I'm experiencing a weird problem with my desktop installation. I have an external monitor (Dell U2412M) connected via HDMI to a ThinkPad E480. The Dell monitor is configured to appear directly above the laptop display like so: The thing is that with this setup, the desktop on the laptop display (not on the external monitor) goes all flicking whenever I open any window or sometimes even without that. It's easier to show than to describe, so I've recorded a sample of the behaviour, you can watch it here.
For those who prefer to read: when I have the external monitor plugged in and configured on top of the laptop display, strange black artifacts appear on my main screen (i.e. the laptop).
What is curious about all this is that:
1. It only happens on the laptop display, never on the external monitor.
2. It only happens when the external monitor is plugged in. If I disconnect it, everything is smooth and stable.
3. It only happens when the external monitor is configured above the laptop display, as shown in the picture. I've tried placing the Dell to the side or below the laptop screen and the problem didn't show. However, changing the setup is not a solution, I like it the way it is.
4. The number of open windows doesn't seem to have any impact.
If it is of any importance, the system was installed as Beta was it released and later updated to stable, following the instructions in Linux Mint blog.
My system info:
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System: Host: ilex Kernel: 4.15.0-30-generic x86_64 bits: 64 gcc: 7.3.0 Desktop: Cinnamon 3.8.8 (Gtk 3.22.30-1ubuntu1) dm: lightdm Distro: Linux Mint 19 Tara Machine: Device: laptop System: LENOVO product: 20KN001QPB v: ThinkPad E480 serial: N/A Mobo: LENOVO model: 20KN001QPB v: SDK0J40697 WIN serial: N/A UEFI: LENOVO v: R0PET38W (1.15 ) date: 04/17/2018 Chassis: type: 10 serial: N/A Battery BAT0: charge: 47.3 Wh 99.5% condition: 47.5/45.3 Wh (105%) volts: 12.4/11.1 model: SMP 01AV446 serial: <filter>status: N/A CPU: Quad core Intel Core i5-8250U (-MT-MCP-) arch: Kaby Lake rev.10 cache: 6144 KB flags: (lm nx sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx) bmips: 14400 clock speeds: min/max: 400/3400 MHz 1: 700 MHz 2: 700 MHz 3: 700 MHz 4: 700 MHz 5: 700 MHz 6: 700 MHz 7: 700 MHz 8: 700 MHz Graphics: Card: Intel UHD Graphics 620 bus-ID: 00:02.0 chip-ID: 8086:5917 Display Server: x11 (X.Org 1.19.6 ) drivers: modesetting (unloaded: fbdev,vesa) Resolution: firstname.lastname@example.org, email@example.com OpenGL: renderer: Mesa DRI Intel UHD Graphics 620 (Kabylake GT2) version: 4.5 Mesa 18.0.5 (compat-v: 3.0) Direct Render: Yes Audio: Card Intel Sunrise Point-LP HD Audio driver: snd_hda_intel bus-ID: 00:1f.3 chip-ID: 8086:9d71 Sound: Advanced Linux Sound Architecture v: k4.15.0-30-generic Network: Card-1: Realtek RTL8111/8168/8411 PCIE Gigabit Ethernet Controller driver: r8169 v: 2.3LK-NAPI port: d000 bus-ID: 03:00.0 chip-ID: 10ec:8168 IF: enp3s0 state: down mac: <filter> Card-2: Intel Dual Band Wireless-AC 3165 Plus Bluetooth driver: iwlwifi bus-ID: 05:00.0 chip-ID: 8086:3166 IF: wlp5s0 state: up mac: <filter> Drives: HDD Total Size: 256.1GB (43.6% used) ID-1: /dev/nvme0n1 model: KXG5AZNV256G_TOSHIBA size: 256.1GB serial: <filter> firmware: 5106AALA Partition: ID-1: / size: 217G used: 89G (44%) fs: ext4 dev: /dev/dm-1 ID-2: /boot size: 705M used: 361M (56%) fs: ext4 dev: /dev/nvme0n1p2 ID-3: swap-1 size: 16.92GB used: 0.00GB (0%) fs: swap dev: /dev/dm-2 RAID: System: supported: N/A No RAID devices: /proc/mdstat, md_mod kernel module present Unused Devices: none Sensors: System Temperatures: cpu: 37.5C mobo: N/A Fan Speeds (in rpm): cpu: 12288 Repos: Active apt sources in file: /etc/apt/sources.list.d/atlassian-hipchat4.list deb https: //atlassian.artifactoryonline.com/atlassian/hipchat-apt-client artful main Active apt sources in file: /etc/apt/sources.list.d/google-chrome.list deb [arch=amd64] http: //dl.google.com/linux/chrome/deb/ stable main Active apt sources in file: /etc/apt/sources.list.d/jonathonf-vim-bionic.list deb http: //ppa.launchpad.net/jonathonf/vim/ubuntu bionic main deb-src http: //ppa.launchpad.net/jonathonf/vim/ubuntu bionic main Active apt sources in file: /etc/apt/sources.list.d/official-package-repositories.list deb http: //ftp.icm.edu.pl/pub/Linux/dist/linuxmint/packages tara main upstream import backport deb http: //ftp.agh.edu.pl/ubuntu bionic main restricted universe multiverse deb http: //ftp.agh.edu.pl/ubuntu bionic-updates main restricted universe multiverse deb http: //ftp.agh.edu.pl/ubuntu bionic-backports main restricted universe multiverse deb http: //security.ubuntu.com/ubuntu/ bionic-security main restricted universe multiverse deb http: //archive.canonical.com/ubuntu/ bionic partner Active apt sources in file: /etc/apt/sources.list.d/slack.list deb https: //packagecloud.io/slacktechnologies/slack/debian/ jessie main Info: Processes: 350 Uptime: 5:56 Memory: 6136.7/15802.7MB Init: systemd v: 237 runlevel: 5 Gcc sys: 7.3.0 Client: Unknown python3.6 client inxi: 2.3.56