Provided by: tklib_0.6-1_all 
NAME
canvas::edit::polyline - Editing a polyline on a canvas
SYNOPSIS
package require Tcl 8.5
package require Tk 8.5
package require canvas::edit::points ?0.1?
package require canvas::edit::polyline ?0.1?
::canvas::edit polyline objectName canvas options...
objectName destroy
objectName enable
objectName disable
objectName active
objectName add x y
objectName clear
createCmd canvas x y
highlightCmd on canvas item
highlightCmd off canvas state
dataCmd editorObj coordinates
_________________________________________________________________
DESCRIPTION
This package provides a class whose instances handle editing a single poly-line on a
canvas. Instances can be configured with regard to the visual appearance (regular, and
highlighted) of the markers denoting the line's vertices. Note that instances do not store
the edited polyline themselves, but delegate this to a configurable object.
CLASS API
::canvas::edit polyline objectName canvas options...
This, the class command, creates and configures a new instance of a polyline
editor, named objectName. The instance will be connected to the specified canvas
widget.
The result of the command is the fully qualified name of the instance command.
The options accepted here, and their values, are explained in the section Options.
INSTANCE API
Instances of the polyline editors provide the following API:
objectName destroy
This method destroys the polyline editor and releases all its internal resources.
Note that this operation does not destroy the items the editor managed on the
attached canvas, nor the canvas itself.
The result of the method is an empty string.
objectName enable
This method activates editing of the polyline on the canvas. This is the default
after instance creation. A call is ignored if the editor is already active.
The result of the method is an empty string.
The complementary method is disable. The interogatory method for the current state
is active.
objectName disable
This method disables editing of the polyline on the canvas. A call is ignored if
the editor is already disabled.
The result of the method is an empty string.
The complementary method is enable. The interogatory method for the current state
is active.
objectName active
This method queries the editor state.
The result of the method is a boolean value, true if the editor is active, and
false otherwise, i.e. disabled.
The methods to change the state are enable and disable.
objectName add x y
This method programmatically adds a vertex at the specified location to the line.
The result of the method is an empty string.
Note that this method goes through the whole set of callbacks invoked when the user
interactively creates a vertex, i.e. -create-cmd, and, more importantly, -data-
cmd.
One important difference however. The new vertex is always added at the end of the
line, whereas interactive creation uses heuristics to splice it into the line at a
suitable location.
This is the method through which to load the vertices of a pre-existing line into
an editor instance.
objectName clear
This method programmatically removes all vertices from the editor, essentially
removing the whole line.
The result of the method is an empty string.
Note that this method goes through the same callbacks invoked when the user
interactively removes a vertex, i.e. -data-cmd.
OPTIONS
The class command accepts the following options
-tag string
The value of this option is the name of the canvas tag with which to identify all
items of all vertices managed by the editor.
This option can only be set at construction time.
If not specified it defaults to POLYLINE
-create-cmd command-prefix
The value of this option is a command prefix the editor will invoke when it has to
create a new vertex.
This option can only be set at construction time.
If not specified it defaults to a command which will create a black-bordered blue
circle of radius 3 centered on the location of the new point.
The signature of this command prefix is
createCmd canvas x y
The result of the command prefix must be a list of the canvas items it
created to represent the marker. Note here that the visual representation of
a "vertex" may consist of multiple canvas items in an arbitrary shape.
The returned list of items is allowed to be empty, and such is taken as
signal that the callback vetoed the creation of the vertex.
-highlight-cmd command-prefix
The value of this option is a command prefix the editor will invoke when it has to
(un)highlight a vertex.
This option can only be set at construction time.
If not specified it defaults to a command which will re-color the item to highlight
in red (and restores the color for unhighlighting).
The two signatures of this command prefix are
highlightCmd on canvas item
This method of the command prefix has to perform whatever is needed to
highlight the vertex the item is a part of (remember the note above about
points allowed to be constructed from multiple canvas items).
The result of the command can be anything and will be passed as is as
argument state to the off method.
highlightCmd off canvas state
This method is invoked to unhighlight a vertex described by the state, which
is the unchanged result of the on method of the command prefix. The result
of this method is ignored.
Note any interaction between dragging and highlighting of vertices is
handled within the editor, and that the callback bears no responsibility for
doing such.
-data-cmd command-prefix
The value of this option is a command prefix the editor will invoke when the line
was edited in some way (vertex added, removed, moved). This is how the editor
delegates the actual storage of the line information to an outside object.
This option can only be set at construction time.
If not specified it defaults to an empty string and is ignored by the editor, i.e.
not invoked.
The signature of this command prefix is
dataCmd editorObj coordinates
This callback is invoked when the line was changed either interactively, or
programmatically. See instance method add for the latter.
The editorObj identifies the instance invoking the callback, whereas
coordinates is a list of vertex locations, with each location a pair of x-
and y-coordinates.
The result of this method is ignored.
KEYWORDS
canvas, editing, polyline