Docs: Move qmake-specific documentation out of Qt's documentation

This commit moves the third-party-libraries.html topic to the qmake
documentation. The topic is renamed and links to it are corrected.

See also: 623150

Task-number: QTBUG-132504
Pick-to: 6.9
Change-Id: I711400d887b7e4894021b0433eb1cd61dfdd5349
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

qmake/doc/src/qmake-manual.qdoc

@@ -39,6 +39,7 @@
         \li \l{Platform Notes}
         \li \l{qmake Language}
         \li \l{Advanced Usage}
+        \li \l{Using Third-Party Libraries}
         \li \l{Using Precompiled Headers}
         \li \l{Configuring qmake}
         \li \l{Reference}
@@ -71,7 +72,7 @@
     the information in each project file to a Makefile that executes the necessary
     commands for compiling and linking.
 
-    \section1 Describing a Project
+    \section1 Describing a project
 
     Projects are described by the contents of project (\c .pro) files. qmake
     uses the information within the files to generate Makefiles that contain
@@ -109,7 +110,7 @@
     projects. However, it might be useful, or even necessary, to use some
     platform-specific variables. For more information, see \l{Platform Notes}.
 
-    \section1 Building a Project
+    \section1 Building a project
 
     For simple projects, you only need to run qmake in the top level directory
     of your project to generate a Makefile. You can then run your platform's
@@ -121,12 +122,12 @@
     \note Add your project build directory to the list of excluded directories
       of any anti-virus application that runs on your system.
 
-    \section1 Using Third Party Libraries
+    \section1 Adding third-party libraries
 
-    The guide to \l{Third Party Libraries} shows you how to use simple third
+    The guide to \l{Using Third-Party Libraries} shows you how to use simple third
     party libraries in your Qt project.
 
-    \section1 Precompiling Headers
+    \section1 Precompiling headers
 
     In large projects, it is possible to take advantage of precompiled
     header files to speed up the build process. For more information, see
@@ -5670,3 +5671,131 @@
     added to the scope to do the same for release mode. Left as it is, the
     target name remains unmodified.
 */
+
+/*!
+    \page qmake-third-party-libraries.html
+    \title Using Third-Party Libraries
+    \brief A guide to using third party libraries with Qt and qmake
+
+    qmake allows you to use third-party libraries with Qt. 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 \c CatWhisperer,
+    and has several files that it provides as part of its library.
+    Your project, \c MyQtApp, stores these files in a folder named \c 3rdparty:
+
+    \list
+    \li MyQtApp/
+        \list
+        \li MyQtApp.pro
+        \li src/
+            \list
+            \li main.cpp
+            \endlist
+        \li 3rdparty/
+            \list
+            \li CatWhisperer
+                \list
+                \li include/
+                    \list
+                    \li CatWhisperer.h
+                    \endlist
+                \li lib/
+                    \list
+                    \li libCatWhisperer.so
+                    \li CatWhisperer.lib
+                    \endlist
+                \li bin/
+                    \list
+                    \li CatWhisperer.dll
+                    \endlist
+                \endlist
+            \endlist
+        \endlist
+    \endlist
+
+    To use the \c CatWhisperer library in \c MyQtApp, \c qmake requires the
+    location and names of the \c CatWhisperer libraries.
+    Optionally, you can also:
+
+    \list
+    \li Provide the location of the \c 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.
+    \li Choose the destination in which the \c MyQtApp executable will be
+    created.
+    \endlist
+
+    The information above is provided in the \c .pro file, so that \c 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 \c qmake expects you to provide this information.
+
+    \section1 Source Code
+
+    To be able to write
+
+    \code
+    #include <CatWhisperer.h>
+    \endcode
+
+    instead of
+
+    \code
+    #include <3rdparty/CatWhisperer/include/CatWhisperer.h>
+    \endcode
+
+    you can provide the path to the \c CatWhisperer \c include directory,
+    using the \l{qmake Variable Reference#INCLUDEPATH}{INCLUDEPATH} variable:
+
+    \code
+    INCLUDEPATH += 3rdparty/CatWhisperer/include
+    \endcode
+
+    \section1 Library Files
+
+    To let \c qmake know where to find the \c CatWhisperer library files,
+    use the \l{qmake Variable Reference#LIBS}{LIBS} variable:
+
+    \code
+    LIBS += -L"3rdparty/CatWhisperer/lib" -lCatWhisperer
+    \endcode
+
+    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:
+    \c libCatWhisperer.so and \c CatWhisperer.lib. It is not necessary
+    to specify the \c .lib extension, nor the \c lib prefix
+    (on UNIX platforms).
+
+    \section1 Destination Directory
+
+    By default, \c qmake creates the executable in the same directory as the
+    \c .pro file. We can choose our own directory using the
+    \l{qmake Variable Reference#DESTDIR}{DESTDIR} variable:
+
+    \code
+    DESTDIR = bin
+    \endcode
+
+    That's it! You can now use the \c CatWhisperer library in your project.
+    The final \c .pro file looks like this:
+
+    \code
+    TARGET = MyQtApp
+
+    TEMPLATE = app
+
+    INCLUDEPATH += 3rdparty/CatWhisperer/include
+
+    SOURCES += src/main.cpp
+
+    LIBS += -L"3rdparty/CatWhisperer/lib" -lCatWhisperer
+    \endcode
+
+    \sa {\QC: Add libraries to qmake projects}
+*/

qmake/doc/src/qmake-toc.qdoc

@@ -17,6 +17,7 @@
         \li \l{Platform Notes}
         \li \l{qmake Language}
         \li \l{Advanced Usage}
+        \li \l{Using Third-Party Libraries}
         \li \l{Using Precompiled Headers}
         \li \l{Configuring qmake}
         \li \l{Reference}