'\"
'\" Generated from file 'canvas_ecircle\&.man' by tcllib/doctools with format 'nroff'
'\"
.TH "canvas::edit::circle" n 0\&.1 tklib "Variations on a canvas"
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.SH "STANDARD OPTIONS"
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.BS
.SH NAME
canvas::edit::circle \- Editing a circle on a canvas
.SH SYNOPSIS
package require \fBTcl 8\&.5\fR
.sp
package require \fBTk 8\&.5\fR
.sp
package require \fBcanvas::edit::points ?0\&.1?\fR
.sp
package require \fBcanvas::edit::circle ?0\&.1?\fR
.sp
\fB::canvas::edit\fR \fBcircle\fR \fIobjectName\fR \fIcanvas\fR \fIoptions\fR\&.\&.\&.
.sp
\fBobjectName\fR \fBdestroy\fR
.sp
\fBobjectName\fR \fBenable\fR
.sp
\fBobjectName\fR \fBdisable\fR
.sp
\fBobjectName\fR \fBactive\fR
.sp
\fBobjectName\fR \fBset\fR \fIminx\fR \fIminy\fR \fImaxx\fR \fImaxy\fR
.sp
\fBobjectName\fR \fBclear\fR
.sp
\fBactiveCmd\fR \fIeditorObj\fR \fIid\fR
.sp
\fBcreateCmd\fR \fIcanvas\fR \fIx\fR \fIy\fR
.sp
\fBdataCmd\fR \fIeditorObj\fR \fIcoordinates\fR
.sp
.BE
.SH DESCRIPTION
This package provides a class whose instances handle editing a circle on a canvas\&. Instances can be
configured with regard to the visual appearance of the markers denoting the circle's principal
points\&. Note that instances do not store the edited circle themselves, but delegate this to a
configurable object\&.
.SH INTERACTION
.PP
The circle editor internally uses an instance of package \fBcanvas::edit::points\fR,
and inherits all the options and behaviours for it\&. The color options are additionally applied to
the circle element of this editor
.PP
Beyond that it provides an option, \fB-circle-config\fR, to customize the circle item used
to render the circle through its principal points\&. Note that it cannot overide the inherited color
options\&.
.PP
During interaction instances execute a state machine where the user creates two points, at
which point the system completes the circle and reports it\&. At that point the system prevents adding
more points\&. Dragging the points is still possible, enabling resizing and moving the
circle\&. Deleting any of the principal points deletes the entire circle, at which point the system is
again ready for the creation of a new circle from two points\&.
.SH "CLASS API"
.TP
\fB::canvas::edit\fR \fBcircle\fR \fIobjectName\fR \fIcanvas\fR \fIoptions\fR\&.\&.\&.
This, the class command, creates and configures a new instance of a
circle editor, named \fIobjectName\fR\&. The instance will be
connected to the specified \fIcanvas\fR widget\&.
.sp
The result of the command is the fully qualified name of the
instance command\&.
.sp
The options accepted here, and their values, are explained in
the section \fBOptions\fR\&.
.PP
.SH "INSTANCE API"
Instances of the circle editors provide the following API:
.TP
\fBobjectName\fR \fBdestroy\fR
This method destroys the circle editor and releases all its
internal resources\&.
.sp
Note that this operation does not destroy the items the editor
managed on the attached canvas, nor the canvas itself\&.
.sp
The result of the method is an empty string\&.
.TP
\fBobjectName\fR \fBenable\fR
This method activates editing of the circle on the canvas\&. This
is the default after instance creation\&. A call is ignored if the
editor is already active\&.
.sp
The result of the method is an empty string\&.
.sp
The complementary method is \fBdisable\fR\&. The interogatory
method for the current state is \fBactive\fR\&.
.TP
\fBobjectName\fR \fBdisable\fR
This method disables editing of the circle on the canvas\&. A call
is ignored if the editor is already disabled\&.
.sp
The result of the method is an empty string\&.
.sp
The complementary method is \fBenable\fR\&. The interogatory
method for the current state is \fBactive\fR\&.
.TP
\fBobjectName\fR \fBactive\fR
This method queries the editor state\&.
.sp
The result of the method is a boolean value, \fBtrue\fR if
the editor is active, and \fBfalse\fR otherwise, i\&.e\&. disabled\&.
.sp
The methods to change the state are \fBenable\fR and
\fBdisable\fR\&.
.TP
\fBobjectName\fR \fBset\fR \fIminx\fR \fIminy\fR \fImaxx\fR \fImaxy\fR
This method programmatically set the circle from the border coordinates\&.
This writes over a previous (possibly partial) circle\&.
.sp
The result of the method is an empty string\&.
.sp
Note that this method goes through the whole set of callbacks invoked when the principal
points are created, i\&.e\&. \fB-create-cmd\fR, and, more importantly, \fB-data-cmd\fR\&.
.sp
This is the method through which to load a pre-existing circle into an editor instance\&.
.TP
\fBobjectName\fR \fBclear\fR
This method programmatically removes the circle from the editor, making the way free for creating
a new one\&.
.sp
The result of the method is an empty string\&.
