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crosshair(n)                                     Crosshairs                                     crosshair(n)



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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

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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 com-mand command
              mand 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://source -
       forge.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>




crosshair                                           1.0.2                                       crosshair(n)