6.6 DUIM-Graphics Module
arc-to
Generic function
Summary
Draws an arc in the current path on the specified drawable.
Signature
arc-to drawable center-x center-y radius-1-dx radius-1-dy radius-2-dx radius-2-dy #key start-angle end-angle => ()
arc-to* drawable center radius-1-dx radius-1-dy radius-2-dx radius-2-dy #key start-angle end-angle => ()
Arguments
- drawable
- An instance of type
type-union(<sheet>, <medium>). - radius-1-dx
- An instance of type
<real>. - radius-1-dy
- An instance of type
<real>. - radius-2-dx
- An instance of type
<real>. - radius-2-dy
- An instance of type
<real>. - start-angle
- An instance of type
false-or(<real>). - end-angle
- An instance of type
false-or(<real>).
The following arguments are specific to arc-to.
- center-x
- An instance of type
<real>. - center-y
- An instance of type
<real>.
The following argument is specific to arc-to*.
- center
- An instance of type
<transform>.
Values
- None.
Library
duim-graphics
Module
duim-graphics
Description
Draws an arc in the current path on the specified drawable.
This function is used, in combination with line-to, curve-to, and move-to, to define a path. The function start-path should be used to start the definition of the path, and end-path can be used to finish the definition.
The center of the arc is defined by (center-x, center-y), and the extreme points of the virtual ellipse around the arc (that is, the points furthest away from the center for each radius) are calculated by adding the radius vectors radius-1-dx and radius-1-dy to center-x and center-y respectively (to calculate the outermost points for the first radius), and adding the radius vectors radius-2-dx and radius-2-dy to center-x and center-y respectively (to calculate the outermost points for the second radius).
Please note that arc-to does not currently support arcs whose orientation is not axis-aligned ellipses. For all practical purposes, this means that radius-1-dy and radius-2-dx must always be 0.
The arguments start-angle and end-angle define the extent of the arc that is drawn.
The function arc-to* is identical to arc-to, except that it passes composite objects, rather than separate coordinates, in its arguments. You should be aware that using this function may lead to a loss of performance.