Link:
http://labs.trolltech.com/blogs/2009/12/16/qt-graphics-and-performance-an-overview/We have two OpenGL based graphics systems in Qt. One for OpenGL 1.x, which is primarily implemented using the fixed functionality pipeline in combination with a few ARB fragment programs. It was written for desktops back in the Qt 4.0 days (2004-2005) and has grown quite a bit since. You can enable it by writing -graphicssystem opengl1 on the command line. It is currently in life-support mode, which means that we will fix critical things like crashes, but otherwise leave it be. It is not a focus for performance from our side, though it does perform quite nicely for many scenarios.
Our primary focus is the OpenGL/ES 2.0 graphics system, which is written to run on modern graphics hardware. It does not use a fixed functionality pipeline, only vertex shaders and fragment shaders. Since Qt 4.6, this is the default paint engine used for QGLWidget. Only when the required feature set is not available will we fall back to using the 1.x engine instead. When we refer to our OpenGL paint engine, its the 2.0 engine we’re talking about.
