Test for supported Qt version with CMake - qt

Question

I'm using CMake to build a Qt project, and it uses some of the newer Qt features and requires at least version 5.3 to build properly. I'd like to be nice to the people trying to build the project and fail at CMake configure time with a logical error telling them their CMake version isn't recent enough, rather than with some esoteric build error.
I know that I'll be getting at least version 5.0 by simply using the module find_package syntax (i.e. find_package(Qt5Widgets REQURIED)), but it's not so obvious how to make sure I'm using the right minor version.
What's the easiest way to do this?

Answer 1

I know this is a somewhat old post, but you can check the version using Qt5Widgets_VERSION. Here's some example CMake code:
find_package(Qt5Widgets REQUIRED)
if (Qt5Widgets_FOUND)
if (Qt5Widgets_VERSION VERSION_LESS 5.7.0)
message(FATAL_ERROR "Minimum supported Qt5 version is 5.70!")
endif()
else()
message(SEND_ERROR "The Qt5Widgets library could not be found!")
endif(Qt5Widgets_FOUND)

Answer 2

These days it is possible to pass a version to find_package, like this:
find_package(Qt5Core 5.10 REQUIRED)
The find_package call will fail if no compatible version of Qt5Core can be found:
CMake Warning at CMakeLists.txt:15 (find_package):
Could not find a configuration file for package "Qt5Core" that is
compatible with requested version "5.10".
The following configuration files were considered but not accepted:
C:/some/where/lib/cmake/Qt5Core/Qt5CoreConfig.cmake, version: 5.9.4
This is in-depth documented at https://cmake.org/cmake/help/latest/command/find_package.html#version-selection

Answer 3

There's no direct way to do this with the Qt-provided cmake packages, but it's easy enough to query the Qt version using qmake. Assuming you have something similar to the following already in the cmake files to locate the Qt install
set(QTDIR $ENV{QTDIR} CACHE STRING "Qt install path")
list(APPEND CMAKE_PREFIX_PATH ${QTDIR})
you can check the version and fail the configure step if it's too low like so
set(QT_MINIMUM_VERSION 5.3.0)
# Test for supported Qt version
find_program(QMAKE_EXECUTABLE NAMES qmake HINTS ${QTDIR} ENV QTDIR PATH_SUFFIXES bin)
execute_process(COMMAND ${QMAKE_EXECUTABLE} -query QT_VERSION OUTPUT_VARIABLE QT_VERSION)
if(QT_VERSION LESS QT_MINIMUM_VERSION)
MESSAGE(FATAL_ERROR "Minimum supported Qt version: ${QT_MINIMUM_VERSION}.
Installed version: ${QT_VERSION}")
endif()