HP Prime Graphing Wireless Calculator - Manual (Page 287)

Programming in HP PPL 283
If zstring is provided, per pixel z clipping happens using
the z value string (see the following).
LINE_P returns a string that contains all the transformed
points. If you plan to call TRIANGLE or LINE multiple times
in a row using the same points and transformation, you
can do so by replacing the points_definition with this
string and omitting the transformation definition in
subsequent calls to TRIANGLE and LINE.
About zstring:
TRIANGLE_P([G]) returns a string adapted for z clipping.
To use z clipping, call TRIANGLE_P to create a z clipping
string (initialized at 255 for each pixels). You can then call
LINE_P with appropriate z (0-255) values for each of the
triangle vertices and LINE_P will not draw pixels farther
than the already drawn pixels. ZString is automatically
updated as appropriate.
PIXOFF_P
PIXOFF Syntax: PIXOFF([G], x, y)
PIXOFF_P([G], x, y)
Sets the color of the pixel G with coordinates x,y to white.
G can be any of the graphics variables and is optional.
The default is G0, the current graphic
PIXON_P
PIXON Syntax: PIXON([G], x, y [ ,color])
PIXON_P([G], x, y [ ,color])
Sets the color of the pixel G with coordinates x,y to color.
G can be any of the graphics variables and is optional.
The default is G0, the current graphic. Color can be any
color specified as #RRGGBB. The default is black.
RECT_P
RECT Syntax: RECT([G, x1, y1, x2, y2, edgecolor, fillcolor])
RECT_P([G, x1, y1, x2, y2, edgecolor, fillcolor])
Draws a rectangle on G between points x1,y1 and x2,y2
using edgecolor for the perimeter and fillcolor for the
inside.