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GEF/GEF4/Zest

< GEF‎ | GEF4

Note to non-wiki readers: This documentation is generated from the Eclipse wiki - if you have corrections or additions it would be awesome if you added them in the original wiki page.


Introduction

The GEF4 Zest component provides support for visualizing GEF4 Graph-based graph models, applying automatic layout as provided by GEF4 Layout. It is internally decomposed into the Zest.FX and Zest.FX.UI modules. In addition, there is a deployed Zest Graph Example as well as some undeployed Zest UI examples.

GEF4-Components-Zest.png

Zest.FX

  • feature: org.eclipse.gef4.zest.fx
  • bundle: org.eclipse.gef4.zest.fx

The Zest.FX module of GEF4 Zest provides a graph viewer and implements all functionality therefore. It uses JavaFX and GEF4 FX for visualization purposes and is internally based on GEF4 MVC, can thus also be used standalone. Integrating with the Eclipse UI is realized by the Zest.FX.UI module.

{Root}

  • package: org.eclipse.gef4.zest.fx

The {Root} package provides a com.google.inject.Module (ZestFxModule) with bindings, as well as a utility class to work with the visualization and layout attributes/properties recognized by GEF4 Zest (ZestProperties).

GEF4-Zest-FX-root.jpg

ZestFxModule

The ZestFxModule defines various (default) bindings, concerning parts, policies, etc. needed to realize the graph visualization.

ZestProperties

ZestProperties defines attributes that are associated to graphs, nodes, and edges (of GEF4 Graph), to control the visualization as well as the layout.

The visualization is based on the following attributes that are associated with graphs, nodes, or edges:

The following attributes are evaluated for graphs:

  • "type": Stores a String specifying whether the graph is "directed" or "undirected". In a directed graph, every edge represents a unidirectional connection between its source and target nodes, whereas in an undirected graph, every edge represents a bidirectional connection between its source and target nodes.

The following attributes are evaluated for nodes and edges (referred to as elements):

  • "css-class": Stores the CSS class (String) that is assigned to this element.
  • "css-id": Stores the CSS id (String) that is assigned to this element.
  • "label": Stores the label (String) for this element.

The following attributes are evaluated for nodes:

  • "node-rect-css-style": Stores the CSS style (String) that is assigned to the JavaFX Rectangle which displays the border and background of this node.
  • "node-label-css-style": Stores the CSS style (String) that is assigned to the JavaFX Text which displays the label of this node.
  • "icon": JavaFX Image which is displayed next to the node's label.
  • "tooltip": Text (String) which is shown as a tooltip, i.e. when the mouse hover the node and does not move for a short time.
  • "fisheye": If set to True (Boolean), the node's visualization is reduced to a minimum and only expands when the mouse is over the node.

The following attributes are evaluated for edges:

  • "edge-curve-css-style": Stores the CSS style (String) that is assigned to the FXGeometryNode<ICurve> (GEF4 FX) which displays this edge.
  • "edge-label-css-style": Stores the CSS style (String) that is assigned to the JavaFX Text which displays the label of this edge.
  • "edge-router": Stores an IFXConnectionRouter (GEF4 FX) that is used to compute the ICurve (GEF4 Geometry) which is used as the basis for the visualization of this edge.
  • "style": Stores a String specifying the dash pattern of the edge, which can be "solid", "dashed", "dotted", "dashdot", or "dashdotdot".

The layout is based on the following attributes that are associated with graphs, nodes, or edges:

The following attributes are evaluated for graphs:

  • "layout": Stores the ILayoutAlgorithm (see GEF4 Layout) that will be used to layout the nodes and edges of this graph.

The following attributes are evaluated for nodes and edges (referred to as elements):

  • "layout-irrelevant": If set to True (Boolean), this element will not get layed out.

Behaviors

  • package: org.eclipse.gef4.zest.fx.behaviors

GEF4-Zest-FX-behaviors.png


Layout

  • package: org.eclipse.gef4.zest.fx.layout

GEF4-Zest-FX-layout.png

GraphLayoutContext, GraphNodeLayout, GraphEdgeLayout, GraphSubgraphLayout

The GEF4 Layout interfaces are adopted to the GEF4 Graph data model. The layout objects are constructed from a given Graph object. The layout objects support a general property mechanism to exchange layout information. GEF4 Zest transfers visualization attributes (locations and sizes) to layout properties and vice versa. A GraphLayoutContext combines all layout information for one Graph. Therefore, one GraphLayoutContext is maintained per GraphContentPart via the adapter mechanism.

