Quartz 2D is the primary two-dimensional (2D) text and graphics rendering library: It directly supports Aqua by displaying two-dimensional graphics to create the user interface, including on-the-fly rendering and anti-aliasing. Quartz can render text with sub-pixel precision; graphics are limited to more traditional anti-aliasing, which is the default mode of operation but can be turned off. In Mac OS X 10.4 Tiger, Apple introduced Quartz 2D Extreme, enabling Quartz 2D to offload rendering to compatible GPUs. However, GPU rendering was not enabled by default due to potential video redraw issues or kernel panics.