[SOLVED] How to build the Qt + cmake + QGLWidget

Issue

I'm trying to build the simplest qt project using cmake and opengl. I created the default project and make little modification.

When I try to build the project I get 9 errors like this: main.cpp.obj:-1: error: LNK2019: ññûëêà íà íåðàçðåøåííûé âíåøíèé ñèìâîë __imp__glBegin@4 â ôóíêöèè "private: virtual void __thiscall GLWidget::paintGL(void)" (?paintGL@GLWidget@@EAEXXZ)

What should I do to build the project?

My code: CMakeLists.txt:

cmake_minimum_required(VERSION 3.5)

project(untitled2 LANGUAGES CXX)

set(CMAKE_INCLUDE_CURRENT_DIR ON)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

add_executable(untitled2
  main.cpp
)

find_package(OpenGL)

find_package(Qt5 COMPONENTS Widgets OpenGL REQUIRED)

target_link_libraries(untitled2 PRIVATE Qt5::Widgets Qt5::OpenGL)

main.cpp

#include "QApplication"
#include "QGLWidget"
#include "QDebug"
#include "cmath"

class GLWidget : public QGLWidget{
    void initializeGL(){
        /// In modelview hand is at origin
        glClearColor(1.0, 1.0, 1.0, 1.0);
    }

    void qgluPerspective(GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar){
        const GLdouble ymax = zNear * tan(fovy * 3.14 / 360.0);
        const GLdouble ymin = -ymax;
        const GLdouble xmin = ymin * aspect;
        const GLdouble xmax = ymax * aspect;
        glFrustum(xmin, xmax, ymin, ymax, zNear, zFar);
    }

    /// @note camera decides renderer size
    void resizeGL(int width, int height){
        if (height==0) height=1;
        glViewport(0,0,width,height);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        qgluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
     }

    void paintGL(){
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        glClear(GL_COLOR_BUFFER_BIT);

        glBegin(GL_POLYGON);
            glVertex2f(-0.5, -0.5);
            glVertex2f(-0.5, 0.5);
            glVertex2f(0.5, 0.5);
            glVertex2f(0.5, -0.5);
        glEnd();
    }
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    GLWidget widget;
    widget.resize(640,480);
    widget.show();
    return app.exec();
}

Solution

In Linux (Arch Linux) GLUT must be linked (use this answer as a base):

cmake_minimum_required(VERSION 3.5)

project(untitled2 LANGUAGES CXX)

set(CMAKE_INCLUDE_CURRENT_DIR ON)

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

add_executable(untitled2
  main.cpp
)

find_package(OpenGL REQUIRED)
find_package(GLUT REQUIRED)
find_package(Qt5 COMPONENTS Widgets OpenGL REQUIRED)

target_link_libraries(untitled2 PRIVATE Qt5::Widgets Qt5::OpenGL ${OPENGL_LIBRARIES} ${GLUT_LIBRARY})

Also when you include system or third-party library you must use <> instead of "" so you must change to:

#include <QApplication>
#include <QGLWidget>
#include <QDebug>
#include <cmath>
// ...

Answered By - eyllanesc

Answer Checked By - Robin (WPSolving Admin)