Provided by: tklib_0.6-3_all bug

NAME

       canvas::edit::points - Editing a cloud of points on a canvas

SYNOPSIS

       package require Tcl  8.5

       package require Tk  8.5

       package require canvas::edit::points  ?0.1?

       ::canvas::edit points 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 add editorObj id x y

       dataCmd remove editorObj id

       dataCmd move start editorObj id

       dataCmd move delta editorObj id x y dx dy

       dataCmd move done editorObj id

_________________________________________________________________

DESCRIPTION

       This package provides a class whose instances handle editing a cloud of point markers on a
       canvas. Instances can be configured with  regard  to  the  visual  appearance  of  markers
       (regular, and highlighted). Note that instances do not store the edited points themselves,
       but delegate this to a configurable object.

CLASS API

       ::canvas::edit points objectName canvas options...
              This, the class command, creates and configures a new instance  of  a  point  cloud
              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 point cloud editors provide the following API:

       objectName destroy
              This method  destroys  the  point  cloud  editor  and  releases  all  its  internal
              resources.

              Note that this operation does not destroy the items of the point markers 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 point cloud 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 point cloud 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 creates a point at the specified location.

              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 point, i.e.  -create-cmd, and, more importantly, -data-cmd.

              This is the method through  which  to  load  pre-existing  points  into  an  editor
              instance.

       objectName clear
              This method programmatically removes all points from the editor.

              The result of the method is an empty string.

              Note  that  this  method  goes  through  the  same  callback  invoked when the user
              interactively removes a point, 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 points managed by the editor.

              This option can only be set at construction time.

              If not specified it defaults to POINT

       -create-cmd command-prefix
              The  value of this option is a command prefix the editor will invoke when it has to
              create a new point.

              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 "point" 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 point.

       -highlight-cmd command-prefix
              The value of this option is a command prefix the editor will invoke when it has  to
              (un)highlight a point.

              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  point  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 point 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 points 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 a point
              was edited in some way. This is how the editor  delegates  the  actual  storage  of
              point 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 signatures of this command prefix are

              dataCmd add editorObj id x y
                     This callback is invoked when a new point was added to the instance,  either
                     interactively, or programmatically.  See instance method add for the latter.

                     The  id  identifies  the point within the editor and will be used by the two
                     other callbacks to specify which point to modify.

                     The last two arguments x and y specify the location  of  the  new  point  in
                     canvas coordinates.

                     The result of this method is ignored.

              dataCmd remove editorObj id
                     This callback is invoked when a point removed from the editor instance.

                     The id identifies the removed point within the editor.

                     The result of this method is ignored.

              dataCmd move start editorObj id
                     This callback is invoked when the movement of a point in the editor instance
                     has started.

                     The id identifies the point within the editor about to be moved.

                     The result of this method is ignored.

              dataCmd move delta editorObj id x y dx dy
                     This callback is invoked when the point moved in the editor instance.

                     The id identifies the moved point  within  the  editor,  and  the  remaining
                     arguments  x,  y, dx, and dy provide the new absolute location of the point,
                     and full delta to the original location.

                     At the time of the calls the system is not committed to the move  yet.  Only
                     after  method  move  done  was invoked and has accepted or rejected the last
                     position will  the  editor  update  its  internal  data  structures,  either
                     committing  to  the  new  location, or rolling the move back to the original
                     one.

                     Given this the location data provided here should be saved only in temporary
                     storage until then.

                     The result of this method is ignored.

              dataCmd move done editorObj id
                     This callback is invoked when the movement of a point in the editor instance
                     is complete.

                     The id identifies the moved point within the editor.

                     The result of this method must be a boolean value.  If  the  method  returns
                     false the move is vetoed and rollbed back.

KEYWORDS

       canvas, editing, point cloud, points