Qt - Revision history

Smudgebun: Added a warning for the deprecated Qt section

2026-03-13T09:47:57Z

Added a warning for the deprecated Qt section

← Older revision		Revision as of 09:47, 13 March 2026
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	== Development ==		== Development ==
			{{warning\|With the deprecation of <code>qt5.full</code> & <code>qt6.full</code>, for 25.11 and up (see [https://github.com/NixOS/nixpkgs/blob/32b61ba4d9088ef926dd27065daad604ca6b58aa/pkgs/development/libraries/qt-6/default.nix#L152 change]) this recommendation is outdated. For now please primarily refer to the [[#Explicit Dependencies\|Explicit Dependencies]] Section below.}}

	If you want to develop qt applications in nixos you have to use nix-shell or direnv.		If you want to develop qt applications in nixos you have to use nix-shell or direnv.
	For using nix-shell just run this command in the terminal:		For using nix-shell just run this command in the terminal:

Sandro: /* Troubleshooting */

2025-11-08T04:41:30Z

Troubleshooting

← Older revision		Revision as of 04:41, 8 November 2025
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	=== This application failed to start because it could not find or load the Qt platform plugin ??? in "" ===		=== This application failed to start because it could not find or load the Qt platform plugin ??? in "" ===
	~~==== qt5 ====~~
	{{warning\|This recommendation is deprecated for 19.09 and up, see {{issue\|65399}}. Failing packages should be updated to use <code>wrapQtAppsHook</code>.}}		{{warning\|This recommendation is deprecated for 19.09 and up, see {{issue\|65399}}. Failing packages should be updated to use <code>wrapQtAppsHook</code>.}}

	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>}}~~

	~~==== qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in "" ====~~
	~~Here is a concrete example:~~

	<pre>		<pre>
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	The package will need to be fixed to use [the new https://github.com/NixOS/nixpkgs/issues/65399 <code>wrapQtAppsHook</code>]. The hook wraps every qt application with adding <code>QT_PLUGIN_PATH</code> and <code>XDG_DATA_DIRS</code> as well as <code>XDG_CONFIG_DIRS</code>.See [https://github.com/NixOS/nixpkgs/blob/nixos-19.09/pkgs/development/libraries/qt-5/hooks/wrap-qt-apps-hook.sh wrap-qt-apps-hook.sh in nixpkgs]		The package will need to be fixed to use [the new https://github.com/NixOS/nixpkgs/issues/65399 <code>wrapQtAppsHook</code>]. The hook wraps every qt application with adding <code>QT_PLUGIN_PATH</code> and <code>XDG_DATA_DIRS</code> as well as <code>XDG_CONFIG_DIRS</code>.See [https://github.com/NixOS/nixpkgs/blob/nixos-19.09/pkgs/development/libraries/qt-5/hooks/wrap-qt-apps-hook.sh wrap-qt-apps-hook.sh in nixpkgs]

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

Sandro: /* Cannot mix incompatible Qt library (version 0x_) with this library (version 0x_) */

2025-11-08T04:39:15Z

Cannot mix incompatible Qt library (version 0x_____) with this library (version 0x_____)

← Older revision		Revision as of 04:39, 8 November 2025
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	== Troubleshooting ==		== Troubleshooting ==

	~~=== Cannot mix incompatible Qt library (version 0x_____) with this library (version 0x_____) ===~~

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

	~~Starting with the 19.09 release, the issue should be fixed by {{pull\|65526}}~~

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

Sandro: /* Development */

2025-11-08T04:38:27Z

Development

← Older revision		Revision as of 04:38, 8 November 2025
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	}		}
	</syntaxHighlight>		</syntaxHighlight>

	~~Tip: if you want use clang-format, add '''clang-format''' to '''buildinputs''' list.~~

	Also create '''.envrc''' file and paste: <code>use_nix</code> into it.		Also create '''.envrc''' file and paste: <code>use_nix</code> into it.

