canvas::edit::circle - Editing a circle on a canvas
package require
Tcl 8.5
package require
Tk 8.5
package require
canvas::edit::points ?0.1?
package require
canvas::edit::circle ?0.1?
::canvas::edit circle objectName canvas
options...
objectName destroy
objectName enable
objectName disable
objectName active
objectName set minx miny maxx maxy
objectName clear
activeCmd editorObj id
createCmd canvas x y
dataCmd editorObj coordinates
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.
The circle editor internally uses an instance of package
canvas::edit::points, and inherits all the options and behaviours for
it. The color options are additionally applied to the circle element of this
editor
Beyond that it provides an option,
-circle-config, to customize the
circle item used to render the circle through its principal points. Note that
it cannot overide the inherited color options.
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.
-
::canvas::edit circle objectName
canvas options...
- This, the class command, creates and configures a new
instance of a circle editor, named objectName. The instance will be
connected to the specified canvas widget.
The result of the command is the fully qualified name of the instance
command.
The options accepted here, and their values, are explained in the section
Options.
Instances of the circle editors provide the following API:
-
objectName destroy
- This method destroys the circle editor and releases all its
internal resources.
Note that this operation does not destroy the items the editor managed on
the attached canvas, nor the canvas itself.
The result of the method is an empty string.
-
objectName enable
- 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.
The result of the method is an empty string.
The complementary method is disable. The interogatory method for the
current state is active.
-
objectName disable
- This method disables editing of the circle on the canvas. A
call is ignored if the editor is already disabled.
The result of the method is an empty string.
The complementary method is enable. The interogatory method for the
current state is active.
-
objectName active
- This method queries the editor state.
The result of the method is a boolean value, true if the editor is
active, and false otherwise, i.e. disabled.
The methods to change the state are enable and disable.
-
objectName set minx miny
maxx maxy
- This method programmatically set the circle from the border
coordinates. This writes over a previous (possibly partial) circle.
The result of the method is an empty string.
Note that this method goes through the whole set of callbacks invoked when
the principal points are created, i.e. -create-cmd, and, more
importantly, -data-cmd.
This is the method through which to load a pre-existing circle into an
editor instance.
-
objectName clear
- This method programmatically removes the circle from the
editor, making the way free for creating a new one.
The result of the method is an empty string.
Note that this method goes through the same callbacks invoked when the user
interactively removes a principal point, i.e. -data-cmd.
The class command accepts the following options
-
-active-cmd command-prefix
- 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.
If not specified it defaults to an empty command which does nothing.
The signature of this command prefix is
-
activeCmd editorObj id
-
The id identifies the entered object.
An empty id indicates that the last entered object was left.
The value circle indicates that the circle's outline was entered.
Any other value is a code for one of the circle's principal points, i.e.
center, and edge.
The result of this method is ignored.
-
-add-remove-point eventspec
- The value of this option is an event specification (without
bracketing angles) declaring which event will trigger adding and removing
a point.
This option can only be set at construction time.
The default setup uses different events for adding and removing points,
ButtonPress-1 and ButtonPress-2 respectively.
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.
-
-circle-config list
- 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 cannot override
the principal coloring of the circle as applied by the main options
-color and -hilit-color.
If not specified it defaults to the empty list.
-
-color colorspec
- The value of this option is the fill color for the default
item created when adding a point, and no -create-cmd is specified.
The default value is SkyBlue2.
-
-create-cmd command-prefix
- The value of this option is a command prefix the editor
will invoke when it has to create a new principal point.
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.
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.
The signature of this command prefix is
-
createCmd canvas x y
- The result of the command prefix must 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.
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.
-
-data-cmd command-prefix
- 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.
This option can only be set at construction time.
If not specified it defaults to an empty string and is ignored by the
editor, i.e. not invoked.
The signature of this command prefix is
-
dataCmd editorObj coordinates
- This callback is invoked when the circle was changed either
interactively, or programmatically. See instance method set for the
latter.
The editorObj identifies the instance invoking the callback, whereas
coordinates 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.
The result of this method is ignored.
-
-drag-point eventspec
- The value of this option is an event specification (without
bracketing angles) declaring which event will trigger a drag action on
points.
This option can only be set at construction time.
The default specification is ButtonPress-3.
-
-hilit-color colorspec
- The value of this option is the highlight color for the
default item created when adding a point, and no -highlight-cmd is
specified.
The default value is red.
-
-kind name
- The value of this option is the canvas item type for the
default item created when adding a point, and no -create-cmd is
specified. Only item types specified through a bounding box are suitable.
The default value is oval.
-
-radius int
- The value of this option is the radius for the default item
created when adding a point, and no -create-cmd is specified.
The default value is 3.
-
-tag string
- 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.
This option can only be set at construction time.
If not specified it defaults to CIRCLE
This document, and the package it describes, will undoubtedly contain bugs and
other problems. Please report such in the category
canvas of the
Tklib Trackers [
http://core.tcl.tk/tklib/reportlist]. Please also
report any ideas for enhancements you may have for either package and/or
documentation.
canvas, circle, editing