plucky (3) canvas::edit::rectangle.3tk.gz

Provided by: tklib_0.9-1_all bug

NAME

       canvas::edit::rectangle - Editing a rectangle 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::rectangle ?0.1?

       ::canvas::edit rectangle objectName canvas options...

       objectName destroy

       objectName enable

       objectName disable

       objectName active

       objectName set minx miny maxx maxy

       objectName clear

       activeCmd editorObj id

       createCmd canvas x y

       dataCmd editorObj coordinates

________________________________________________________________________________________________________________

DESCRIPTION

       This  package  provides  a class whose instances handle editing a rectangle on a canvas. Instances can be
       configured with regard to the visual appearance of the markers denoting  the  rectangle's  corners.  Note
       that instances do not store the edited rectangle themselves, but delegate this to a configurable object.

INTERACTION

       The  rectangle  editor  internally uses an instance of package canvas::edit::points, and inherits all the
       options and behaviours for it. The color options are additionally applied to  the  rectangle  element  of
       this editor

       Beyond  that  it  provides  an  option,  -rect-config, to customize the rectangle item used to render the
       rectangle through its corners. Note that it cannot overide the inherited color options.

       During interaction instances execute a state machine where the user creates two points,  at  which  point
       the  system  completes  the  rectangle  with the missing corners and reports it. At that point the system
       prevents adding more points. Dragging the points is still possible,  enabling  resizing  and  moving  the
       rectangle. Deleting any corner deletes the entire rectangle, at which point the system is again ready for
       the creation of a new rectangle from two points.

CLASS API

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

       objectName destroy
              This method destroys the rectangle 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 rectangle 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 rectangle 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 set minx miny maxx maxy
              This  method  programmatically  set the rectangle from the border coordinates.  This writes over a
              previous (possibly partial) rectangle.

              The result of the method is an empty string.

              Note that this method goes through the whole set of callbacks invoked when  corners  are  created,
              i.e.  -create-cmd, and, more importantly, -data-cmd.

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

       objectName clear
              This  method  programmatically  removes  the  rectangle  from  the editor, making the way free for
              creating a new one.

              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 corner, i.e. -data-cmd.

OPTIONS

       The class command accepts the following options

       -active-cmd command-prefix
              The  value  of  this  option  is  a command prefix the editor will invoke when the mouse enters or
              leaves the rectangle or a corner managed by the instance.

              If not specified it defaults to an empty command which does nothing.

              The signature of this command prefix is

              activeCmd editorObj id

                     The id identifies the entered object.

                     An empty id indicates that the last entered object was left.

                     The value rect indicates that the rectangle's outline was entered.

                     Any other value is a code for one of the rectangle's corner, i.e. tl, tr, bl, and br.

                     The result of this method is ignored.

       -add-remove-point eventspec
              The value of this option is an event specification (without  bracketing  angles)  declaring  which
              event will trigger adding and removing a point.

              This option can only be set at construction time.

              The  default  setup  uses  different  events  for  adding  and  removing points, ButtonPress-1 and
              ButtonPress-2 respectively.

              When using this option the same event is used for both operations.  This  is  no  problem  because
              adding is bound as canvas-global event while removal is bound to the relevant canvas items.

       -color colorspec
              The  value  of this option is the fill color for the default item created when adding a point, and
              no -create-cmd is specified.

              The default value is SkyBlue2.

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

              While  this  option can be set after construction, it is recommended to use this feature only as a
              means of inserting custom processing to be done at creation time which  remembers  and  calls  the
              previous value of the option.

              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 "corner" 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 corner.

       -data-cmd command-prefix
              The  value of this option is a command prefix the editor will invoke when the rectangle was edited
              in some way (created, modified, deleted). This is how the editor delegates the actual  storage  of
              the rectangle 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  rectangle  was  changed  either  interactively,  or
                     programmatically.  See instance method set for the latter.

                     The editorObj identifies the instance invoking the callback, whereas coordinates is a  list
                     of  4  elements,  containing  the  min  x,  and  y,  and the max x and y coordinates of the
                     rectangle, in this order.

                     The result of this method is ignored.

       -drag-point eventspec
              The value of this option is an event specification (without  bracketing  angles)  declaring  which
              event will trigger a drag action on points.

              This option can only be set at construction time.

              The default specification is ButtonPress-3.

       -hilit-color colorspec
              The  value of this option is the highlight color for the default item created when adding a point,
              and no -highlight-cmd is specified.

              The default value is red.

       -kind name
              The value of this option is the canvas item type for the default item created when adding a point,
              and no -create-cmd is specified.  Only item types specified through a bounding box are suitable.

              The default value is oval.

       -radius int
              The  value  of  this option is the radius for the default item created when adding a point, and no
              -create-cmd is specified.

              The default value is 3.

       -rect-config list
              The value of this option is a list of options and their values  to  be  applied  to  the  internal
              rectangle  item whenever it is regenerated after changes.  Note that these options cannot override
              the principal coloring of the rectangle as applied by the main options -color and -hilit-color.

              If not specified it defaults to the empty list.

       -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 RECTANGLE

BUGS, IDEAS, FEEDBACK

       This  document,  and  the package it describes, will undoubtedly contain bugs and other problems.  Please
       report such in the category canvas of the Tklib Trackers  [http://core.tcl.tk/tklib/reportlist].   Please
       also report any ideas for enhancements you may have for either package and/or documentation.

KEYWORDS

       canvas, editing, rectangle