Qt for Windows - Deployment

This documentation describes deployment process for Windows. We refer to the {Plug & Paint Example}{plug & paint} example application through out the document to demonstrate the deployment process.

The Windows Deployment Tool

The Windows deployment tool is designed to automate the process of creating a deployable folder containing the dependencies (libraries, QML imports, plugins, and translations) that are required to run the application from that folder. It creates a sandbox for Windows Runtime or an installation tree for Windows desktop applications, which can be easily bundled into an installation package.

The tool can be found in QTDIR/bin/windeployqt. It takes an .exe file or a directory that contains an .exe file as an argument, and scans the executable for dependencies. If a directory is passed with the --qmldir argument, windeployqt uses the qmlimportscanner tool to scan QML files inside the directory for QML import dependencies. Identified dependencies are then copied to the executable's directory. The hardcoded local paths in Qt5Core.dll are furthermore replaced with relative ones.

Additional arguments are described in the tools' help output:

  Usage: windeployqt [options] [files]
  Qt Deploy Tool 5.6.0

  The simplest way to use windeployqt is to add the bin directory of your Qt
  installation (e.g. <QT_DIR\bin>) to the PATH variable and then run:
    windeployqt <path-to-app-binary>
  If ICU, ANGLE, etc. are not in the bin directory, they need to be in the PATH
  variable. If your application uses Qt Quick, run:
    windeployqt --qmldir <path-to-app-qml-files> <path-to-app-binary>

  Options:
    -?, -h, --help             Displays this help.
    -v, --version              Displays version information.
    --dir <directory>          Use directory instead of binary directory.
    --libdir <path>            Copy libraries to path.
    --plugindir <path>         Copy plugins to path.
    --debug                    Assume debug binaries.
    --release                  Assume release binaries.
    --pdb                      Deploy .pdb files (MSVC).
    --force                    Force updating files.
    --dry-run                  Simulation mode. Behave normally, but do not
                               copy/update any files.
    --no-plugins               Skip plugin deployment.
    --no-libraries             Skip library deployment.
    --qmldir <directory>       Scan for QML-imports starting from directory.
    --no-quick-import          Skip deployment of Qt Quick imports.
    --no-translations          Skip deployment of translations.
    --no-system-d3d-compiler   Skip deployment of the system D3D compiler.
    --compiler-runtime         Deploy compiler runtime (Desktop only).
    --no-compiler-runtime      Do not deploy compiler runtime (Desktop only).
    --webkit2                  Deployment of WebKit2 (web process).
    --no-webkit2               Skip deployment of WebKit2.
    --json                     Print to stdout in JSON format.
    --angle                    Force deployment of ANGLE.
    --no-angle                 Disable deployment of ANGLE.
    --no-opengl-sw             Do not deploy the software rasterizer library.
    --list <option>            Print only the names of the files copied.
                               Available options:
                                source:   absolute path of the source files
                                target:   absolute path of the target files
                                relative: paths of the target files, relative
                                          to the target directory
                                mapping:  outputs the source and the relative
                                          target, suitable for use within an
                                          Appx mapping file
    --verbose <level>          Verbose level.

  Qt libraries can be added by passing their name (-xml) or removed by passing
  the name prepended by --no- (--no-xml). Available libraries:
  bluetooth clucene concurrent core declarative designer designercomponents
  enginio gui qthelp multimedia multimediawidgets multimediaquick network nfc
  opengl positioning printsupport qml qmltooling quick quickparticles quickwidgets
  script scripttools sensors serialport sql svg test
  websockets widgets winextras xml xmlpatterns webenginecore webengine
  webenginewidgets 3dcore 3drenderer 3dquick 3dquickrenderer 3dinput geoservices
  webchannel

  Arguments:
    [files]                    Binaries or directory containing the binary.

Static Linking

To build static applications, build Qt statically by configuring Qt with -static:

  cd C:\path\to\Qt
  configure -static <any other options you need>

If you later need to reconfigure and rebuild Qt from the same location, ensure that all traces of the previous configuration are removed by entering the build directory and running nmake distclean or mingw32-make distclean before running configure again.

Linking the Application to the Static Version of Qt

As an example, this section will build the Plug & Paint example statically.

