How to use QZXing with cmake Qt 6.4

[gween]

Hi,

I'm trying to use QZXing's encode and decode functions in my project. How does this work with cmake with Qt 6.4.0?

The latest thing I've tried is:

• Adding the qzxing directory to my project then adding the following to my base project's CMakeLists.txt

  SET(QZXING_USE_ENCODER ON)
  SET(ENABLE_ENCODER_GENERIC ON)
  SET(ENABLE_ENCODER_QR_CODE ON)
  add_subdirectory(./qzxing/src)
  

  Then, in one of my project files I #include "./qzxing/src/QZXing.h" and try to use QZXing's example in their repo:

  QString data = "text to be encoded";
  QImage barcode = QZXing::encodeData(data, QZXing::EncoderFormat_QR_CODE, QSize(width.toInt(), height.toInt()), 
  QZXing::EncodeErrorCorrectionLevel_H);
  

  I don't get any errors after adding the above, but when I try to build, I get the following error:

  :-1: error: error: undefined symbol: QZXing::encodeData(QString const&,QZXing::EncoderFormat, QSize,QZXing::EncodeErrorCorrectionLevel, bool, bool)
  

  I'm assuming that the above error is because the .cpp files aren't included with the project, so no function definitions. I haven't been able to find the correct cmake commands to do this, though (if that is the issue here).

[jsulm]

@gween You could build qzxing as a library and then link this library to your project using target_link_libraries.

[gween]

I appreciate the response @jsulm.

Does building as a library in Qt mean opening the QZXing.pro file in Qt 6.4 and clicking build? When I do so, I get the following error:

:-1: error: No rule to make target 'install'.  Stop.

What file is this install target supposed to be in?
This is the .pro file:

CONFIG += \
          enable_decoder_1d_barcodes \
          enable_decoder_qr_code \
          enable_decoder_data_matrix \
          enable_decoder_aztec \
          enable_decoder_pdf17 \
          enable_encoder_qr_code \
          #staticlib \
          #qzxing_qml \
          #qzxing_multimedia \

VERSION = 3.3

TARGET = QZXing
TEMPLATE = lib

include(QZXing-components.pri)

DEFINES -= DISABLE_LIBRARY_FEATURES

The only thing QZXing mentions about building as a library is https://github.com/ftylitak/qzxing#compile-the-project-as-an-external-library.

[jsulm]

@gween said in How to use QZXing with cmake Qt 6.4:

TEMPLATE = lib

It is already built as library.
To make it properly with QMake you should create a https://wiki.qt.io/SUBDIRS_-_handling_dependencies project. You then add qzxing as one subproject and your actualy project as another one. Then in your project you add qzxing as dependency (see "Defining Project Dependencies: .depends attributes" chapter in the link above).

[gween]

@jsulm the subdirs link you sent makes sense for QMake, but does this work with CMake since I'm using Qt 6.4? My current project doesn't have a .pro file, only a CMakeLists.txt file. Does the subdirs "pattern" apply to projects that only have CMakeLists.txt? I.e. is there a Defining Project Dependencies: .depends attributes type documentation for Qt 6.4 with cmake?

The QZXing repo does have a CMakeLists.txt file, https://github.com/ftylitak/qzxing/blob/master/src/CMakeLists.txt, in its src dir. Which is why I thought I'd just be able to add the repo as a subdirectory to my main project, then use some cmake function, such as add_subdirectory(), to reference the .h and .cpp files.

[gween]

@jsulm's answer is correct:

You could build qzxing as a library and then link this library to your project using target_link_libraries.

This was my complete misunderstanding of cmake and how it works.

# with qzxing/src copied to my project as QZXing
add_subdirectory(./QZXing/)
target_link_libraries(${PROJECT_NAME} qzxing)

My misunderstanding was from two things:

1. I thought the command add_subdirectory() was the only thing that should have been needed
2. That I had to use the library name that is specified in the QZXing/CMakeLists.txt, which, from this command add_library(qzxing "" ${SOURCES}) is qzxing.

[niqt]

@gween How do you use QZing? His CMake use QT5