Value In Brief – by Abanoub Hanna
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How to Fix (main:30677): Gtk-WARNING **: cannot open display: ?

Tutorials gtk gtk3

If you are facing this error (main:30677): Gtk-WARNING **: 05:40:47.665: cannot open display: just install Gtk+ development library, and set the display screen to 0.

Installing Gtk+ using Homebrew

If you are using a UNIX-like OS such as Mac OS X, or a Linux distribution. You can use Homebrew package manager to install Gtk+ as following.

brew install Gtk+

Install Gtk+ using apt

If you are using Debian, Ubuntu, Elementary OS, Linux Mint, .. You can use this command to install Gtk+.

sudo apt-get install libgtk-3-dev

Set DISPLAY Environment Variable

If the error persists, just run this command on terminal to set the display to the current display/monitor/screen.

export DISPLAY=":0"

If the display command fixed the error, add those lines into your .bashrc or .zshrc (according to what you are using).

if [[ -z "$DISPLAY" ]]
    export DISPLAY

Use X11 XQuartz on Mac

If your application still showing the same error on Mac OS, just install XQuartz from here and restart. Your Gtk apps will work after that.

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