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Document: API Specification
Overview:
This JavaScript library is divided into 8 packages. The top-level <mxClient>
class includes (or dynamically imports) everything else. The current version
is stored in <mxClient.VERSION>.
The *editor* package provides the classes required to implement a diagram
editor. The main class in this package is <mxEditor>.
The *view* and *model* packages implement the graph component, represented
by <mxGraph>. It refers to a <mxGraphModel> which contains <mxCell>s and
caches the state of the cells in a <mxGraphView>. The cells are painted
using a <mxCellRenderer> based on the appearance defined in <mxStylesheet>.
Undo history is implemented in <mxUndoManager>. To display an icon on the
graph, <mxCellOverlay> may be used. Validation rules are defined with
<mxMultiplicity>.
The *handler*, *layout* and *shape* packages contain event listeners,
layout algorithms and shapes, respectively. The graph event listeners
include <mxRubberband> for rubberband selection, <mxTooltipHandler>
for tooltips and <mxGraphHandler> for basic cell modifications.
<mxCompactTreeLayout> implements a tree layout algorithm, and the
shape package provides various shapes, which are subclasses of
<mxShape>.
The *util* package provides utility classes including <mxClipboard> for
copy-paste, <mxDatatransfer> for drag-and-drop, <mxConstants> for keys and
values of stylesheets, <mxEvent> and <mxUtils> for cross-browser
event-handling and general purpose functions, <mxResources> for
internationalization and <mxLog> for console output.
The *io* package implements a generic <mxObjectCodec> for turning
JavaScript objects into XML. The main class is <mxCodec>.
<mxCodecRegistry> is the global registry for custom codecs.
Events:
There are three different types of events, namely native DOM events,
<mxEventObjects> which are fired in an <mxEventSource>, and <mxMouseEvents>
which are fired in <mxGraph>.
Some helper methods for handling native events are provided in <mxEvent>. It
also takes care of resolving cycles between DOM nodes and JavaScript event
handlers, which can lead to memory leaks in IE6.
Most custom events in mxGraph are implemented using <mxEventSource>. Its
listeners are functions that take a sender and <mxEventObject>. Additionally,
the <mxGraph> class fires special <mxMouseEvents> which are handled using
mouse listeners, which are objects that provide a mousedown, mousemove and
mouseup method.
Events in <mxEventSource> are fired using <mxEventSource.fireEvent>.
Listeners are added and removed using <mxEventSource.addListener> and
<mxEventSource.removeListener>. <mxMouseEvents> in <mxGraph> are fired using
<mxGraph.fireMouseEvent>. Listeners are added and removed using
<mxGraph.addMouseListener> and <mxGraph.removeMouseListener>, respectively.
Key bindings:
The following key bindings are defined for mouse events in the client across
all browsers and platforms:
- Control-Drag: Duplicates (clones) selected cells
- Shift-Rightlick: Shows the context menu
- Alt-Click: Forces rubberband (aka. marquee)
- Control-Select: Toggles the selection state
- Shift-Drag: Constrains the offset to one direction
- Shift-Control-Drag: Panning (also Shift-Rightdrag)
Configuration:
The following global variables may be defined before the client is loaded to
specify its language or base path, respectively.
- mxBasePath: Specifies the path in <mxClient.basePath>.
- mxImageBasePath: Specifies the path in <mxClient.imageBasePath>.
- mxLanguage: Specifies the language for resources in <mxClient.language>.
- mxDefaultLanguage: Specifies the default language in <mxClient.defaultLanguage>.
- mxLoadResources: Specifies if any resources should be loaded. Default is true.
- mxLoadStylesheets: Specifies if any stylesheets should be loaded. Default is true.
Reserved Words:
The mx prefix is used for all classes and objects in mxGraph. The mx prefix
can be seen as the global namespace for all JavaScript code in mxGraph. The
following fieldnames should not be used in objects.
- *mxObjectId*: If the object is used with mxObjectIdentity
- *as*: If the object is a field of another object
- *id*: If the object is an idref in a codec
- *mxListenerList*: Added to DOM nodes when used with <mxEvent>
- *window._mxDynamicCode*: Temporarily used to load code in Safari and Chrome
(see <mxClient.include>).
- *_mxJavaScriptExpression*: Global variable that is temporarily used to
evaluate code in Safari, Opera, Firefox 3 and IE (see <mxUtils.eval>).
Files:
The library contains these relative filenames. All filenames are relative
to <mxClient.basePath>.
Built-in Images:
All images are loaded from the <mxClient.imageBasePath>,
which you can change to reflect your environment. The image variables can
also be changed individually.
- mxGraph.prototype.collapsedImage
- mxGraph.prototype.expandedImage
- mxGraph.prototype.warningImage
- mxWindow.prototype.closeImage
- mxWindow.prototype.minimizeImage
- mxWindow.prototype.normalizeImage
- mxWindow.prototype.maximizeImage
- mxWindow.prototype.resizeImage
- mxPopupMenu.prototype.submenuImage
- mxUtils.errorImage
- mxConstraintHandler.prototype.pointImage
The basename of the warning image (images/warning without extension) used in
<mxGraph.setCellWarning> is defined in <mxGraph.warningImage>.
