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canvas::edit::polyline(3tk) Variations on a canvas canvas::edit::polyline(3tk) 





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 ?0.2?


::canvas::edit polyline objectName
    canvas options...


objectName destroy


objectName enable


objectName disable


objectName active


objectName add x y


objectName clear


activeCmd editorObj id


createCmd canvas x y


dataCmd editorObj coordinates










DESCRIPTION


This package provides a class whose instances handle editing a
    single poly-line (or -gon) on a canvas. Instances can be configured with
    regard to the visual appearance of the markers denoting the line's vertices,
    as well as if the line is to be closed or not, and further if a closed line
    has to be convex or not. Note that instances do not store the edited
    polyline themselves, but delegate this to a configurable object.






INTERACTION


The polyline 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 line element of this
    editor


Beyond that it provides 2 options to configure the editing mode,
    and one option to customize the line/polygon item used to render the line
    through the points.


The main editing mode is controlled by option -closed for
    line (i.e. open) versus polygon (i.e. closed). The default is
    line/open mode.


In polygon/closed mode the option -convex controls if the
    editor enforces convexity of the polygon, or not. The default is no
    enforcement of convexity.


The option -line-config enables basic customization of the
    line/polygon item. Note that it cannot overide the inherited color
  options.






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:



  

  
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.

  








OPTIONS


The class command accepts the following options



  

  
The value of this option is a command prefix the editor will invoke when
      the mouse enters or leaves the line or a point managed by the instance.
    
If not specified it defaults to an empty command which does
        nothing.

    
The signature of this command prefix is

  







  

  

    
The id identifies the entered object.

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

    
The value line indicates that the line was entered.

    
A numeric value N indicates that the N'th vertex
        of the line was entered, counting from 0.

    
The result of this method is ignored.

  







  

  
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.

  

  

  
The value of this option is a boolean flag indicating if the edited
      polyline is closed, i.e. a loop, or not. NOTE that a proper loop
      requires at least 3 points. For less than that an open line is shown, or
      even just a point.
    
This option can only be set at construction time.

    
If not specified it defaults to false

  

  

  
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.

  

  

  
The value of this option is a boolean flag indicating if the edited
      polyline is strictly convex, or not. This option has meaning if and only
      if option -closed is configured to be true.
    
This option can only be set at construction time.

    
If not specified it defaults to false

  

  

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

  







  

  
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
      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.

  







  

  
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.

  

  

  
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.

  

  

  
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.

  

  

  
The value of this option is a list of options and their values to be
      applied to the internal line/polygon item whenever it is regenerated after
      changes. Note that these options cannot override the principal
      coloring of the line/polygon as applied by the main options -color
      and -hilit-color.
    
If not specified it defaults to the empty list.

  

  

  
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.

  

  

  
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

  








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, polyline







  

    0.2
    tklib