old problem with QGLContext and render pixmap

[mickey]

hi, I have an old problem with render pixmap; after gen pixmap called, my textures are destroyed and I can't understand why.

//inside a member of mainForm class
QPixmap qp
qp = myWidget1->renderPixmap(800, 600, FALSE);
qi=qp.convertToImage();
qi = qi.smoothScale(500,500);
qi.save(base_file+".png","PNG");

//inside a member of mainForm class
QPixmap qp
qp = myWidget1->renderPixmap(800, 600, FALSE);
qi=qp.convertToImage();
qi = qi.smoothScale(500,500);
qi.save(base_file+".png","PNG");

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I know render pixmap do this: create a new contextGL call initializeGL(), resizeGL() an PaintGL(); after, it restore the previous context; but the previuos context is broken..also pixmap doesn't appear realistic: some textures are broken; but the texture broken on the final image image.jpg) and image on widgetGL aren't the same...
I tried to do:

myWidget1->initializeGL();
myWidget1->resizeGL(myWidget1->width(), myWidget1->height());
myWidget1->paintGL();

myWidget1->initializeGL();
myWidget1->resizeGL(myWidget1->width(), myWidget1->height());
myWidget1->paintGL();

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I thought this can see to me if some error in contextGL; but these 3 instrucion don't change the image in QGLWIdget....
After this, if I put a new texture on my image (ie on one object, so that call every gl function that initialize texttures), the prevoius context is restored and every textures are in the right place)
Help me, please; thanks

[jacek]

If I remember well, in initializeGL() you create new textures and store their IDs in member variables. If you call initializeGL() from a different context, you will loose information about textures from previous one. You must find a way to preserve those IDs between contexts (for example copy them somewhere or keep them on a stack).

[mickey]

sorry, I don't understand good but how copy it on the stack; thanks

[jacek]

I don't understand good but how copy it on the stack

If you have something like:

void GlWidget::initializeGL()
{
   ...
   _textureId = generateTexture();
   ...
}

void GlWidget::initializeGL()
{
   ...
   _textureId = generateTexture();
   ...
}

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then each time you invoke initializeGL() you will loose the previous value of _textureId member variable.

You can avoid that like this:

void GlWidget::renderPixmap(...)
{
   int oldTextureId = _textureId;   
   QPixmap result( QGLWidget::renderPixmap( ... ) );
   _textureId = oldTextureId;
   return result;
}

void GlWidget::renderPixmap(...)
{
   int oldTextureId = _textureId;   
   QPixmap result( QGLWidget::renderPixmap( ... ) );
   _textureId = oldTextureId;
   return result;
}

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[mickey]

sorry but I can't understand what's the textureID; but after I call genPixmap (now I put It inside myWidget class and don't change everythings), I call updateGL(),and everythings appear as before; then I think my way to put texture is ok.; i think is only a context problem....could you explain better what do you want to do with saving this texture ids?? thanks

[jacek]

could you explain better what do you want to do with saving this texture ids??

Could you post your initializeGL()? I might not remember your program well.

[mickey]

take it. thanks

[jacek]

What does plain.initGL() do?

[mickey]

it initialize every textures....gen tex, bind....plain it's an object and onto this I put the texture...

[jacek]

it initialize every textures....gen tex, bind....

That's the place where the problem is. Can I see it?

[mickey]

it's very complicated. Can I mail it you? thanks