Issue with QGLFunctions (Updated, now OpenGL issue)

Zamaster

So I'm trying to make a QGLWidget function with Qt Creator and I'm running into a strange issue trying to use regular OpenGL functions. My program ASSERTS and crashes with: "QGLFunctions::isInitialized(d_ptr)" in "c:\work\build\qt5_workdir\w\s\qtbase\include\qtopengl../../src/opengl/qglfunctions.h, line 722"

I found this is called from the "glGenBuffers" call in my cpp code. Ill post the .h and .cpp here:

myglwidget.h
@#ifndef MYGLWIDGET_H
#define MYGLWIDGET_H

#include <QGLWidget>
#include <QGLFunctions>
#include <QGLShaderProgram>

class MyGLWidget : public QGLWidget, protected QGLFunctions
{
Q_OBJECT
public:
explicit MyGLWidget(QWidget *parent = 0);
~MyGLWidget();

protected:
void initializeGL();
void paintGL();
void resizeGL(int width, int height);

private:
int width;
int height;
GLuint back_texture;
GLuint* vboid;
QGLShaderProgram default_prog;
};

#endif // MYGLWIDGET_H
@

myglwidget.cpp
@
#include "myglwidget.h"
#include <QDebug>
#include <QVector3D>
#include <QVector2D>
#include "locale.h"

#define BACK_TILE_S 48

struct VertexData
{
QVector3D position;
QVector2D texCoord;
};

MyGLWidget::MyGLWidget(QWidget *parent) :
QGLWidget(parent)
{
glGenBuffers(2, vboid);
}

MyGLWidget::~MyGLWidget(){
glDeleteBuffers(2, vboid);
}

void MyGLWidget::initializeGL(){
VertexData verts[] = {
{QVector3D(0, 0, 0), QVector2D(0, 0)},
{QVector3D(1, 0, 0), QVector2D(1, 0)},
{QVector3D(0, 1, 0), QVector2D(0, 1)},
{QVector3D(1, 1, 0), QVector2D(1, 1)}
};
GLushort indices[] = {
0, 1, 2, 3
};

setlocale(LC_NUMERIC, "C");

default_prog.addShaderFromSourceFile&#40;QGLShader::Vertex, ":/shaders/default.vert"&#41;;
default_prog.addShaderFromSourceFile(QGLShader::Fragment, ":/shaders/default.frag"&#41;;
default_prog.link(&#41;;

default_prog.bind(&#41;; // this is in initgl since this is the
                     // only shader we use... FOR NOW, therefore
                     // we dont have to do it elsewhere
setlocale(LC_ALL, ""&#41;;

glEnable(GL_TEXTURE_2D);
// normally here we would have the QImage buffered up already
// and would bind as needed, but again, this is the only
// texture we use for now
back_texture = bindTexture(QImage(":/gfx/gfx/back.png"));
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

glBindBuffer(GL_ARRAY_BUFFER, vboid[0]);
glBufferData(GL_ARRAY_BUFFER, 4 * sizeof(VertexData), verts, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboid[1]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, 4 * sizeof(GLushort), indices, GL_STATIC_DRAW);

}

void MyGLWidget::paintGL(){
int texw;
int texh;
QMatrix4x4 proj;
QMatrix2x2 scale;
quintptr offset;
int vertexLoc;
int texcoordLoc;

texw = (floor(width / ((double) BACK_TILE_S)) + 1);
texh = (floor(height / ((double) BACK_TILE_S)) + 1);

proj.setToIdentity();
proj.scale(texw * BACK_TILE_S, texh * BACK_TILE_S);
proj.ortho(0, width, 0, height, -1, 1);

scale.setToIdentity();
scale(0,0) = texw;
scale(1,1) = texh;

default_prog.setUniformValue("texScale", scale);
default_prog.setUniformValue("mvp_matrix", proj);
default_prog.setUniformValue("texture", 0);

glBindBuffer(GL_ARRAY_BUFFER, vboid[0]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboid[1]);

offset = 0;

vertexLoc = default_prog.attributeLocation("a_position");
default_prog.enableAttributeArray(vertexLoc);
glVertexAttribPointer(vertexLoc, 3, GL_FLOAT, GL_FALSE, sizeof(VertexData), (const void*) offset);

offset += sizeof(QVector3D);

texcoordLoc = default_prog.attributeLocation("a_texcoord");
default_prog.enableAttributeArray(texcoordLoc);
glVertexAttribPointer(texcoordLoc, 2, GL_FLOAT, GL_FALSE, sizeof(VertexData), (const void*) offset);

glDrawElements(GL_TRIANGLE_STRIP, 4, GL_UNSIGNED_SHORT, 0);

}

void MyGLWidget::resizeGL(int width, int height){
this->width = width;
this->height = height;
}
@

SGaist

Hi,

I think you are missing the call to initializeGLFunctions in your initializeGL function

Zamaster

I tried it, got more issues, (now for something completely different!) and switched to try using GLEW... now even MORE problems. It just crashes at glewInit. No reason just ends unexpectedly.