Once Qt finishes building, build the Plug & Paint application. First we must go into the directory that contains the application:

  cd examples\tools\plugandpaint

Run qmake to create a new makefile for the application, and perform a clean build to create the statically linked executable:

  nmake clean
  qmake -config release
  nmake

You probably want to link against the release libraries, and you can specify this when invoking qmake. Now, provided that everything compiled and linked without any errors, we should have a plugandpaint.exe file that is ready for deployment. To check that the application has the required libraries, copy the executable to a machine that does not have Qt or any Qt applications installed, and run it on that machine.

Remember that if your application depends on compiler specific libraries, these must still be redistributed along with your application. You can check which libraries your application is linking against by using the depends tool. For more information, read the Application Dependencies section.

Since we cannot deploy plugins using the static linking approach, the application we have prepared is incomplete. It will run, but the functionality will be disabled due to the missing plugins. To deploy plugin-based applications we should use the shared library approach.

Shared Libraries

We have two challenges when deploying the Plug & Paint application using the shared libraries approach: The Qt runtime has to be correctly redistributed along with the application executable, and the plugins have to be installed in the correct location on the target system so that the application can find them.

Building Qt as a Shared Library

For this example, we assume that Qt is installed as a shared library, which is the default when installing Qt, in the C:\path\to\Qt directory.

Linking the Application to Qt as a Shared Library

After ensuring that Qt is built as a shared library, we can build the Plug & Paint application. First, we must go into the directory that contains the application:

  cd examples\tools\plugandpaint

Now run qmake to create a new makefile for the application, and do a clean build to create the dynamically linked executable:

  nmake clean
  qmake -config release
  nmake

This builds the core application, the following will build the plugins:

  cd ..\plugandpaint/plugins
  nmake clean
  qmake -config release
  nmake

If everything compiled and linked without any errors, we will get a plugandpaint.exe executable and the pnp_basictools.dll and pnp_extrafilters.dll plugin files.

Creating the Application Package

To deploy the application, we must make sure that we copy the relevant Qt DLLs (corresponding to the Qt modules used in the application) and the Windows platform plugin, qwindows.dll, as well as the executable to the same directory tree in the release subdirectory.

In contrast to user plugins, Qt plugins must be put into subdirectories matching the plugin type. The correct location for the platform plugin is a subdirectory named platforms. Qt Plugins section has additional information about plugins and how Qt searches for them.

If ANGLE (the default) is used, you additionally need to include both libEGL.dll and libGLESv2.dll from Qt's 'lib' directory as well as the HLSL compiler from DirectX. The HLSL compiler library, d3dcompiler_XX.dll, where XX is the version number that ANGLE (libGLESv2) was linked against.

If Qt was configured to link against ICU or OpenSSL, the respective DLL's need to be added to the release folder, too.

Note: Qt WebEngine applications have additional requirements that are listed in Deploying Qt WebEngine Applications.

Remember that if your application depends on compiler specific libraries, these must be redistributed along with your application. You can check which libraries your application is linking against by using the depends tool. For more information, see the Application Dependencies section.

We'll cover the plugins shortly, but first we'll check that the application will work in a deployed environment: Either copy the executable and the Qt DLLs to a machine that doesn't have Qt or any Qt applications installed, or if you want to test on the build machine, ensure that the machine doesn't have Qt in its environment.

If the application starts without any problems, then we have successfully made a dynamically linked version of the Plug & Paint application. But the application's functionality will still be missing since we have not yet deployed the associated plugins.

Plugins work differently to normal DLLs, so we can't just copy them into the same directory as our application's executable as we did with the Qt DLLs. When looking for plugins, the application searches in a plugins subdirectory inside the directory of the application executable.

So to make the plugins available to our application, we have to create the plugins subdirectory and copy over the relevant DLLs:

  plugins\pnp_basictools.dll
  plugins\pnp_extrafilters.dll

An archive distributing all the Qt DLLs and application specific plugins required to run the Plug & Paint application, would have to include the following files:

In addition, the archive must contain the following compiler specific libraries depending on your version of Visual Studio:

If Qt was configured to use ICU, the archive must contain:

Finally, if ANGLE was used, then the archive must additionally contain:

To verify that the application now can be successfully deployed, you can extract this archive on a machine without Qt and without any compiler installed, and try to run it.

An alternative to putting the plugins in the plugins subdirectory is to add a custom search path when you start your application using QCoreApplication::addLibraryPath() or QCoreApplication::setLibraryPaths().

  QCoreApplication::addLibraryPath("C:/some/other/path");

One benefit of using plugins is that they can easily be made available to a whole family of applications.

