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 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 can-
	      vas, 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>

crosshair							       1.0.2							      crosshair(n)