Third Party Libraries
Using a third-party library with Qt is a simple process. Suppose you know of a cross-platform library that accepts audio samples of a cat's meows and translates them into English words. This library is named CatWhisperer
, and has several files that it provides as part of its library. Your project, MyQtApp
, stores these files in a folder named 3rdparty
:
- MyQtApp/
- MyQtApp.pro
- src/
- main.cpp
- 3rdparty/
- CatWhisperer
- include/
- CatWhisperer.h
- lib/
- libCatWhisperer.so
- CatWhisperer.lib
- bin/
- CatWhisperer.dll
- include/
- CatWhisperer
To use the CatWhisperer
library in MyQtApp
, qmake
requires the location and names of the CatWhisperer
libraries. Optionally, you can also:
- Provide the location of the
CatWhisperer
source code so that you don't have to type out the full path to each file when you include them in your own code. - Choose the destination in which the
MyQtApp
executable will be created.
The information above is provided in the .pro
file, so that qmake
can parse it and produce makefiles. Makefiles contain all the information needed by your compiler and linker to produce output, whether it is an executable, another library file, etc. The next sections explain the syntax with which qmake
expects you to provide this information.
Source Code
To be able to write
#include <CatWhisperer.h>
instead of
#include <3rdparty/CatWhisperer/include/CatWhisperer.h>
you can provide the path to the CatWhisperer
include
directory, using the INCLUDEPATH variable:
INCLUDEPATH += 3rdparty/CatWhisperer/include
Library Files
To let qmake
know where to find the CatWhisperer
library files, use the LIBS variable:
LIBS += -L"3rdparty/CatWhisperer/lib" -lCatWhisperer
The first part of the expression lets the linker know in which directory it should look for the library files. The double quotes are only necessary when the path contains spaces, so we could have omitted them in this example.
The second part tells the linker which libraries to link against. We have two different library files for UNIX platforms and Windows, respectively: libCatWhisperer.so
and CatWhisperer.lib
. It is not necessary to specify the .lib
extension, nor the lib
prefix (on UNIX platforms).
Destination Directory
By default, qmake
creates the executable in the same directory as the .pro
file. We can choose our own directory using the DESTDIR variable:
DESTDIR = bin
That's it! You can now use the CatWhisperer
library in your project. The final .pro
file looks like this:
TARGET = MyQtApp TEMPLATE = app INCLUDEPATH += 3rdparty/CatWhisperer/include SOURCES += src/main.cpp LIBS += -L"3rdparty/CatWhisperer/lib" -lCatWhisperer
See also qmake Manual and Qt Creator: Adding Libraries to Projects.
© 2024 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners. The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners.