Drawing coordinate system

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?