how to draw OpenGL geometry in Qt 5.7 using glew - c++

Question

I am trying to render a triangle in a QGLWidget (Qt5.7) but by some reason, I am unable to show the triangle on screen, only the blue background is showed.
myapp.pro file:
QT += core gui opengl
CONFIG += c++11
TARGET = myapp
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
INCLUDEPATH += ../../libs/glew/include
SOURCES += main.cpp \
../../libs/glew/src/glew.c \
glwindow.cpp
HEADERS += \
../../libs/glew/include/GL/glew.h \
glwindow.h
This is the main function:
#include <QApplication>
#include <glwindow.h>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
glwindow v;
v.show();
return app.exec();
}
The window header:
#include <QtOpenGL/QGLWidget>
class glwindow : public QGLWidget
{
public:
glwindow();
protected:
void initializeGL() override;
void paintGL() override;
};
The cpp file:
#include <GL/glew.h>
#include <glwindow.h>
GLfloat vertices[] = {
+0.0f, +1.0f,
-1.0f, -1.0f,
+1.0f, -1.0f
};
glwindow::glwindow()
{}
void setupGeometry()
{
GLuint buffer_id;
glGenBuffers(1, &buffer_id);
glBindBuffer(GL_ARRAY_BUFFER, buffer_id);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);
}
void glwindow::initializeGL()
{
glewInit();
setupGeometry();
}
void glwindow::paintGL()
{
glClearColor(0.0, 0.0, 1.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, 3);
}
Update 1:
Added the shader code:
const GLchar *vs = "#version 150 // Specify which version of GLSL we are using."
"in vec2 in_Position;"
"void main() "
"{"
" gl_Position = vec4(in_Position.x, in_Position.y, 0.5, 1.0);"
"}";
const GLchar *fs = "#version 150 // Specify which version of GLSL we are using."
"precision highp float; // Video card drivers require this line to function properly"
"out vec4 fragColor;"
"void main()"
"{"
" fragColor = vec4(1.0,1.0,1.0,1.0); //Set colour of each fragment to WHITE"
"}";
The function that setup shader is:
void checkShader(GLuint ID)
{
GLint compile_status = 0;
glGetShaderiv(ID, GL_COMPILE_STATUS, &compile_status);
if(compile_status != GL_TRUE)
{
GLint info_length;
GLsizei buffer_size;
glGetShaderiv(ID, GL_INFO_LOG_LENGTH, &info_length);
GLchar *message = new GLchar[info_length];
glGetShaderInfoLog(ID, info_length, &buffer_size, message);
delete[] message;
}
}
void initShader()
{
GLuint program_id;
GLuint vs_id, fs_id;
vs_id = glCreateShader(GL_VERTEX_SHADER);
fs_id = glCreateShader(GL_FRAGMENT_SHADER);
const char *adapter[1];
adapter[0] = vs;
glShaderSource(vs_id, 1, adapter, 0);
adapter[1] = fs;
glShaderSource(fs_id, 1, adapter, 0);
glCompileShader(vs_id);
checkShader(vs_id);
glCompileShader(fs_id);
checkShader(fs_id);
program_id = glCreateProgram();
glAttachShader(program_id, vs_id);
glAttachShader(program_id, fs_id);
glLinkProgram(program_id);
glUseProgram(program_id);
}
So, the init function is changed to
void glview::initializeGL()
{
glewInit();
initGeometry();
initShader();
}
The shader initialization is failed with error message :
(GLchar *) 0x7efe21 \":1(10): error: GLSL 1.50 is not supported. Supported versions are: 1.10, 1.20, 1.30, 1.00 ES, and 3.00 ES\n\"

Answer 1

Qt 5.7 only supports to glsl 1.3.0. So if ppl want to use glsl 4.3, try glfw or SDL.