crosshair(3tk) 1.0.2 crosshair "Crosshairs"

NAME

crosshair - Crosshairs for Tk canvas

    TABLE OF CONTENTS
    SYNOPSIS
    DESCRIPTION
    API
    BUGS, IDEAS, FEEDBACK
    KEYWORDS
    COPYRIGHT

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 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 canvas, with 7 arguments. These are, in order:

The widget w
The x-location of the cross-hairs, in pixels.
The y-location of the cross-hairs, in pixels.
The x-location of the top-left corner of the viewport, in pixels.
The y-location of the top-left corner of the viewport, in pixels.
The x-location of the bottom-right corner of the viewport, in pixels.
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. Please also report any ideas for enhancements you may have for either package and/or documentation.

KEYWORDS

canvas, cross-hairs, location, tracking, viewport