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crosshair(3tk) Crosshairs crosshair(3tk) 


NAME

crosshair - Crosshairs for Tk canvas

SYNOPSIS

package require Tcl ?8.4?

 

package require Tk ?8.4?

 

package require crosshair ?1.0.2?

 

crosshair::crosshair w ?arg...?

 

crosshair::off w

 

crosshair::configure w ?arg...?

 

crosshair::track on w cmdprefix

 

crosshair::track off w

 




 


DESCRIPTION

The crosshair package provides commands to (de)activate and track
  crosshairs on canvas widgets.

API

The following commands are exported to the public:


  
crosshair::crosshair w ?arg...?

  
This command activates the display of a pair of cross-hairs
      for the canvas widget w. The cross-hairs track the pointing device.
      The result of the command is the empty string.
    
 

    All arguments after the widget w are treated as options as for a
      canvas line item in w. Of particular interest are -fill and
      -dash.





  
crosshair::off w

  
This command removes the cross-hairs from the canvas widget
      w. Nothing is done if the widget had no cross-hairs. The result of
      the command is the empty string.





  
crosshair::configure w ?arg...?

  
This command changes the appearance of the cross-hairs in
      the canvas widget w. It is an error to call it for a canvas which
      has no cross-hairs.
    
 

    All arguments after the widget w are treated as options as for a
      canvas line item in w. Of particular interest are -fill and
      -dash.
    
 

    The result of the command are the current configuration settings.





  
crosshair::track on w
    cmdprefix

  
This command activates reporting of the location of the
      cross-hairs in the canvas widget w. It is an error to use this
      command for a canvas which has no cross-hairs. The result of the command
      is the empty string.
    
 

    After the invokation of this command the specified command prefix
      cmdprefix will be called whenever the mouse moves within the
      canvas, with 7 arguments. These are, in order:







  
[1]

  
The widget w





  
[2]

  
The x-location of the cross-hairs, in pixels.





  
[3]

  
The y-location of the cross-hairs, in pixels.





  
[4]

  
The x-location of the top-left corner of the viewport, in
      pixels.





  
[5]

  
The y-location of the top-left corner of the viewport, in
      pixels.





  
[6]

  
The x-location of the bottom-right corner of the viewport,
      in pixels.





  
[7]

  
The y-location of the bottom-right corner of the viewport,
      in pixels.







  

  
A previously existing callback for w will be
      disabled. I.e. per canvas widget with cross-hairs only one callback
      reporting their location is possible.





  
crosshair::track off w

  
This command disables the reporting of the location of the
      cross-hairs in the canvas widget w. It is an error to use this
      command for a canvas which has no cross-hairs. The result of the command
      is the empty string.




BUGS, IDEAS, FEEDBACK

This document, and the package it describes, will undoubtedly contain bugs and
  other problems. Please report such in the category tklib :: crosshair
  of the Tcllib SF Trackers
  [http://sourceforge.net/tracker/?group_id=12883]. Please also report any ideas
  for enhancements you may have for either package and/or documentation.

KEYWORDS

canvas, cross-hairs, location, tracking, viewport

COPYRIGHT


Copyright (c) 2003 Kevin Kenny
Copyright (c) 2008 (docs) Andreas Kupries <andreas_kupries@users.sourceforge.net>








  

    1.0.2
    crosshair