DOKK / manpages / debian 11 / tklib / canvas::edit::polyline.3tk.en
canvas::edit::polyline(3tk) Variations on a canvas canvas::edit::polyline(3tk) 







canvas::edit::polyline - Editing a polyline on a canvas








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












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.









  
::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.

  










Instances of the polyline editors provide the following API:



  

  
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.

  

  

  
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.

  

  

  
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.

  

  

  
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 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.

  

  

  
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.

  










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 vertices managed by the editor.
    
This option can only be set at construction time.

    
If not specified it defaults to POLYLINE

  

  

  
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

  







  

  
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.

  







  

  
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

  







  

  

    
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.

  

  

  

    
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.

  







  

  
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

  







  

  
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.

  












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, polyline







  

    0.1
    tklib