Inside Macintosh: QuickTime Reference

QuickDraw GX Coordinates

A coordinate space in QuickDraw GX consists of a plane in which positions are determined by coordinates. All coordinates in QuickDraw GX are specified with fixed-point numbers in the range of -32,768.0 to approximately 32,768.0. Coordinates are always written in the order (x, y), and for any coordinate space the point (0.0, 0.0) represents the origin of the space. Points that lie to the right of the origin increase in a positive direction along the x-axis; points that lie below the origin increase in a positive direction along the y-axis.

QuickDraw GX allows you to work in four coordinate spaces: geometry space, local space, global space, and device space. You can work separately in each space as appropriate; QuickDraw GX automatically converts among them when drawing. The spaces are described in order of their transformation during drawing.

Inside Macintosh: QuickTime Reference