-119-generic, 64 bit.

Desktop #2
4-core Intel i5-7400@3.00GHz, Intel Open source technology MESA DRI Intel HD Graphics 630 (Kaby Lake GT2), Plasma 5.12.4, KDE frameworks 5.45.0, QT Version 5.10.0, kernel 4.13.0-39-generic, 64 bit.