arrow.md
In rswipl: Embed 'SWI'-'Prolog'

class arrow {#class-arrow}

Class arrow defines an arrow-head. Normally, arrows are connected to subclasses of class joint (class line, class arc, class path and class bezier_curve), but arrows may also be used as stand-alone graphical objects. An arrow is determined by the following parameters:

->length Distance between tip and baseline of the triangle
->wing Width of the baseline

Its orientation and position is determined by:

->tip Where the arrow-head is
->reference The arrow points to this imaginary position.

See also joint ->arrows and joint <-default_arrow.

@see class joint @see line->second_arrow @see line->first_arrow @see line->arrows

arrow<-fill: colour|{foreground,background}* If not equal to @nil, the triangle is filled with this pattern.

Defaults: @nil

@see bitmap-status
arrow-right: point Right-end of base.
arrow-left: point Computed value to speed up redraw if the parameters of the arrow has not changed.
arrow<-length: num Distance in pixels from the <-tip to the baseline of the triangle. See also <-wing.
arrow<-reference: point Imaginary point where the arrow points to. Only the direction from <-tip is considered; not the distance. <-reference and <-tip may not be at the same location.
arrow<-style: {open,closed} If open, the baseline of the triangle is not painted.
arrow<-tip: point Location of the arrow head. Together with <-reference this determines the direction into which the arrow points.
arrow<-wing: num Length of the baseline.

arrow->compute Compute -left, -right and <-area from the <-tip, <-reference, <-length and <-wing to speed up redraw.
arrow->geometry: x=[int], y=[int], width=[int], height=[int] Ignores the width and height arguments. Compares the x and y with the current <-area and moves the a arrow by calling ->points such the <-area will match the specified x and y.
arrow->initialise: length=[num], wing=[num], style=[{open,closed}], fill=[colour]* Initialise an arrow object. length is the length from the arrow-head to the back of the wing. wing is the distance between the two wing-tips. A default arrow reads the following values from associated class-variables:
```
| <-length | Tip to wing length |
| <-wing   | Wing-tip distance  |
| <-fill   | How it is filled   |
| <-style  | {open,closed}      |
```
arrow->reference_x: num Inherits description from: arrow<-reference_x
arrow->reference_y: num Inherits description from: arrow<-reference_x

arrow<-reference_y: -> num
arrow<-reference_x: -> num Directly operate on X- or Y- component of the <->reference.