Device independence

Distinguishing between logical user space coordinates and physical device space coordinates

Precedence:

• ​Core Graphics​

• ​Direct2D​

• ​Java2D​

• ​Qt​

Y-coordinates: up or down?

Affects the meaning of angles, winding and rectangle parameters (top/bottom).

Precedence:

• Y-coordinates down:

  • ​Direct2D, but can be transformed​

  • ​Java 2D, but can be transformed

  • ​Qt, but can be transformed​

• Y-coordinates up:

  • ​Core Graphics, but can be transformed​

Discussion

• Pro Y-coordinates down:

  • used widely. Early APIs used it probably due to the use of CRTs.

• Pro Y-coordinates up:

  • matches convention in mathematics

Status

​open: use Y-coordinates down?