crosshair(n) Crosshairs crosshair(n)______________________________________________________________________________NAMEcrosshair - 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
_________________________________________________________________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 set‐
tings.
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 pre‐
fix 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 view‐
port, in pixels.
[7] The y-location of the bottom-right corner of the view‐
port, 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)