@#include <GL/glew64.h>
#include "myglwidget.h"
#include <QDebug>
#include <QVector3D>
#include <QVector2D>
#include "locale.h"

#define BACK_TILE_S 48

struct VertexData
{
QVector3D position;
QVector2D texCoord;
};

MyGLWidget::MyGLWidget(QWidget *parent) :
QGLWidget(parent)
{

}

MyGLWidget::~MyGLWidget(){
//glDeleteBuffers(2, vboid);
}

void MyGLWidget::initializeGL(){
VertexData verts[] = {
{QVector3D(0, 0, 0), QVector2D(0, 0)},
{QVector3D(1, 0, 0), QVector2D(1, 0)},
{QVector3D(0, 1, 0), QVector2D(0, 1)},
{QVector3D(1, 1, 0), QVector2D(1, 1)}
};
GLushort indices[] = {
0, 1, 2, 3
};

makeCurrent();
glewExperimental = GL_TRUE;

int glewErr = glewInit();

// if( glewErr != GLEW_OK )
// {
// qDebug("Error %s", glewGetErrorString(glewErr) ) ;
// }
/*

setlocale(LC_NUMERIC, "C");

default_prog.addShaderFromSourceFile&#40;QGLShader::Vertex, ":/shaders/default.vert"&#41;;
default_prog.addShaderFromSourceFile&#40;QGLShader::Fragment, ":/shaders/default.frag"&#41;;
default_prog.link();

default_prog.bind(); // this is in initgl since this is the
                     // only shader we use... FOR NOW, therefore
                     // we dont have to do it elsewhere
setlocale(LC_ALL, "");

glEnable(GL_TEXTURE_2D);
// normally here we would have the QImage buffered up already
// and would bind as needed, but again, this is the only
// texture we use for now
back_texture = bindTexture(QImage(":/gfx/gfx/back.png"));
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

glGenBuffers(2, vboid);

glBindBuffer(GL_ARRAY_BUFFER, vboid[0]);
glBufferData(GL_ARRAY_BUFFER, 4 * sizeof(VertexData), verts, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboid[1]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, 4 * sizeof(GLushort), indices, GL_STATIC_DRAW);
*/

}

void MyGLWidget::paintGL(){
int texw;
int texh;
QMatrix4x4 proj;
QMatrix2x2 scale;
quintptr offset;
int vertexLoc;
int texcoordLoc;

makeCurrent();


texw = (floor(width / ((double) BACK_TILE_S)) + 1);
texh = (floor(height / ((double) BACK_TILE_S)) + 1);
/*
proj.setToIdentity();
proj.scale(texw * BACK_TILE_S, texh * BACK_TILE_S);
proj.ortho(0, width, 0, height, -1, 1);

scale.setToIdentity();
scale(0,0) = texw;
scale(1,1) = texh;

default_prog.setUniformValue("texScale", scale);
default_prog.setUniformValue("mvp_matrix", proj);
default_prog.setUniformValue("texture", 0);

glBindBuffer(GL_ARRAY_BUFFER, vboid[0]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboid[1]);

offset = 0;

vertexLoc = default_prog.attributeLocation("a_position");
default_prog.enableAttributeArray(vertexLoc);
glVertexAttribPointer(vertexLoc, 3, GL_FLOAT, GL_FALSE, sizeof(VertexData), (const void*) offset);

offset += sizeof(QVector3D);

texcoordLoc = default_prog.attributeLocation("a_texcoord");
default_prog.enableAttributeArray(texcoordLoc);
glVertexAttribPointer(texcoordLoc, 2, GL_FLOAT, GL_FALSE, sizeof(VertexData), (const void*) offset);

glDrawElements(GL_TRIANGLE_STRIP, 4, GL_UNSIGNED_SHORT, 0);

*/
}

void MyGLWidget::resizeGL(int width, int height){
this->width = width;
this->height = height;
}
@

SGaist

IIRC, mixing with glew is a bad idea. Just thought about something, are you using Qt 5 ? If so you should move to the new QOpenGLXXX classes

Zamaster

Yes I am. Okay things are coming together because the man page on QGLFunctions warned against its use and I was thinking "Than what on earth am I supposed to use Qt?" So would I extend myglwidget with QOpenGLFunctions just like QGLFunctions?

Zamaster

I just tried extending to QOpenGLFunctions and I got the familiar "QOpenGLFunctions::isInitialized(d_ptr)" error.

