How Scanline based 2d rendering engines works?

Question

Will you please provide me a reference to help me understand how scanline based rendering engines works? I want to implement a 2D rendering engine which can support region-based clipping, basic shape drawing and filling with anti aliasing, and basic transformations (Perspective, Rotation, Scaling). I need algorithms which give priority to performance rather than quality because I want to implement it for embedded systems with no fpu.