You can access the GraphLayoutContext for a specific Graph as follows:

GraphLayoutContext layoutContext = viewer.getContentPartMap().get(graph).getAdapter(LayoutModel.class);

Models

  • package: org.eclipse.gef4.zest.fx.models

GEF4-Zest-FX-models.png

HidingModel

A HidingModel stores which nodes are currently hidden. Every visible node shows a small marker indicating how many of its neighbors are hidden. You can hide/show nodes using the hover handles, respectively. The visualization is automatically synchronized with the HidingModel.

Hover handles for hide/show

LayoutModel

ViewportStackModel


Operations

  • package: org.eclipse.gef4.zest.fx.operations

GEF4-Zest-FX-operations.png


Parts

  • package: org.eclipse.gef4.zest.fx.parts

GEF4-Zest-FX-parts-root.png

GEF4-Zest-FX-parts-contents.png

GEF4-Zest-FX-parts-feedback.png

GEF4-Zest-FX-parts-handles.png

GEF4-Zest-FX-parts-providers.png

The GEF4 MVC component is used as the framework for the viewer. It is extended by implementing content parts for the GEF4 Graph data model (GraphContentPart, NodeContentPart, and EdgeContentPart) and binding a separate content part factory for it, integrating the GEF4 Layout component (layout integration), and implementing hiding of nodes by providing a HidingModel and corresponding policies and behaviors.

The GEF4 Graph data model consists of 3 classes: Graph, Node, and Edge. A Graph serves as a container for Nodes and Edges. Additionally, a Graph can be nested inside a so called nesting Node. Moreover, arbitrary attributes can be set on Graphs, Nodes, and Edges, which the visualization is based on (ZestProperties). GEF4 Zest expects a Graph as its input, which is stored in the ContentModel provided by GEF4 MVC. A separate content part is created for every Graph, Node, or Edge in the ContentModel and the content parts are automatically synchronized with the ContentModel, i.e. content parts are removed, created, or refreshed according to ContentModel changes. The content parts are utilized for the synchronization and are also responsible for the visualization of their corresponding content objects.

GEF4 Zest default visuals

The default visualization for nodes consists of a JavaFX Rectangle for background and border, a Text for the label, and an ImageView for the icon. The default visualization for edges consists of an FXGeometryNode<ICurve> for the connection line, and a JavaFX Text for the label.

GraphRootPart

GraphContentPart, NodeContentPart, EdgeContentPart, EdgeLabelPart, ContentPartFactory

ZestFxHidingHandlePart, ZestFxExpandingHandlePart, ZestFxHandlePartFactory

Please note that the 'ZestFx' prefix will probably be removed in the future.

HiddenNeighborsPart, ZestFxEdgeLinkFeedbackPart, ZestFxFeedbackPartFactory

Please note that the 'ZestFx' prefix will probably be removed in the future.

ZestCursorProvider


Policies

  • package: org.eclipse.gef4.zest.fx.policies

GEF4-Zest-FX-policies.png


Zest.FX.UI

  • feature: org.eclipse.gef4.zest.fx.ui
  • bundle: org.eclipse.gef4.zest.fx.ui

The Zest.FX.UI module of GEF4 Zest contains all Eclipse Workbench UI integration aspects.


{Root}

  • package: org.eclipse.gef4.zest.fx.ui

GEF4-Zest-FX-UI-root.png

ZestFxUiModule


JFace

  • package: org.eclipse.gef4.zest.fx.ui.jface

GEF4-Zest-FX-UI-jface.png

ZestContentViewer


Parts

  • package: org.eclipse.gef4.zest.fx.ui.parts

The Parts package provides an Eclipse ViewPart (ZestFxUiView) for visualizing graph models, so that you can integrate it into the Eclipse workbench.

GEF4-Zest-FX-UI-parts.png

ZestFxUiView

ZestFxUiView is a specific FXView that can render graphs. It uses the bindings provided by ZestFxUiModule.

GEF4 Zest in Eclipse


Migration from Zest 1.x to GEF4 Zest

GEF4 Zest was mostly written from scratch, replacing the Zest 1.x API as well as the provisional Zest 2.x API ( Zest 2.0 Layout API) that was developed as an intermediate step.

The Zest 1.x API consists of two parts:

  1. a core API for the visualization of graphs, and
  2. a JFace API with specific content and label providers and a viewer dedicated to displaying Zest graphs.

