Update QGL Widget on different Thread

[miyoku157]

Hi,

Here is my problem, I'm trying to update the QGLWidget from an other thread. But when i try i got this warning:
"QOpenGLContext::swapBuffers() called without corresponding makeCurrent()"

I want to retrieve a video stream from a camera and display it on a QGLWidget. With the NVAPI, i fill one image in a GLTexture each frame. That's what i want to display. (and i have displayed it without update it in a thread)
But as i need to update it continously for the stream, i want to do it in a stream.

Here is my code:

#include "widget.h"
#include "ui_widget.h"
 
Widget::Widget(QGLWidget *parent) :
    QGLWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
}
 
Widget::~Widget()
{
 
    nv.cleanupVideo();
    th.join();
    delete ui;
}
 
void Widget::initializeGL(){
    glewInit();
//Initialize the capture of the camera
    nv = NVConfig();
    this->contextGL = wglGetCurrentContext();
    nv.GlobalInit();
    nv.LockDevice(GetDC((HWND)this->winId()),this->contextGL);
//Unbind the OpenGL context from this thread.
    wglMakeCurrent(0, 0);
//Launch the capture on an other thread
    th = std::thread(&Widget::updateGL,this);
}
 
void Widget::resizeGL(int w, int h){
    if(h==0)
        h =1;
    glViewport(0,0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    perspectiveGL(45.0f,w/h,0.1f,100.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
 
}
 
/*
* The capture will fill a GL Texture 1280*720; GL_RGBA
*
*/
void Widget::updateGL(){
//Start the capture, the previous OpenGL is bind again with 
// wglMakeCurrent(GetDC((HWND)this->winId()),this->contextGL)
    nv.StartCapture(GetDC((HWND)this->winId()),this->contextGL);
}
 
void Widget::paintGL(){
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(-1.5f,0.0f,-6.0f);
    glBegin(GL_QUADS);
    glTexCoord2f(0,1.0f);
    glVertex3f(0,0,0);
    glTexCoord2f(0,0);
    glVertex3f(0,1.0f,0);
    glTexCoord2f(1.0f,0);
    glVertex3f(1.0f,1.0f,0);
    glTexCoord2f(1.0f,1.0f);
    glVertex3f(1.0f,0,0);
    glEnd();
 
 
}
 
void Widget::perspectiveGL(GLdouble fovY, GLdouble aspect, GLdouble zNear, GLdouble zFar){
    const GLdouble pi = 3.1415926535897932384626433832795;
    GLdouble fW, fH;
    fH = tan( fovY / 360 * pi) * zNear;
    fW = fH * aspect;
    glFrustum( -fW,fW,-fH,fH,zNear,zFar);
}

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QGLWidget *parent) :
    QGLWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
}

Widget::~Widget()
{

    nv.cleanupVideo();
    th.join();
    delete ui;
}

void Widget::initializeGL(){
    glewInit();
//Initialize the capture of the camera
    nv = NVConfig();
    this->contextGL = wglGetCurrentContext();
    nv.GlobalInit();
    nv.LockDevice(GetDC((HWND)this->winId()),this->contextGL);
//Unbind the OpenGL context from this thread.
    wglMakeCurrent(0, 0);
//Launch the capture on an other thread
    th = std::thread(&Widget::updateGL,this);
}

void Widget::resizeGL(int w, int h){
    if(h==0)
        h =1;
    glViewport(0,0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    perspectiveGL(45.0f,w/h,0.1f,100.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

}

/*
* The capture will fill a GL Texture 1280*720; GL_RGBA
*
*/
void Widget::updateGL(){
//Start the capture, the previous OpenGL is bind again with 
// wglMakeCurrent(GetDC((HWND)this->winId()),this->contextGL)
    nv.StartCapture(GetDC((HWND)this->winId()),this->contextGL);
}

void Widget::paintGL(){
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(-1.5f,0.0f,-6.0f);
    glBegin(GL_QUADS);
    glTexCoord2f(0,1.0f);
    glVertex3f(0,0,0);
    glTexCoord2f(0,0);
    glVertex3f(0,1.0f,0);
    glTexCoord2f(1.0f,0);
    glVertex3f(1.0f,1.0f,0);
    glTexCoord2f(1.0f,1.0f);
    glVertex3f(1.0f,0,0);
    glEnd();


}

void Widget::perspectiveGL(GLdouble fovY, GLdouble aspect, GLdouble zNear, GLdouble zFar){
    const GLdouble pi = 3.1415926535897932384626433832795;
    GLdouble fW, fH;
    fH = tan( fovY / 360 * pi) * zNear;
    fW = fH * aspect;
    glFrustum( -fW,fW,-fH,fH,zNear,zFar);
}

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[wysota]

You need to make the GL context current to bind it to the thread. When you're done, you can release the context with a corresponding call.