Provided by: tklib_0.6-2_all bug

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

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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