What is the purpose of the *.pro file?

The *.pro file is a configuration file commonly used in projects built with Qt, a popular framework for developing cross-platform applications. The file plays a crucial role in defining the build settings for the project and is processed by the Qt qmake tool, which generates the appropriate platform-specific build files (e.g., Makefiles or Visual Studio project files).

Purpose of the *.pro File

The *.pro file serves the following purposes:

1. Specifies Project Information:
   • Name, version, and target information for the project.
   • Example:

     TARGET = MyApplication
     TEMPLATE = app
     

2. Defines Source and Header Files:
   • Lists the files to be included in the build process.
   • Example:

     SOURCES += main.cpp myclass.cpp
     HEADERS += myclass.h
     

3. Manages Resources:
   • Adds resource files like images, icons, and other assets.
   • Example:

     RESOURCES += resources.qrc
     

4. Specifies Dependencies:
   • Includes Qt modules (e.g., QtCore, QtGui, QtWidgets) and other libraries.
   • Example:

     QT += core gui widgets
     

5. Customizes Build Settings:
   • Enables customization of compiler flags, include paths, library paths, and more.
   • Example:

     INCLUDEPATH += ./include
     LIBS += -L/usr/lib -lmylibrary
     

6. Handles Platform-Specific Configurations:
   • Allows specifying settings for different operating systems or build environments.
   • Example:

     win32 {
         LIBS += -lwindowslibrary
     }
     unix {
         LIBS += -lunixlibrary
     }
     

7. Supports Translation Files:
   • Adds translation files for internationalization (i18n).
   • Example:

     TRANSLATIONS += myapp_en.ts myapp_fr.ts
     

Common Sections in a *.pro File

Below is a breakdown of typical sections:

1. Project Basics:

   TEMPLATE = app      # Type of project: app, lib, etc.
   TARGET = myapp      # Output name
   

2. Source and Header Files:

   SOURCES += main.cpp myclass.cpp
   HEADERS += myclass.h
   

3. Resources:

   RESOURCES += resources.qrc
   

4. Qt Modules:

   QT += core gui widgets
   

5. Compiler and Linker Flags:

   CONFIG += c++17 debug
   

How Does It Work?

1. You write a .pro file to define the build settings for your project.
2. The qmake tool processes the .pro file to generate platform-specific build files.
   • On Linux, it creates a Makefile.
   • On Windows, it creates .vcxproj files for Visual Studio.
3. You then use the generated build files to compile and run your project.

Example *.pro File

Here’s a simple example for a Qt GUI application:

QT += core gui widgets

TEMPLATE = app
TARGET = MyQtApp

SOURCES += main.cpp mainwindow.cpp
HEADERS += mainwindow.h
RESOURCES += icons.qrc

CONFIG += c++17 debug

This .pro file specifies:

• The use of core, GUI, and widget modules.
• The application’s source and header files.
• A resource file (icons.qrc).
• The use of C++17 with debugging enabled.

Duplicate Note

This might be a frequently asked question in Qt communities because the .pro file is an essential component for building and configuring projects. The purpose and usage often need clarification for newcomers or those transitioning from other build systems.