Sandro: /* Development */

2025-11-08T04:38:01Z

Development

← Older revision		Revision as of 04:38, 8 November 2025
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	pkgs.mkShell {		pkgs.mkShell {
	buildInputs = [		buildInputs = [
	pkgs.qt5.full		pkgs.qt5.full
	pkgs.qtcreator		pkgs.qtcreator
	];		];
	}		}
	</syntaxHighlight>		</syntaxHighlight>

Sandro: /* qt4 */

2025-11-08T04:37:38Z

qt4

← Older revision		Revision as of 04:37, 8 November 2025
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	=== This application failed to start because it could not find or load the Qt platform plugin ??? in "" ===		=== 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 ====
	{{warning\|This recommendation is deprecated for 19.09 and up, see {{issue\|65399}}. Failing packages should be updated to use <code>wrapQtAppsHook</code>.}}		{{warning\|This recommendation is deprecated for 19.09 and up, see {{issue\|65399}}. Failing packages should be updated to use <code>wrapQtAppsHook</code>.}}

Tarix29: Fix syntax error in example code for specifying explitit Qt dependencies

2025-06-15T22:34:42Z

Fix syntax error in example code for specifying explitit Qt dependencies

← Older revision		Revision as of 22:34, 15 June 2025
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	However if fetching the entirety of <code>pkgs.qt6.full</code> is not appealing and you know which parts of Qt you need, your first instinct might be adding something like <code>pkgs.qt6.qtdeclarative</code> for creating QML-based Qt programs to <code>buildInputs</code>, '''however''' that will not work and you will get compile errors for missing libraries. <code>pkgs.qt6.full</code> is actually [https://github.com/NixOS/nixpkgs/blob/nixos-24.11/pkgs/development/libraries/qt-6/default.nix#L94-L144 creating an environment that contains all Qt libraries] that allows <code>qmake</code> and tools to find those libraries, so you must do the same and <code>pkgs.qt6.env</code> will help make one. For example:		However if fetching the entirety of <code>pkgs.qt6.full</code> is not appealing and you know which parts of Qt you need, your first instinct might be adding something like <code>pkgs.qt6.qtdeclarative</code> for creating QML-based Qt programs to <code>buildInputs</code>, '''however''' that will not work and you will get compile errors for missing libraries. <code>pkgs.qt6.full</code> is actually [https://github.com/NixOS/nixpkgs/blob/nixos-24.11/pkgs/development/libraries/qt-6/default.nix#L94-L144 creating an environment that contains all Qt libraries] that allows <code>qmake</code> and tools to find those libraries, so you must do the same and <code>pkgs.qt6.env</code> will help make one. For example:

	<~~syntaxHighlight~~ lang=nix>		<syntaxhighlight lang="nix">
	# shell.nix		# shell.nix
	{ pkgs ? import <nixpkgs> {} }:		{ pkgs ? import <nixpkgs> {} }:
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	# pkgs.qt6.env already includes pkgs.qt6.qtbase		# pkgs.qt6.env already includes pkgs.qt6.qtbase
	# And using `with` to prevent a lot of typing.		# And using `with` to prevent a lot of typing.
	qtEnv = with pkgs.qt6; env "qt-custom-${qtbase.version}" {		qtEnv = with pkgs.qt6; env "qt-custom-${qtbase.version}" [
	[		qtdeclarative
	qtdeclarative		];
	]
	};
	in		in
	pkgs.mkShell {		pkgs.mkShell {
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	];		];
	}		}
	</~~syntaxHighlight~~>		</syntaxhighlight>

	== Packaging ==		== Packaging ==

Jarrodsfarrell: Added a section for explicitly specifying development dependencies

2024-12-28T14:07:34Z

Added a section for explicitly specifying development dependencies

@@ Line 10: / Line 10: @@
 For using direnv, create a '''shell.nix''' file in the root of your project and paste these lines into it:
 <syntaxHighlight lang=nix>
 # shell.nix
@@ Line 27: / Line 28: @@
 Happy qt coding :)
 == Packaging ==

imported>Tobias.bora at 01:30, 18 November 2022

2022-11-18T01:30:55Z

← Older revision		Revision as of 01:30, 18 November 2022
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	== Hello world involving QML, Qt5, nix and cmake, qmake or meson ==		== Hello world involving QML, Qt5, nix and cmake, qmake or meson ==

