OpenGL, Shaders, and GLSL
The Open Graphics Library (OpenGL) is a programming library that handles 2D as well as 3D graphics. OpenGL works on all major desktop operating systems and there is also a version that works on mobile devices, known as OpenGL ES.
OpenGL was originally released in 1992. It has been refined and improved over more than twenty years. Furthermore, graphics card manufacturers design their hardware to make it work well with OpenGL. The point of mentioning this is not for the history lesson but to explain that it would be a fool's errand to try and improve upon OpenGL and use it in 2D (and 3D games) on the desktop, especially if we want our game to run on more than just Windows, which is the obvious choice. We are already using OpenGL because SFML uses OpenGL. Shaders are programs that run on the GPU itself. We'll find out more about them in the following section.
The programmable pipeline and shaders
Through OpenGL, we have access to what is called...
