I am currently porting from Qt4 to Qt5. While Qt5 still provides the QGLWidget etc. classes, these are to be replaced by QOpenGLWidget etc.
Currently I am drawing complicated stuff into a framebuffer object once. Then I draw it on the screen (into the GL widget) using drawTexture() method:
target->drawTexture(rect, fb->texture());
Afterwards, I overdraw with other temporary things. So whenever I need to update the temporary stuff, I can just re-use the framebuffer object instead of redrawing the complicated stuff.
With QOpenGLWidget, as well as QOpenGLContext, however, there is no convenient drawTexture() method anymore. Drawing the texture by-hand with OpenGL would be a minimum of 20 lines of complicated stuff. Textbook stuff, I admit.
Is there any elegant/Qt way of getting my fbo contents onto the screen? For example, it is documented that QOpenGLWidget also uses an fbo as a backend. Instead of drawing the texture, we could also blit the FBOs. But how?