	You can find [https://gist.github.com/tobiasBora/04d0febda0b3f09707b5e1b7b85390a5 here] a minimal example to use QML, cmake, nix and Qt5, and [https://gist.github.com/tobiasBora/6f114cca1affb5528c872ca01d7e28c1 here] is the same example with qmake instead. There is nothing special to nix there, but note that if you provide the qml file using something like <code>qrc:///main.qml</code>, then you need to write a qrc file that lists all the resources that must be included in the qt resource manager. This file is then used to compile the resources and include them in the binary (you have to compile the binaries, either automatically with cmake or qmake, or manually using rcc). With cmake you compile it using <code>qt5_add_resources(SOURCES qml.qrc)</code> ([https://doc.qt.io/qt-5/qtcore-cmake-qt5-add-resources.html doc]) as illustrated in the above example (make sure to use a variable as the source and to reuse the same variable in <code>add_executable</code>).		You can find [https://gist.github.com/tobiasBora/04d0febda0b3f09707b5e1b7b85390a5 here] a minimal example to use QML, cmake, nix and Qt5, and [https://gist.github.com/tobiasBora/6f114cca1affb5528c872ca01d7e28c1 here] is the same example with qmake instead and [https://gist.github.com/tobiasBora/812701e8741814393f3df7b23a11eb4b here] is the same with meson instead. There is nothing special to nix there, but note that if you provide the qml file using something like <code>qrc:///main.qml</code>, then you need to write a qrc file that lists all the resources that must be included in the qt resource manager. This file is then used to compile the resources and include them in the binary (you have to compile the binaries, either automatically with cmake or qmake, or manually using rcc). With cmake you compile it using <code>qt5_add_resources(SOURCES qml.qrc)</code> ([https://doc.qt.io/qt-5/qtcore-cmake-qt5-add-resources.html doc]) as illustrated in the above example (make sure to use a variable as the source and to reuse the same variable in <code>add_executable</code>).

imported>Tobias.bora at 01:29, 18 November 2022

2022-11-18T01:29:37Z

← Older revision		Revision as of 01:29, 18 November 2022
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	* [https://stackoverflow.com/questions/18663331 How to check the selected version of Qt in a .pro file?]		* [https://stackoverflow.com/questions/18663331 How to check the selected version of Qt in a .pro file?]

	== Hello world involving QML, Qt5, cmake ~~and nix~~ ==		== Hello world involving QML, Qt5, nix and cmake, qmake or meson ==

	You can find [https://gist.github.com/tobiasBora/04d0febda0b3f09707b5e1b7b85390a5 here] a minimal example to use QML, cmake, nix and Qt5, and [https://gist.github.com/tobiasBora/6f114cca1affb5528c872ca01d7e28c1 here] is the same example with qmake instead. There is nothing special to nix there, but note that if you provide the qml file using something like <code>qrc:///main.qml</code>, then you need to write a qrc file that lists all the resources that must be included in the qt resource manager. This file is then used to compile the resources and include them in the binary (you have to compile the binaries, either automatically with cmake or qmake, or manually using rcc). With cmake you compile it using <code>qt5_add_resources(SOURCES qml.qrc)</code> ([https://doc.qt.io/qt-5/qtcore-cmake-qt5-add-resources.html doc]) as illustrated in the above example (make sure to use a variable as the source and to reuse the same variable in <code>add_executable</code>).		You can find [https://gist.github.com/tobiasBora/04d0febda0b3f09707b5e1b7b85390a5 here] a minimal example to use QML, cmake, nix and Qt5, and [https://gist.github.com/tobiasBora/6f114cca1affb5528c872ca01d7e28c1 here] is the same example with qmake instead. There is nothing special to nix there, but note that if you provide the qml file using something like <code>qrc:///main.qml</code>, then you need to write a qrc file that lists all the resources that must be included in the qt resource manager. This file is then used to compile the resources and include them in the binary (you have to compile the binaries, either automatically with cmake or qmake, or manually using rcc). With cmake you compile it using <code>qt5_add_resources(SOURCES qml.qrc)</code> ([https://doc.qt.io/qt-5/qtcore-cmake-qt5-add-resources.html doc]) as illustrated in the above example (make sure to use a variable as the source and to reuse the same variable in <code>add_executable</code>).

Qt - Revision history

Smudgebun: Added a warning for the deprecated Qt section

Sandro: /* Troubleshooting */

Sandro: /* Cannot mix incompatible Qt library (version 0x_____) with this library (version 0x_____) */

Sandro: /* Development */

Sandro: /* Development */

Sandro: /* qt4 */

Tarix29: Fix syntax error in example code for specifying explitit Qt dependencies

Jarrodsfarrell: Added a section for explicitly specifying development dependencies

imported>Tobias.bora at 01:30, 18 November 2022

imported>Tobias.bora at 01:29, 18 November 2022

Sandro: /* Cannot mix incompatible Qt library (version 0x_) with this library (version 0x_) */