It's often most convenient to add the path in the application's main() function, right after the QApplication object is created. Once the path is added, the application will search it for plugins, in addition to looking in the plugins subdirectory in the application's own directory. Any number of additional paths can be added.

Manifest files

When deploying an application compiled with Visual Studio, there are some additional steps to be taken.

First, we need to copy the manifest file created when linking the application. This manifest file contains information about the application's dependencies on side-by-side assemblies, such as the runtime libraries.

The manifest file needs to be copied into the same folder as the application executable. You do not need to copy the manifest files for shared libraries (DLLs), since they are not used.

If the shared library has dependencies that are different from the application using it, the manifest file needs to be embedded into the DLL binary. Since Qt 4.1.3, the following CONFIG options are available for embedding manifests:

  embed_manifest_dll
  embed_manifest_exe

Both options are enabled by default. To remove embed_manifest_exe, add

  CONFIG -= embed_manifest_exe

to your .pro file.

You can find more information about manifest files and side-by-side assemblies at the MSDN website.

The correct way to include the runtime libraries with your application is to ensure that they are installed on the end-user's system.

To install the runtime libraries on the end-user's system, you need to include the appropriate Visual C++ Redistributable Package (VCRedist) executable with your application and ensure that it is executed when the user installs your application.

They are named vcredist_x64.exe (IA64 and 64-bit) or vcredist_x86.exe (32-bit) and can be found in the folder c{Visual Studio install path>/VC/redist/<language-code>}.

Alternatively, they can be downloaded from the web, for example vcredist_x64.exe for Visual Studio 2015.

Note: The application you ship must be compiled with exactly the same compiler version against the same C runtime version. This prevents deploying errors caused by different versions of the C runtime libraries.

Application Dependencies

Additional Libraries

Depending on configuration, compiler specific libraries must be redistributed along with your application.

For example, if Qt is built using ANGLE, its shared libraries and the HLSL compiler from DirectX to be shipped as well.

You can check which libraries your application is linking against by using the Dependency Walker tool. All you need to do is to run it like this:

  depends <application executable>

This will provide a list of the libraries that your application depends on and other information.

When looking at the release build of the Plug & Paint executable (plugandpaint.exe) with the depends tool, the tool lists the following immediate dependencies to non-system libraries:

When looking at the plugin DLLs the exact same dependencies are listed.

From Qt version 5.2 onwards, the officially supported version for OpenSSL is 1.0.0 or later. Versions >= 0.9.7 and < 1.0.0 might work, but are not guaranteed to.

Qt Plugins

All Qt GUI applications require a plugin that implements the Qt Platform Abstraction (QPA) layer in Qt 5. For Windows, the name of the platform plugin is qwindows.dll. This file must be located within a specific subdirectory (by default, platforms) under your distribution directory. Alternatively, it is possible to adjust the search path Qt uses to find its plugins, as described below.

Your application may also depend on one or more Qt plugins, such as the print support plugin, the JPEG image format plugin or a SQL driver plugin. Be sure to distribute any Qt plugins that you need with your application. Similar to the platform plugin, each type of plugin must be located within a specific subdirectory (such as printsupport, imageformats or sqldrivers) within your distribution directory.

The search path for Qt plugins is hard-coded into the QtCore library. By default, the plugins subdirectory of the Qt installation is the first plugin search path. However, pre-determined paths like the default one have certain disadvantages. For example, they may not exist on the target machine. For that reason, you need to examine various alternatives to make sure that the Qt plugins are found:

• Using qt.conf. This approach is the recommended if you have executables in different places sharing the same plugins.
• Using QApplication::addLibraryPath() or QApplication::setLibraryPaths(). This approach is recommended if you only have one executable that will use the plugin.
• Using a third party installation utility to change the hard-coded paths in the QtCore library.

If you add a custom path using QApplication::addLibraryPath it could look like this:

  QCoreApplication::addLibraryPath("C:/customPath/plugins");

Then QCoreApplication::libraryPaths() would return something like this:

• C:/customPath/plugins
• C:/Qt/%VERSION%/plugins
• E:/myApplication/directory

The executable will look for the plugins in these directories and the same order as the QStringList returned by QCoreApplication::libraryPaths(). The newly added path is prepended to the QCoreApplication::libraryPaths() which means that it will be searched through first. However, if you use QCoreApplication::setLibraryPaths(), you will be able to determine which paths and in which order they will be searched.

The How to Create Qt Plugins document outlines the issues you need to pay attention to when building and deploying plugins for Qt applications.