Provided by: tklib_0.6-3_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