.sp
Note that this method goes through the same callbacks invoked when the user interactively
removes a principal point, i\&.e\&. \fB-data-cmd\fR\&.
.PP
.SH OPTIONS
The class command accepts the following options
.TP
\fB-active-cmd\fR \fIcommand-prefix\fR
The value of this option is a command prefix the editor will invoke when the mouse enters or leaves
the circle or one of the principal points managed by the instance\&.
.sp
If not specified it defaults to an empty command which does nothing\&.
.sp
The signature of this command prefix is
.RS
.TP
\fBactiveCmd\fR \fIeditorObj\fR \fIid\fR
.sp
The \fIid\fR identifies the entered object\&.
.sp
An empty \fIid\fR indicates that the last entered object was left\&.
.sp
The value \fBcircle\fR indicates that the circle's outline was entered\&.
.sp
Any other value is a code for one of the circle's principal points, i\&.e\&. \fBcenter\fR, and
\fBedge\fR\&.
.sp
The result of this method is ignored\&.
.RE
.TP
\fB-add-remove-point\fR \fIeventspec\fR
The value of this option is an event specification (without bracketing angles) declaring which event
will trigger adding and removing a point\&.
.sp
This option can only be set at construction time\&.
.sp
The default setup uses different events for adding and removing points, \fBButtonPress-1\fR
and \fBButtonPress-2\fR respectively\&.
.sp
When using this option the same event is used for both operations\&. This is no problem because
adding is bound as canvas-global event while removal is bound to the relevant canvas items\&.
.TP
\fB-circle-config\fR \fIlist\fR
The value of this option is a list of options and their values to be applied to the internal circle
item whenever it is regenerated after changes\&.
Note that these options \fIcannot\fR override the principal coloring of the circle as applied by
the main options \fB-color\fR and \fB-hilit-color\fR\&.
.sp
If not specified it defaults to the empty list\&.
.TP
\fB-color\fR \fIcolorspec\fR
The value of this option is the fill color for the default item created when adding a point, and no
\fB-create-cmd\fR is specified\&.
.sp
The default value is \fBSkyBlue2\fR\&.
.TP
\fB-create-cmd\fR \fIcommand-prefix\fR
The value of this option is a command prefix the editor will invoke when it has to create a new
principal point\&.
.sp
While this option can be set after construction, it is recommended to use this feature only
as a means of inserting custom processing to be done at creation time which remembers and calls the
previous value of the option\&.
.sp
If not specified it defaults to a command which will create a
black-bordered blue circle of radius 3 centered on the location of the
new point\&.
.sp
The signature of this command prefix is
.RS
.TP
\fBcreateCmd\fR \fIcanvas\fR \fIx\fR \fIy\fR
The result of the command prefix \fImust\fR be a list of the canvas items it created to represent
the marker\&. Note here that the visual representation of a "principal point" may consist of multiple
canvas items in an arbitrary shape\&.
.sp
The returned list of items is allowed to be empty, and such is taken as signal that the
callback vetoed the creation of the principal point\&.
.RE
.TP
\fB-data-cmd\fR \fIcommand-prefix\fR
The value of this option is a command prefix the editor will invoke when the circle was edited in
some way (created, modified, deleted)\&. This is how the editor delegates the actual storage of the
circle information to an outside object\&.
.sp
This option can only be set at construction time\&.
.sp
If not specified it defaults to an empty string and is ignored
by the editor, i\&.e\&. not invoked\&.
.sp
The signature of this command prefix is
.RS
.TP
\fBdataCmd\fR \fIeditorObj\fR \fIcoordinates\fR
This callback is invoked when the circle was changed either interactively, or programmatically\&.
See instance method \fBset\fR for the latter\&.
.sp
The \fIeditorObj\fR identifies the instance invoking the callback, whereas \fIcoordinates\fR
is a list of 4 elements, containing the min x, and y, and the max x and y coordinates of the
circle, in this order\&.
.sp
The result of this method is ignored\&.
.RE
.TP
\fB-drag-point\fR \fIeventspec\fR
The value of this option is an event specification (without bracketing angles) declaring which event
will trigger a drag action on points\&.
.sp
This option can only be set at construction time\&.
.sp
The default specification is \fBButtonPress-3\fR\&.
.TP
\fB-hilit-color\fR \fIcolorspec\fR
The value of this option is the highlight color for the default item created when adding a point,
and no \fB-highlight-cmd\fR is specified\&.
.sp
The default value is \fBred\fR\&.
.TP
\fB-kind\fR \fIname\fR
The value of this option is the canvas item type for the default item created when adding a point,
and no \fB-create-cmd\fR is specified\&.
Only item types specified through a bounding box are suitable\&.
.sp
The default value is \fBoval\fR\&.
.TP
\fB-radius\fR \fIint\fR
The value of this option is the radius for the default item created when adding a point,
and no \fB-create-cmd\fR is specified\&.
.sp
The default value is \fB3\fR\&.
.TP
\fB-tag\fR \fIstring\fR
The value of this option is the name of the canvas tag with which to
identify all items of all vertices managed by the editor\&.
.sp
This option can only be set at construction time\&.
.sp
If not specified it defaults to \fBCIRCLE\fR
.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 \fIcanvas\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, circle, editing
