geometric pen

geometric pen (plural geometric pens)

1. An instrument for drawing geometric curves, in which the movements of a pen or pencil attached to a revolving arm of adjustable length may be indefinitely varied by changing the toothed wheels which give motion to the arm.
   • 1797, Colin Macfarquhar, George Gleig, Encyclopædia Britannica, page 116:

     But it may be proper to take some notice of the geometric pen, as it is not so well known , nor the principles on which it depends so obvious .

   • 1829, Mechanics' Magazine, Museum, Register, Journal, and Gazette:

     The geometric pen and geometric chuck, in point of mechanical contrivance, are necessarily as different as two instruments, giving to a certain extend similar results, can possibly be; and they act upon diametrically opposite principles;

2. (computer graphics) A configurable drawing tool for creating lines that has a width specified in logical units, as opposed to device units (pixels), and therefore scales when the resulting image is zoomed in or out.
   • 1994 January 25, Charles Petzold, “Extended Pen Creation Under Windows NT”, in PC Magazine, volume 13, number 2, page 291:

     The classic example of using geometric and cosmetic pens is in architectural drawing: You'd use a geometric pen for drawing the walls of the building. If you then zoom in on the drawing using a transform, the walls will appear wider, as they should.

   • 2001, Feng Yuan, Windows Graphics Programming: Win32 GDI and DirectDraw, page 468:

     To be more specific, a geometric pen has a scalable width, different styles, end caps, and joins.