'\"
'\" Generated from file 'crosshair\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2003 Kevin Kenny
'\" Copyright (c) 2008 (docs) Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>
'\" Copyright (c) 2013 Frank Gover, Andreas Kupries
'\"
.TH "crosshair" n 1\&.2\&.1 tklib "Crosshairs"
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.BS
.SH NAME
crosshair \- Crosshairs for Tk canvas
.SH SYNOPSIS
package require \fBTcl  ?8\&.4?\fR
.sp
package require \fBTk  ?8\&.4?\fR
.sp
package require \fBcrosshair  ?1\&.2\&.1?\fR
.sp
\fBcrosshair::crosshair\fR \fIw\fR ?\fIarg\fR\&.\&.\&.?
.sp
\fBcrosshair::off\fR \fIw\fR
.sp
\fBcrosshair::configure\fR \fIw\fR ?\fIarg\fR\&.\&.\&.?
.sp
\fBcrosshair::track\fR \fBon\fR \fIw\fR \fIcmdprefix\fR
.sp
\fBcrosshair::track\fR \fBoff\fR \fIw\fR
.sp
\fBcrosshair::bbox_add\fR \fIw\fR \fIbbox\fR
.sp
\fBcrosshair::bbox_remove\fR \fItoken\fR
.sp
.BE
.SH DESCRIPTION
The \fBcrosshair\fR package provides commands to (de)activate and
track crosshairs on canvas widgets\&.
.SH API
The following commands are exported to the public:
.TP
\fBcrosshair::crosshair\fR \fIw\fR ?\fIarg\fR\&.\&.\&.?
This command activates the display of a pair of cross-hairs for the
canvas widget \fIw\fR\&. The cross-hairs track the pointing device\&. The
result of the command is the empty string\&.
.sp
All arguments after the widget \fIw\fR are treated as options as for a
canvas line item in \fIw\fR\&. Of particular interest are \fB-fill\fR
and \fB-dash\fR\&.
.TP
\fBcrosshair::off\fR \fIw\fR
This command removes the cross-hairs from the canvas widget \fIw\fR\&.
Nothing is done if the widget had no cross-hairs\&. The result of the
command is the empty string\&.
.TP
\fBcrosshair::configure\fR \fIw\fR ?\fIarg\fR\&.\&.\&.?
This command changes the appearance of the cross-hairs in the canvas
widget \fIw\fR\&. It is an error to call it for a canvas which has no
cross-hairs\&.
.sp
All arguments after the widget \fIw\fR are treated as options as for a
canvas line item in \fIw\fR\&. Of particular interest are \fB-fill\fR
and \fB-dash\fR\&.
.sp
The result of the command are the current configuration settings\&.
.TP
\fBcrosshair::track\fR \fBon\fR \fIw\fR \fIcmdprefix\fR
This command activates reporting of the location of the cross-hairs in
the canvas widget \fIw\fR\&. 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\&.
.sp
After the invokation of this command the specified command prefix
\fIcmdprefix\fR will be called whenever the mouse moves within the
canvas, with 7 arguments\&. These are, in order:
.RS
.IP [1]
The widget \fIw\fR
.IP [2]
The x-location of the cross-hairs, in pixels\&.
.IP [3]
The y-location of the cross-hairs, in pixels\&.
.IP [4]
The x-location of the top-left corner of the viewport, in pixels\&.
.IP [5]
The y-location of the top-left corner of the viewport, in pixels\&.
.IP [6]
The x-location of the bottom-right corner of the viewport, in pixels\&.
.IP [7]
The y-location of the bottom-right corner of the viewport, in pixels\&.
.RE
.IP
A previously existing callback for \fIw\fR will be disabled\&. I\&.e\&. per
canvas widget with cross-hairs only one callback reporting their
location is possible\&.
.TP
\fBcrosshair::track\fR \fBoff\fR \fIw\fR
This command disables the reporting of the location of the cross-hairs
in the canvas widget \fIw\fR\&. 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\&.
.TP
\fBcrosshair::bbox_add\fR \fIw\fR \fIbbox\fR
This command adds a bounding box to the crosshairs for canvas \fIw\fR\&.
The crosshairs will only be active within that area\&.
.sp
The result of the command is a token with which the bounding
box can be removed again, see \fBcrosshair::bbox_remove\fR below\&.
.sp
The bounding box \fIbbox\fR 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:
.CS

llx lly urx ury
.CE
.sp
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
\fIunion\fR of all the specified bounding boxes\&.
.TP
\fBcrosshair::bbox_remove\fR \fItoken\fR
This command removes the bounding box specified by the \fItoken\fR (a
result of \fBcrosshair::bbox_add\fR) from the crosshairs for its
canvas widget\&.
.PP
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fItklib :: crosshair\fR of the
\fITcllib SF Trackers\fR [http://sourceforge\&.net/tracker/?group_id=12883]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fIcrosshair\fR of the
\fITklib Trackers\fR [http://core\&.tcl\&.tk/tklib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.SH KEYWORDS
canvas, cross-hairs, location, tracking, viewport
.SH COPYRIGHT
.nf
Copyright (c) 2003 Kevin Kenny
Copyright (c) 2008 (docs) Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>
Copyright (c) 2013 Frank Gover, Andreas Kupries

.fi
