Line Items

Items of type line appear on the display as one or more connected line segments or curves. Line items support coordinate indexing operations using the canvas widget commands: dchars, index, insert. Lines are created with widget commands of the following form:

(#<widget> 'create 'line x1 y1... xn yn ?option value option value ...?)
(#<widget> 'create 'line coordList ?option value option value ...?)

The arguments x1 through yn or coordList give the coordinates for a series of two or more points that describe a series of connected line segments. After the coordinates there may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure widget commands to change the item's configuration.

The following standard options are supported by lines:

#:dash
#:activedash
#:disableddash
#:dashoffset
#:fill
#:activefill
#:disabledfill
#:stipple
#:activestipple
#:disabledstipple
#:state
#:tags
#:width
#:activewidth
#:disabledwidth

The following extra options are supported for lines:

#:arrow where

Indicates whether or not arrowheads are to be drawn at one or both ends of the line. Where must have one of the values none (for no arrowheads), first (for an arrowhead at the first point of the line), last (for an arrowhead at the last point of the line), or both (for arrowheads at both ends). This option defaults to none.

#:arrowshape shape

This option indicates how to draw arrowheads. The shape argument must be a list with three elements, each specifying a distance in any of the forms described in the COORDINATES section above. The first element of the list gives the distance along the line from the neck of the arrowhead to its tip. The second element gives the distance along the line from the trailing points of the arrowhead to the tip, and the third element gives the distance from the outside edge of the line to the trailing points. If this option isn't specified then Tk picks a ``reasonable'' shape.

#:capstyle style

Specifies the ways in which caps are to be drawn at the endpoints of the line. Style may have any of the forms accepted by Tk_GetCapStyle (butt, projecting, or round). If this option isn't specified then it defaults to butt. Where arrowheads are drawn the cap style is ignored.

#:joinstyle style

Specifies the ways in which joints are to be drawn at the vertices of the line. Style may have any of the forms accepted by Tk_GetCapStyle (bevel, miter, or round). If this option isn't specified then it defaults to miter. If the line only contains two points then this option is irrelevant.

#:smooth smoothMethod

smoothMethod must have one of the forms accepted by Tk_GetBoolean or a line smoothing method. Only bezier is supported in the core, but more can be added at runtime. If a boolean false value or empty string is given, no smoothing is applied. A boolean truth value assume bezier smoothing. It indicates whether or not the line should be drawn as a curve. If so, the line is rendered as a set of parabolic splines: one spline is drawn for the first and second line segments, one for the second and third, and so on. Straight-line segments can be generated within a curve by duplicating the end-points of the desired line segment.

#:splinesteps number

Specifies the degree of smoothness desired for curves: each spline will be approximated with number line segments. This option is ignored unless the #:smooth option is true.

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