10min programming

8. opengl 测试

最简单的opengl程序，简单到什么都不显示。glut负责opengl的窗口管理，greeglut是glut的一个实现，官方的实现已经不再更新了，现在基本上都用freeglut。

#include<GL/freeglut.h>int main(int argc, char** argv){glutInit(&argc, argv);glutMainLoop();return 0;}

CMakeLists.txt

cmake_minimum_required(VERSION 2.8.11)project(gl_test)find_package(GLUT REQUIRED)add_executable(${PROJECT_NAME} main.cpp)target_include_directories(${PROJECT_NAME} PUBLIC ${GLUT_INCLUDE_DIR})target_link_libraries(${PROJECT_NAME} ${GLUT_LIBRARIES})

7. BLAS(ATLAS)+cmake

用到cblas的测试程序。ATLAS是BLAS的一个实现。

#include<iostream>#include<cblas.h>int main(int argc, char** argv){    double a[3] = {1.0, 2.0, 3.0};    double b[3] = {4.0, 5.0, 6.0};    double c = cblas_ddot(3, a, 1, b, 1);  std::cout<<"get "<<c<<std::endl;    return 0;}

cmake_minimum_required(VERSION 2.8.11)project(atlas_test)find_package(BLAS REQUIRED)add_executable(${PROJECT_NAME} main.cpp)target_include_directories(${PROJECT_NAME} PUBLIC ${ATLAS_INCLUDE_DIR})target_link_libraries(${PROJECT_NAME} ${BLAS_atlas_LIBRARY} ${BLAS_f77blas_LIBRARY} /usr/lib/libblas.so)

cmake自带的find模块没能找到 libblas.so ，要手动加进去

6. opencv3+cmake

opencv3 sample main.cpp

#include<iostream>#include<opencv2/opencv.hpp>int main(int argc, char** argv){    if(argc < 2){        std::cout << "usage: command [your_image_file]" << std::endl;    }        cv::Mat img=cv::imread(argv[1]);    if(!img.data){        std::cout<<"No image data"<<std::endl;        return -1;    }    cv::namedWindow("ImgWin");    cv::imshow("ImgWin", img);    cv::waitKey(0);    return 0;}

CMakeLists.txt

cmake_minimum_required(VERSION 2.8.11)project(opencv3_test)find_package(OpenCV REQUIRED)include_directories( ${OpenCV_INCLUDE_DIRS})add_executable( ${PROJECT_NAME} main.cpp )target_link_libraries(${PROJECT_NAME} ${OpenCV_LIBS})

pacakge 名就是 OpenCV，不加版本号...

5. qt5+cmake

CMakeLists.txt

需要两个set, 在target_link_libraries添加Qt5::<ModuelName>, 不用添加 target_include_directories(...) 

cmake_minimum_required(VERSION 2.8.11)project(qt5_cmake)set(CMAKE_INCLUDE_CRUURENT_DIR ON)set(CMAKE_AUTOMOC ON)# find_package(Qt5 REQUIRED COMPONENTS Widgets)find_package(Qt5Widgets REQUIRED)add_executable(${PROJECT_NAME} main.cpp)target_link_libraries(${PROJECT_NAME} Qt5::Widgets)

简单的 main.cpp

#include <QApplication>#include <QMainWindow>int main(int argc, char** argv){QApplication app(argc, argv);QMainWindow mainWin;mainWin.show();return app.exec();}

4. call the C++ function in a library from python

如果是只调用函数，不涉及类，可以ctypes, 参考

http://stackoverflow.com/questions/23724417/how-to-call-c-functions-of-a-class-from-a-python

http://stackoverflow.com/questions/145270/calling-c-c-from-python

from ctypes import *cpp_test_lib_func =cdll.LoadLibrary('../test_lib/libtest_lib.so').test_lib_funccpp_test_lib_func()

使用boost

借助 boost.python 从python调用c++，首先要用BOOST_PYTHON_MODULE指定导出的包名等，然后编译时链接 boost.python 库，就可以在python里直接使用了。

#include "test_lib.h"#include <iostream>#include <boost/python.hpp>void test_lib_func(void){std::cout<< "hello, test_lib func" << std::endl;return;}BOOST_PYTHON_MODULE(test_lib){boost::python::def("test_lib_func", test_lib_func);}

可以参考 http://stackoverflow.com/questions/5851016/boost-python-and-cmake-link-and-load-errors?rq=1

使用SWIG？

http://www.swig.org/Doc3.0/Python.html#Python_nn2

3. write a program + a library and use cmake to configure

首先写库文件，将库命名为 test_lib

test_lib.h

#ifndef TEST_LIB_H#define TEST_LIB_Hvoid test_lib_func(void);#endif

test_lib.cpp

#include "test_lib.h"#include <iostream>void test_lib_func(void){    std::cout<< "hello, test_lib func" << std::endl;    return;}

test_lib 中的 CMakeLists.txt

cmake_minimum_required(VERSION 2.8.11)add_library(test_lib test_lib.h test_lib.cpp)

test_lib中的 test_libConfig.txt

set( test_lib_FOUND TRUE )find_path(test_lib_INCLUDES test_lib.h PATHS ${test_lib_DIR}) find_library(test_lib_LIB test_libPATHS ${test_lib_DIR})

主程序，命名为 app

main.cpp

#include <iostream>#include "test_lib.h"int main( void ){    std::cout << "Test" << std::endl;    test_lib_func(); // test function in test_lib library    return 0;}

app中的CMakeLists.txt

cmake_minimum_required(VERSION 2.8.11)project(app)find_package( test_lib REQUIREDPATHS ../test_lib)add_executable(app main.cpp ${test_lib_INCLUDES}/test_lib.h)target_include_directories(app PUBLIC ${test_lib_INCLUDES})target_link_libraries(app ${test_lib_LIB})

在编写的时候要注意的地方： 

a.  target_include_directories 和 include_libraries 不同的是 scope 不同，前者只对target，后者的scope是后面以及子文件夹中的部分

b. 在用到变量引用时，要使用${变量}

c. 在find_package处理中使用find_path和find_library分别寻找包含目录和库文件

另外在 add_library(...) 函数中添加关键词 SHARED 可以生成动态链接库

linux 只能在环境变量和编程时设置的路径里找动态链接库.so？

2. separate Debug and Release build folder

dir

--src

--build

----Debug

----Release

run_cmake.sh

cd ./build/Debugcmake -DCMAKE_BUILD_TYPE=Debug ../../srccd ../Releasecmake -DCMAKE_BUILD_TYPE=Release ../../src

但是生成的两个 makefile 几乎是一样的，最后为什么会一个是Debug，一个是 Release?

gdb

breakpoint mainrunn...

1.  write a 'hello world' program

linux + vim + qmake

qt main:

.pro file:

qmakemake

replace qmake with cmake. cmake script follows