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The Geomajas graphics Project is a stand-alone project under the Geomajas banner.
The Geomajas Graphics project will provide drawing capabilities (SVG, VML) in support of advanced client side redlining, annotation or mark-ups. Basic use cases are dragging resizing, labeling, styling and CRUD. The idea is to create a graphics library that does not necessarily depend on the Geomajas client, but draws directly into SVG or VML. By doing so we could create a general purpose graphics library that might be useful outside Geomajas or even the GIS world as well. The project is will therefore not depend on any a priori geographical constructs like coordinate spaces or transformations. In Geomajas speak, the project focusses on annotating objects in screen space, not in world space (although the latter will emerge from world referencing the screen objects, but this is considered a separate stage).
The idea is to support different types of annotations and interaction mechanisms, some of which are:
graphical objects of varying nature, primarily based on what is available in SVG: points/markers, rectangles, ellipses, paths, lines, polygons, images, text
object attributes like color, font, line style, opacity
associations of text with objects, also known as labeling
specific objects like notes, callouts, popups
basic operations like adding, deleting, dragging, resizing, moving back/front
advanced operations like styling, coordinate-by-coordinate editing, uploading images, grouping
The goal is to achieve the equivalent of typical drawing applications like PowerPoint or OpenOffice Draw, etc... but with a focus on annotating other objects (think geographical features or imagery).
The project will of course smoothly integrate with the Geomajas Client and, in combination with the Geometry Editing plug-in, you should be able to reuse the intuïtive, yet powerful ways of changing the Path (add/remove intermediate points, etc.). The following picture illustrates the relationship of the Graphics project with other projects:
The project depends on the GWT Graphics project for rendering and the Geometry project for simple geometry concepts and geometrical calculations. The Geomajas Editing plugin will be extended with an extra module that hooks up the geometry editor to the graphical object controller framework (see architecture), making sure that the Graphics project itself stays light-weight and independent of the more complex editing mechanisms defined by the Editing plugin.
The initial version of the project will support the following object types:
Ellipse (including circles)
The following operations will be available:
Initial object creation
Moving objects back and front
Object persistence: preferably standards, through SVG
GraphicsObject is an object that can be rendered in a
GraphicsObjectContainer. The container supports
addition/removal and update of objects and sends out events on the
EventBus for each of these operations. The
GraphicsObjectContainer wraps the "physical"
VectorObjectContainer that implements the rendering of the
objects in SVG or VML.
GraphicsObject supports different types of roles,
depending on the context and the operation that the object is subjected
to. The following roles can be distinguished:
Labeled and so on. Possible
GImage, etc...Graphics objects usually do not directly
implement these roles but use role-composition instead, making them
dynamically extensible. Graphics objects can be rendered by supporting the
GraphicsObjectController is responsible for
interpreting user events and converting them into operations that will
eventually be applied to the graphics objects by the
GraphicsService (see further). The controller has access to
VectorObjectContainer to render helper objects like
handlers (for resizing), drag lines (while creating a path) or drag masks
(while dragging) and can register for whatever mouse events or key events
it is interested in. Possible
PropertyEditController, etc...Controllers act on one object
only (controller-per-instance or a single controller for all instances
with varying object scope) and can be activated and deactivated.
Activation can be achieved by defining a special meta-controller
that activates the controller(s) for a specific object. Initially a
single-selection meta-controller that activates all controllers at once by
clicking on the object should be sufficient. All controllers that act on a
single object should be able to coexist. This implies that controllers do
not register for all
VectorObjectContainer events but instead
delegate their work to specific helper objects like resize handlers, drag
masks or special icons (e.g. to activate a specific editor).
GraphicsService is a manager class that manages the
GraphicsObjectContainer, instantiates the
GraphicsObjectController objects (and acts a registry for
their factories) and executes
GraphicsOperations on the
GraphicsObject instances. A
undoable and redoable by keeping sufficient information to restore the
object state to what it was before the operation.
In order to use this project through Maven, use the following dependency:
<dependency> <groupId>org.geomajas.project</groupId> <artifactId>geomajas-project-graphics</artifactId> <version>1.0.0-M5</version> </dependency>
For those not using Maven, this project depends on the Geomajas annotation project.