canvas::edit::polyline - Editing a polyline on a canvas
This package provides a class whose instances handle editing a single poly-line (or -gon) on a canvas. Instances can be configured with regard to the visual appearance of the markers denoting the line's vertices, as well as if the line is to be closed or not, and further if a closed line has to be convex or not. Note that instances do not store the edited polyline themselves, but delegate this to a configurable object.
The polyline 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 line element of this editor
Beyond that it provides 2 options to configure the editing mode, and one option to customize the line/polygon item used to render the line through the points.
The main editing mode is controlled by option -closed for line (i.e. open) versus polygon (i.e. closed). The default is line/open mode.
In polygon/closed mode the option -convex controls if the editor enforces convexity of the polygon, or not. The default is no enforcement of convexity.
The option -line-config enables basic customization of the line/polygon item. Note that it cannot overide the inherited color options.
This, the class command, creates and configures a new instance of a polyline 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 polyline editors provide the following API:
This method destroys the polyline 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.
This method activates editing of the polyline 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.
This method disables editing of the polyline 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.
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.
This method programmatically adds a vertex at the specified location to the line.
The result of the method is an empty string.
Note that this method goes through the whole set of callbacks invoked when the user interactively creates a vertex, i.e. -create-cmd, and, more importantly, -data-cmd.
One important difference however. The new vertex is always added at the end of the line, whereas interactive creation uses heuristics to splice it into the line at a suitable location.
This is the method through which to load the vertices of a pre-existing line into an editor instance.
This method programmatically removes all vertices from the editor, essentially removing the whole line.
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 vertex, i.e. -data-cmd.
The class command accepts the following options
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. Please also report any ideas for enhancements you may have for either package and/or documentation.