Qt: Difference between revisions - Official NixOS Wiki

Line 6:

This is a known issue, see {{issue|30551}} for the current status.

=== This application failed to start because it could not find or load the Qt platform plugin ??? in "" ===

==== qt4 ====

Qt4 depends on the environment variable <code>QT_PLUGIN_PATH</code> to find plugins. It is normally already

present in the environment on NixOS at least, but for example systemd user units are launched in a pretty empty environment. A solution is to use the command {{Commands|systemctl --user import-environment QT_PLUGIN_PATH}} from a sane environment. For example add it to the <code>services.xserver.displayManager.sessionCommands</code> option.

==== qt5 ====

Qt5 seems (?) to look for plugins in the <code>PATH</code>. This will fail from a systemd user unit for example, because their path is nearly empty by default. As an example, here is a workaround to have </code>usbguard-applet</code> launched from a systemd user unit:

{{File|/etc/nixos/configuration.nix|nix|<nowiki>

systemd.user.services.usbguard-applet = {

description = "USBGuard applet";

partOf = [ "graphical-session.target" ];

wantedBy = [ "graphical-session.target" ];

path = [ "/run/current-system/sw/" ]; ### Fix empty PATH to find qt plugins

serviceConfig = {

ExecStart = "${pkgs.usbguard}/bin/usbguard-applet-qt";

};

</nowiki>}}

==== Debugging methods ====

As a general rule, exporting <code>QT_DEBUG_PLUGINS=1</code> make qt print where it looks for plugins.

If a plugin exists in a directory but is ignored with a message like <code>QLibraryPrivate::loadPlugin failed on "/nix/store/...-teamspeak-client-3.1.6/lib/teamspeak/platforms/libqxcb.so" : "Cannot load library /nix/store/...-client-3.1.6/lib/teamspeak/platforms/libqxcb.so: "</code> it can be that the library cannot be <code>dlopen()</code>ed because of dependencies/rpath issues and needs <code>patchelf</code>ing. Exporting <code>LD_DEBUG=libs</code> may prove helpful in this scenario.

@@ Line 6: / Line 6: @@
 This is a known issue, see {{issue|30551}} for the current status.
+=== This application failed to start because it could not find or load the Qt platform plugin ??? in "" ===
+==== qt4 ====
+Qt4 depends on the environment variable <code>QT_PLUGIN_PATH</code> to find plugins. It is normally already
+present in the environment on NixOS at least, but for example systemd user units are launched in a pretty empty environment. A solution is to use the command {{Commands|systemctl --user import-environment QT_PLUGIN_PATH}} from a sane environment. For example add it to the <code>services.xserver.displayManager.sessionCommands</code> option.
+==== qt5 ====
+Qt5 seems (?) to look for plugins in the <code>PATH</code>. This will fail from a systemd user unit for example, because their path is nearly empty by default. As an example, here is a workaround to have </code>usbguard-applet</code> launched from a systemd user unit:
+{{File|/etc/nixos/configuration.nix|nix|<nowiki>
+  systemd.user.services.usbguard-applet = {
+    description = "USBGuard applet";
+    partOf = [ "graphical-session.target" ];
+    wantedBy = [ "graphical-session.target" ];
+    path = [ "/run/current-system/sw/" ]; ### Fix empty PATH to find qt plugins
+    serviceConfig = {
+      ExecStart = "${pkgs.usbguard}/bin/usbguard-applet-qt";
+    };
+  };
+</nowiki>}}
+==== Debugging methods ====
+As a general rule, exporting <code>QT_DEBUG_PLUGINS=1</code> make qt print where it looks for plugins.
+If a plugin exists in a directory but is ignored with a message like <code>QLibraryPrivate::loadPlugin failed on "/nix/store/...-teamspeak-client-3.1.6/lib/teamspeak/platforms/libqxcb.so" : "Cannot load library /nix/store/...-client-3.1.6/lib/teamspeak/platforms/libqxcb.so: "</code> it can be that the library cannot be <code>dlopen()</code>ed because of dependencies/rpath issues and needs <code>patchelf</code>ing. Exporting <code>LD_DEBUG=libs</code> may prove helpful in this scenario.