1crosshair(n)                      Crosshairs                      crosshair(n)
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NAME

8       crosshair - Crosshairs for Tk canvas
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SYNOPSIS

11       package require Tcl  ?8.4?
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13       package require Tk  ?8.4?
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15       package require crosshair  ?1.0.2?
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17       crosshair::crosshair w ?arg...?
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19       crosshair::off w
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21       crosshair::configure w ?arg...?
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23       crosshair::track on w cmdprefix
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25       crosshair::track off w
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DESCRIPTION

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

34       The following commands are exported to the public:
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36       crosshair::crosshair w ?arg...?
37              This command activates the display of a pair of cross-hairs  for
38              the  canvas widget w. The cross-hairs track the pointing device.
39              The result of the command is the empty string.
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41              All arguments after the widget w are treated as options as for a
42              canvas  line  item  in  w.  Of particular interest are -fill and
43              -dash.
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45       crosshair::off w
46              This command removes the cross-hairs from the canvas  widget  w.
47              Nothing  is done if the widget had no cross-hairs. The result of
48              the command is the empty string.
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50       crosshair::configure w ?arg...?
51              This command changes the appearance of the  cross-hairs  in  the
52              canvas  widget  w.  It is an error to call it for a canvas which
53              has no cross-hairs.
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55              All arguments after the widget w are treated as options as for a
56              canvas  line  item  in  w.  Of particular interest are -fill and
57              -dash.
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59              The result of the command are  the  current  configuration  set‐
60              tings.
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62       crosshair::track on w cmdprefix
63              This  command  activates reporting of the location of the cross-
64              hairs in the canvas widget w. It is an error to use this command
65              for a canvas which has no cross-hairs. The result of the command
66              is the empty string.
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68              After the invokation of this command the specified command  pre‐
69              fix cmdprefix will be called whenever the mouse moves within the
70              canvas, with 7 arguments. These are, in order:
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72              [1]    The widget w
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74              [2]    The x-location of the cross-hairs, in pixels.
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76              [3]    The y-location of the cross-hairs, in pixels.
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78              [4]    The x-location of the top-left corner of the viewport, in
79                     pixels.
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81              [5]    The y-location of the top-left corner of the viewport, in
82                     pixels.
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84              [6]    The x-location of the bottom-right corner  of  the  view‐
85                     port, in pixels.
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87              [7]    The  y-location  of  the bottom-right corner of the view‐
88                     port, in pixels.
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90              A previously existing callback for w will be disabled. I.e.  per
91              canvas widget with cross-hairs only one callback reporting their
92              location is possible.
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94       crosshair::track off w
95              This command disables the  reporting  of  the  location  of  the
96              cross-hairs  in  the canvas widget w. It is an error to use this
97              command for a canvas which has no cross-hairs. The result of the
98              command is the empty string.
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BUGS, IDEAS, FEEDBACK

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

108       canvas, cross-hairs, location, tracking, viewport
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111       Copyright (c) 2003 Kevin Kenny
112       Copyright (c) 2008 (docs) Andreas Kupries <andreas_kupries@users.sourceforge.net>
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117crosshair                            1.0.2                        crosshair(n)
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