CMake Commands in Qt6 Protobuf
You should call the following CMake commands to use the Qt6::Protobuf module in your project:
find_package(Qt6 REQUIRED COMPONENTS Protobuf) target_link_libraries(mytarget PRIVATE Qt6::Protobuf)
You can use the qt_add_protobuf CMake command to implicitly call Qt Protobuf code generation for your project.
The macros usage examples:
cmake_minimum_required(VERSION 3.16...3.22) project(MyThings) find_package(Qt6 REQUIRED COMPONENTS Protobuf) qt_standard_project_setup() qt_add_protobuf(MyMessages GENERATE_PACKAGE_SUBFOLDERS PROTO_FILES path/to/message.proto path/to/other_message.proto PROTO_INCLUDES /path/to/proto/include ) qt_add_executable(MyApp main.cpp) target_link_libraries(MyApp PRIVATE MyMessages)
In the example above, we generate a library called MyMessages
, which contains the message types defined in the paths passed to the PROTO_FILES
option. The GENERATE_PACKAGE_SUBFOLDERS
option to generate a folder structure for the generated files. And the PROTO_INCLUDES
option tells protoc to look for dependencies or imports in the specified directories. We create a target for an executable called MyApp
, which we link to the MyMessages
library.
QML extended protobuf example
cmake_minimum_required(VERSION 3.16...3.22) project(MyThings) find_package(Qt6 REQUIRED COMPONENTS Protobuf Quick) qt_standard_project_setup() qt_add_protobuf(MyMessagesPlugin QML QML_URI my.messages.module.uri PROTO_FILES path/to/message.proto path/to/other_message.proto PROTO_INCLUDES /path/to/proto/include ) qt_add_protobuf(MyApp QML PROTO_FILES path/to/internal_message.proto PROTO_INCLUDES /path/to/proto/include ) qt_add_qml_module(MyApp URI example.uri VERSION 1.0 QML_FILES qml/main.qml ) qt_add_executable(MyApp main.cpp) target_link_libraries(MyApp PRIVATE Quick)
In the QML extended example above, by the first qt_add_protobuf
call, we generate a QML module called MyMessagesPlugin
, which contains the message types defined in the paths passed to the PROTO_FILES
option. We use the QML
option, that enables proto message types registration in the QML
context. The registered types will be available in QML
by importing a path that is set by the QML_URI
. By second qt_add_protobuf
call we add auto-generated code into the existing MyApp
QML module. The QML_URI
is not required in such cases. Finally, we create a target for an executable called MyApp
, which has a QML module for the graphical part and loads MyMessagesPlugin
into the main.qml file via the my.messages.module.uri
import.
Installing standalone Qt Protobuf library
The qt_add_protobuf command also produces lists of artifacts for further installation. You can read these artifacts by specifying OUTPUT_HEADERS
, and OUTPUT_TARGETS
arguments as follows:
qt_add_protobuf(MyProtoLib PROTO_FILES mylib.proto OUTPUT_HEADERS public_headers OUTPUT_TARGETS generated_targets )
The command stores the list of the header files and targets produced by the qt_add_protobuf
command to the public_headers
and generated_targets
variables accordingly.
Use the standard CMake install
command to install the artifacts and generate the config
files for your library:
include(GNUInstallDirs) set_target_properties(MyProtoLib PROPERTIES PUBLIC_HEADER "${public_headers}" INTERFACE_INCLUDE_DIRECTORIES "$<INSTALL_INTERFACE:${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_INCLUDEDIR}>" ) install(TARGETS ${generated_targets} EXPORT MyProtoLibTargets PUBLIC_HEADER DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}" ) install(EXPORT MyProtoLibTargets NAMESPACE MyProtoLib:: DESTINATION lib/cmake/MyProtoLib)
Then use the generated MyProtoLibTargets
config in the package config file. You can read more about the package creation process in the official CMake documentation.
After installation the library is available as the standalone CMake package:
find_package(Qt6 COMPONENTS Protobuf) find_package(MyProtoLib CONFIG) add_executable(MyApp main.cpp) target_link_libraries(MyApp PRIVATE MyProtoLib::MyProtoLib Qt6::Protobuf)
Note: qt_add_protobuf doesn't implicitly add Qt Protobuf
module as the transitive dependency, neither for the MyProtoLib
target nor for the MyProtoLib
CMake package. Therefore, the Qt Protobuf
module lookup and the explicit linking of MyApp
to Qt6::Protobuf
are mandatory.
See also CMake Command Reference.
Generates Qt-based C++ source code using a protobuf schema |