Resources:
The <mxEditor> and <mxGraph> classes add the following resources to
<mxResources> at class loading time:
- resources/editor*.properties
- resources/graph*.properties
By default, the library ships with English and German resource files.
Images:
Recommendations for using images. Use GIF images (256 color palette) in HTML
elements (such as the toolbar and context menu), and PNG images (24 bit) for
all images which appear inside the graph component.
- For PNG images inside HTML elements, Internet Explorer will ignore any
transparency information.
- For GIF images inside the graph, Firefox on the Mac will display strange
colors. Furthermore, only the first image for animated GIFs is displayed
on the Mac.
For faster image rendering during application runtime, images can be
prefetched using the following code:
(code)
var image = new Image();
image.src = url_to_image;
(end)
Deployment:
The client is added to the page using the following script tag inside the
head of a document:
(code)
<script type="text/javascript" src="js/mxClient.js"></script>
(end)
The deployment version of the mxClient.js file contains all required code
in a single file. For deployment, the complete javascript/src directory is
required.
Source Code:
If you are a source code customer and you wish to develop using the
full source code, the commented source code is shipped in the
javascript/devel/source.zip file. It contains one file for each class
in mxGraph. To use the source code the source.zip file must be
uncompressed and the mxClient.js URL in the HTML page must be changed
to reference the uncompressed mxClient.js from the source.zip file.
Compression:
When using Apache2 with mod_deflate, you can use the following directive
in src/js/.htaccess to speedup the loading of the JavaScript sources:
(code)
SetOutputFilter DEFLATE
(end)
Classes:
There are two types of "classes" in mxGraph: classes and singletons (where
only one instance exists). Singletons are mapped to global objects where the
variable name equals the classname. For example mxConstants is an object with
all the constants defined as object fields. Normal classes are mapped to a
constructor function and a prototype which defines the instance fields and
methods. For example, <mxEditor> is a function and mxEditor.prototype is the
prototype for the object that the mxEditor function creates. The mx prefix is
a convention that is used for all classes in the mxGraph package to avoid
conflicts with other objects in the global namespace.
Subclassing:
For subclassing, the superclass must provide a constructor that is either
parameterless or handles an invocation with no arguments. Furthermore, the
special constructor field must be redefined after extending the prototype.
For example, the superclass of mxEditor is <mxEventSource>. This is
represented in JavaScript by first "inheriting" all fields and methods from
the superclass by assigning the prototype to an instance of the superclass,
eg. mxEditor.prototype = new mxEventSource() and redefining the constructor
field using mxEditor.prototype.constructor = mxEditor. The latter rule is
applied so that the type of an object can be retrieved via the name of it�s
constructor using mxUtils.getFunctionName(obj.constructor).
Constructor:
For subclassing in mxGraph, the same scheme should be applied. For example,
for subclassing the <mxGraph> class, first a constructor must be defined for
the new class. The constructor calls the super constructor with any arguments
that it may have using the call function on the mxGraph function object,
passing along explitely each argument:
(code)
function MyGraph(container)
{
mxGraph.call(this, container);
}
(end)
The prototype of MyGraph inherits from mxGraph as follows. As usual, the
constructor is redefined after extending the superclass:
(code)
MyGraph.prototype = new mxGraph();
MyGraph.prototype.constructor = MyGraph;
(end)
You may want to define the codec associated for the class after the above
code. This code will be executed at class loading time and makes sure the
same codec is used to encode instances of mxGraph and MyGraph.
(code)
var codec = mxCodecRegistry.getCodec(mxGraph);
codec.template = new MyGraph();
mxCodecRegistry.register(codec);
(end)
Functions:
In the prototype for MyGraph, functions of mxGraph can then be extended as
follows.
(code)
MyGraph.prototype.isCellSelectable = function(cell)
{
var selectable = mxGraph.prototype.isSelectable.apply(this, arguments);
var geo = this.model.getGeometry(cell);
return selectable && (geo == null || !geo.relative);
}
(end)
The supercall in the first line is optional. It is done using the apply
function on the isSelectable function object of the mxGraph prototype, using
the special this and arguments variables as parameters. Calls to the
superclass function are only possible if the function is not replaced in the
superclass as follows, which is another way of �subclassing� in JavaScript.
(code)
mxGraph.prototype.isCellSelectable = function(cell)
{
var geo = this.model.getGeometry(cell);
return selectable &&
(geo == null ||
!geo.relative);
}
(end)
The above scheme is useful if a function definition needs to be replaced
completely.
In referenceId to add new functions and fields to the subclass, the following code
is used. The example below adds a new function to return the XML
representation of the graph model:
(code)
MyGraph.prototype.getXml = function()
{
var enc = new mxCodec();
return enc.encode(this.getModel());
}
(end)
Variables:
Likewise, a new field is declared and defined as follows.
(code)
MyGraph.prototype.myField = 'Hello, World!';
(end)
Note that the value assigned to myField is created only once, that is, all
instances of MyGraph share the same value. If you require instance-specific
values, then the field must be defined in the constructor instead.
(code)
function MyGraph(container)
{
mxGraph.call(this, container);
this.myField = new Array();
}
(end)
Finally, a new instance of MyGraph is created using the following code, where
container is a DOM node that acts as a container for the graph view:
(code)
var graph = new MyGraph(container);
(end)