13.3 Graphics state

The graphics-state object associated with each port holds values for parameters such as foreground , background , operation , thickness , scale-thickness , mask and font which affect graphics ports drawing to that port.

13.3.1 Setting the graphics state

The graphics state values associated with a drawing function call are set by one of three mechanisms.

Enumeration in the drawing function call. For example:

(draw-line port
 1 1 100 100

           :thickness 10

           :scale-thickness nil

           :foreground :red)

Bound using macros such as with-graphics-state. For example:

(with-graphics-state (port
 :thickness 10

                           :scale-thickness nil

                           :foreground :red)

  (draw-line port
 1 1 100 100)

  (draw-rectangle port
 2 2 40 50 :filled t))

For common cases of locally changing the transform in the graphics state, there are specific macros:

with-graphics-transform just changes the transform like with-graphics-state with :transform.
with-graphics-transform-reset allows you to ignore surrounding transformations.
with-graphics-translation, with-graphics-post-translation, with-graphics-scale and with-graphics-rotation perform commonly-used transformations.
with-graphics-mask affects specifically the masking slots.
Set by the set-graphics-state function. For example:

(set-graphics-state port
 :thickness 10

                    :scale-thickness nil

                    :foreground :red)

The first two mechanisms change the graphics state temporarily. The last one changes it permanently in port , effectively altering the "default" state.