DOKK / manpages / debian 10 / tklib / canvas::edit::points.3tk.en
canvas::edit::points(3tk) Variations on a canvas canvas::edit::points(3tk) 







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








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












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.









  
::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.

  










Instances of the point cloud editors provide the following
  API:



  

  
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.

  

  

  
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.

  

  

  
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.

  

  

  
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.

  

  

  
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.

  

  

  
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.

  










The class command accepts the following options



  

  
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

  

  

  
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

  







  

  
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.

  







  

  
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

  







  

  

    
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.

  

  

  

    
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.

  







  

  
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

  







  

  
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.

  

  

  
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.

  

  

  
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.

  

  

  
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.

  

  

  
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.

  












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.








canvas, editing, point cloud, points







  

    0.1
    canvas