Zamaster

Solved! had to makeCurrent() then call the similar initializeOpenGLFunctions.

Zamaster

Sooo close! But now I've run into the issue that my OpenGL code seems to flop, as in it won't draw anything but a black screen.

Updated myglwidget.cpp
@#include "myglwidget.h"
#include <QDebug>
#include <QVector3D>
#include <QVector2D>
#include "locale.h"

#define BACK_TILE_S 48

struct VertexData
{
QVector3D position;
QVector2D texCoord;
};

MyGLWidget::MyGLWidget(QWidget *parent) :
QGLWidget(parent)
{

}

MyGLWidget::~MyGLWidget(){
glDeleteBuffers(2, vboid);
}

void MyGLWidget::initializeGL(){
VertexData verts[] = {
{QVector3D(0, 0, 0), QVector2D(0, 0)},
{QVector3D(1, 0, 0), QVector2D(1, 0)},
{QVector3D(0, 1, 0), QVector2D(0, 1)},
{QVector3D(1, 1, 0), QVector2D(1, 1)}
};
GLushort indices[] = {
0, 1, 2, 3
};
makeCurrent();
initializeOpenGLFunctions();

setlocale(LC_NUMERIC, "C");

default_prog.addShaderFromSourceFile&#40;QGLShader::Vertex, ":/shaders/default.vert"&#41;;
default_prog.addShaderFromSourceFile&#40;QGLShader::Fragment, ":/shaders/default.frag"&#41;;
default_prog.link();

default_prog.bind(); // this is in initgl since this is the
                     // only shader we use... FOR NOW, therefore
                     // we dont have to do it elsewhere
setlocale(LC_ALL, "");

glDisable(GL_DEPTH_TEST);
glEnable(GL_TEXTURE_2D);
// normally here we would have the QImage buffered up already
// and would bind as needed, but again, this is the only
// texture we use for now
back_texture = bindTexture(QImage(":/gfx/gfx/back.png"));
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);


glGenBuffers(2, vboid);

glBindBuffer(GL_ARRAY_BUFFER, vboid[0]);
glBufferData(GL_ARRAY_BUFFER, 4 * sizeof(VertexData), verts, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboid[1]);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, 4 * sizeof(GLushort), indices, GL_STATIC_DRAW);

}

void MyGLWidget::paintGL(){
int texw;
int texh;
QMatrix4x4 proj;
QMatrix2x2 scale;
quintptr offset;
int vertexLoc;
int texcoordLoc;

texw = (floor(width / ((double) BACK_TILE_S)) + 1);
texh = (floor(height / ((double) BACK_TILE_S)) + 1);

proj.setToIdentity();
proj.scale(texw * BACK_TILE_S, texh * BACK_TILE_S);
proj.ortho(0, width, 0, height, -1, 1);

scale.setToIdentity();
scale(0,0) = texw;
scale(1,1) = texh;

default_prog.setUniformValue("texScale", scale);
default_prog.setUniformValue("mvp_matrix", proj);
default_prog.setUniformValue("texture", 0);

glBindBuffer(GL_ARRAY_BUFFER, vboid[0]);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vboid[1]);

offset = 0;

vertexLoc = default_prog.attributeLocation("a_position");
default_prog.enableAttributeArray(vertexLoc);
glVertexAttribPointer(vertexLoc, 3, GL_FLOAT, GL_FALSE, sizeof(VertexData), (const void*) offset);

offset += sizeof(QVector3D);

texcoordLoc = default_prog.attributeLocation("a_texcoord");
default_prog.enableAttributeArray(texcoordLoc);
glVertexAttribPointer(texcoordLoc, 2, GL_FLOAT, GL_FALSE, sizeof(VertexData), (const void*) offset);

glDrawElements(GL_TRIANGLE_STRIP, 4, GL_UNSIGNED_SHORT, 0);

}

void MyGLWidget::resizeGL(int width, int height){
this->width = width;
this->height = height;
}@

default.vert
@#version 150

uniform mat4x4 mvp_matrix;
uniform mat2x2 texScale;

in vec4 a_position;
in vec2 a_texcoord;

out vec2 v_texcoord;

void main() {
v_texcoord = a_texcoord * texScale;
gl_Position = mvp_matrix * a_position;
}
@

default.frag
@#version 150

uniform sampler2D texture;

in vec2 v_texcoord;

void main()
{
gl_FragColor = texture2D(texture, v_texcoord);
}
@

SGaist

If you are using QOpenGLFunctions you should also use QOpenGLWidget to stay within the same api

Zamaster

If only that existed yet :/

SGaist

Sorry, I've mixed it with something else, I meant QWindow

You can find an example "here":https://qt-project.org/doc/qt-5.0/qtgui/openglwindow.html