DOKK / manpages / debian 10 / tklib / crosshair.3tk.en
crosshair(3tk) Crosshairs crosshair(3tk) 







crosshair - Crosshairs for Tk canvas








package require Tcl ?8.4?


package require Tk ?8.4?


package require crosshair ?1.1?


crosshair::crosshair w ?arg...?


crosshair::off w


crosshair::configure w ?arg...?


crosshair::track on w cmdprefix


crosshair::track off w


crosshair::bbox_add w bbox


crosshair::bbox_remove token












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








The following commands are exported to the public:



  

  
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.

  

  

  
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.

  

  
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.

  

  

  
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.





  

  
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.

  

  
This command adds a bounding box to the crosshairs for canvas w.
      The crosshairs will only be active within that area.
    
The result of the command is a token with which the bounding
        box can be removed again, see crosshair::bbox_remove below.

    
The bounding box bbox is specified thorugh a list of 4
        values, the lower left and upper right corners of the box. The order of
        values in the list is:

  






llx lly urx ury




Note that this command can be used multiple times, each call
    adding one more bounding box. In such a case the visible area is the
    union of all the specified bounding boxes.



  

  
This command removes the bounding box specified by the token (a
      result of crosshair::bbox_add) from the crosshairs for its canvas
      widget.








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.






BUGS, IDEAS, FEEDBACK


This document, and the package it describes, will undoubtedly
    contain bugs and other problems. Please report such in the category
    crosshair 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, cross-hairs, location, tracking, viewport








Copyright (c) 2003 Kevin Kenny
Copyright (c) 2008 (docs) Andreas Kupries <andreas_kupries@users.sourceforge.net>
Copyright (c) 2013 Frank Gover, Andreas Kupries








  

    1.1
    crosshair