Graph Editor

This is a graph editor widget implemented in PLT-Scheme.

For the use of this widget see the MrEd Designer.
Some ideas for the implementation of the graph editor are taken from OpenDX.
The graph editor is licensed under GPL v2.
This page contains the documentation of the graph editor.
Download the source code

Example screenshot and example code

Documentation of the objects

graph-editor%

This is the main object containing the full graph.

(new graph-editor% (callback _) (font _))

This object is derived from a canvas% object.

font controls the size of the text in the graph window and
callback is the function which is called whenever something happens in the graph window.

Public methods:

get-selected : This function returns the node that is selected in the graphical window.
layout : This function lays out graph in the area. The function ensures that no two nodes are overlapping. It is achieved in such a way that if a node would overlap another one than the other node is moved to right of the first node. This is done recursively, thus by placing the other node to the right of the first node would overlap another node then the new node is moved to the right, and so on.
clear : This function clears the graph, it deletes all nodes and lines.
node-add : This function can be used to add a node. Furthermore the function calls the callback function before and after adding the node. If the callback function returns a false value when it is called before adding the node then the node is not added!
node-del : This function can be used to delete a node, if no lines are connected. Furthermore the function calls the callback function before and after the node deletion. If the callback function returns a false value when it is called before the node deletion then the node is not deleted!
node-del! : The function deletes the node and all connecting lines without any consideration for other datastructures. This function does not call the callback function.
node-get-by-name : This function returns the node which has the given name.
node-for-each : This function calls a function for each exisint node in the graph.
line-add : This function adds a line between two node in the graph.

Overwritten events:

on-scroll
on-size
on-paint
on-subwindow-char
on-event

Callback function:
The callback function has two arguments. The first argument is a symbol denoting the action that happened in the graph window and the second argument is some data, a symbol, a list or an object depending on the action.

Action	Data	Description
select	node% object	called when the user clicks on a node
deselect	node% object	called when the node is deselected
before-line-add	(src dst)	ccalled before a line is added between the source and the destination, if the return value of the callback function is false the line is not allowed and not added
after-line-add	line% object	called after the line is added
before-line-del	(src dst)	called before a line is deleted between the source and the destination, if the return value of the callback function is false the line is not deleted
after-line-del	#f	called after the line is deleted
before-node-add	string	called before a node is added, if the return value of the callback function is false the node cannot be added
after-node-add	node% object	called after the node is added
before-node-del	node% object	called before the node is deleted, if the return value of the callback function is false the node is not deleted
after-node-del	id	called after the node has been deleted, the deleted node had the id
before-clear	#f	called before the full network is deleted, if the callback function returns #f then nothing happens
after-clear	#f	called after the network is initialised

node%

This object represents a node in the graph.

(new node% (id _) (name _) (x _) (y _) (editor _) (style _))

This object is derived from object%. It can store some user specified data as well. The node does not know anything about this data, the user must handle it!

id: the id number in the graph window
name: a string the node will display in the graph window
x: the x coordinate of the center of the node
y: the y coordinate of the center of the node
editor: it stores a "reference" to the graph editor
style: it determines the style of node. Possible values '(no-output no-input)

Public methods:

get-data: returns the user data that is stored in this node
set-data: stores the user data in this node
get-id: returns the id number of this node
get-name: returns the name of this node
set-name: stores a new name in this node. The function changes the representation of the node so if necessary it also calls the function to make a new layout of the graph
get-x: returns the x coordinate of this node
get-y: returns the y coordinate of this node
get-style: returns the style of this node
is-shown?: determines whether the node is displayed in the graph editor or not
x-set!: changes the x coordinate of this node
y-set!: changes the y coordinate of this node
get-position: returns the position of this node
get-size: returns the width and the height of this node
tab-in-count: returns the number of input tabs of this node
tab-out-count: returns the number of output tabs of this node
tab-in-ref: returns the nth input tab of this node
tab-out-ref: returns the nth output tab of this node
tab-in-connected?: determines whether any of the input tabs of this node is connected or not
tab-out-connected?: determines whether any of the output tabs of this node is connected or not
tab-in-decr: removes the most right input tab, if it is not connected to any other node
tab-out-decr: removes the most right output tab, if it is not connected to any other node<
tab-in-incr: adds a new input tab to the right of already existing input tabs
tab-out-incr: adds a new output tab to the right of already existing output tabs
show: displays this node in the graph editor
hide: hides this node in the graph editor
on-mouse: a function to call when a mouse event occured in the graph editor

tab%

This object represents an input or output tab of a node.

(new tab% (type _) (x _) (y _) (node _) (editor _))

This object is derived from object%. The lines in the graph will be connected to this object

type: the type of the tab, can be in or out
x: the x coordinate of the center of the tab
y: the y coordinate of the tab, this is not the center of the tab, but the top or the bottom of the node
node: it stores a "reference" to the node to which this tab belongs to
editor: it stores a "reference" to the graph editor

Public methods:

line-add: adds a connecting line to the tab
line-del: deletes a connecting line from the tab
get-lines: returns the list of connecting lines in the tab
connected?: determines whether there are connecting lines to the tab
get-type: returns the type of this tab
get-node: returns the node to which this tabs belongs to
x-set!: changes the x coordinate of this tab
y-set!: changes the y coordinate of this tab
get-position: returns the position of this tab
get-line-position: returns the position to which the line can be connected
show: displays this tab in the graph editor
hide: hides this tab in the graph editor
on-mouse: a function to call when a mouse event occured in the graph editor

line%

This object represents a line between two nodes.

(new line% (source _) (target _) (editor _))

This object is derived from object%.

source: this stores a "reference" to the source tab% object
target: this stores a "reference" to the destination tab% object
editor: it stores a "reference" to the graph editor

Public methods:

get-data: returns the user data that is stored in this line
set-data: stores the user data in this line
is-shown?: returns #t if the line is visible, otherwise #f
get-source: returns the source tab object of this line
get-target: returns the target tab object of this line
show: displays this tab in the graph editor
hide: hides this tab in the graph editor

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