The former has been replaced by GEF4 Zest.FX and the latter by Zest.FX.UI.


Migration from Zest 1.x Core to GEF4 Zest.FX

In comparison to the Zest 1.x Core API, which is based on SWT/Draw2d visualization and interweaves graph data, layout data, and visuals, Zest.FX is based on GEF4 MVC and maintains distinct object hierarchies for the graph data (content model), the layout data (layout model), and the visuals. As a result, in order to perform structural changes to the visualized graph, you cannot directly affect the visualization as in Zest 1.x Core, but instead modify the underlying graph model which will effect a content synchronization, i.e. update the visualization based on the content changes. Therefore, to transition from Zest 1.x Core to Zest.FX, you have to create/modify a GEF4 Graph where previously Zest 1.x Graph, GraphNode, and GraphConnection were created/modified.

Since Zest.FX is based on GEF4 MVC, you should be familiar with the mechanisms and concepts of GEF4 MVC, which are employed as follows:

  • A org.eclipse.gef4.mvc.models.ContentModel stores the Graph that is currently rendered.
  • A org.eclipse.gef4.mvc.parts.IContentPartFactory (ContentPartFactory) constructs controller objects (content parts) for graphs, nodes, and edges. These are responsible for updating the visualization, synchronizing visualizations with contents, and layout integration.
  • All content parts support an adapter mechanism where you can set/query adapters for distinct keys. Functionality can be added to a content part by setting a corresponding adapter on it. For example, you can enable different interactions (moving nodes via drag, etc.) by setting the corresponding policies as adapters on the content parts.
  • A com.google.inject.Module] (ZestFxModule) defines bindings for the context of an application. Using this mechanism, you can specify which adapters should be set on the different content parts. For example, the adapter mechanism is used to integrate GEF4 Layout into GEF4 Zest.

The Zest Graph Example demonstrates best how to use the new API. The example is very simple as the rendered graph is not modified later on. However, it contains everything that is needed for a fully functional example. As you can see when taking a look into the source code, attributes are set on the graph model to specify certain visualization features such as label, tooltip, CSS id, etc. Actually, the whole visualization results from those attributes (Visualization Properties).

Some specific Zest 1.x core functionalities are implemented differently within Zest.FX. The corresponding use case scenerios are as follows.

Customizing Styles

Many visual features can be specified via JavaFX CSS within GEF4 Zest which would have required either a style provider or a custom figure in previous versions. The CSS styles can be applied to individual elements, or entire classes of elements. There are four parts of the visualization which can be styled individually:

  • "node-rect-css-style": Styles the JavaFX Rectangle which renders the border and background of a node.
  • "node-label-css-style": Styles the JavaFX Text which renders the label of a node.
  • "edge-curve-css-style": Styles the FXGeometryNode which renders an edge.
  • "edge-label-css-style": Styles the JavaFX Text which renders the label of an edge.

Customizing Visualizations

Within GEF4 MVC, on which Zest.FX is based, an org.eclipse.gef4.mvc.parts.IContentPart is responsible of contributing a respective visualization. You can exchange the org.eclipse.gef4.mvc.parts.IContentPart that is provided by Zest.FX to control nodes and edges, and thereby replace their visualizations. Zest.FX uses an own (ContentPartFactory) to create content parts for graph elements. Therefore, you have to exchange this ContentPartFactory to be able to create custom content parts. The ZestFxModule contains a binding for the ContentPartFactory. You have to create an own module by subclassing it, overriding the corresponding bindIContentPartFactory() to bind your custom org.eclipse.gef4.mvc.parts.IContentPartFactory instead. Within the custom org.eclipse.gef4.mvc.parts.IContentPartFactory, you can then construct your custom content parts, for example, for graph elements with specific attributes. The JFaceCustomNodeExample demonstrates this scenario. However, be aware that colors, fonts, borders, and sizes can already be configured via JavaFX CSS and do not require a custom visualization, as outlined in Customizing Styles.

Modifying graphs

Since you cannot modify the visualization directly, you have to adjust the underlying graph model instead. The FullyMeshedLayoutExample demonstrates this scenario.

Layout filter

Nodes and edges can be marked as layout-irrelevant, meaning they will not get reported to layout algorithms. The FilterLayoutExample demonstrates this scenario.


Migration from Zest 1.x JFace to GEF4 Zest.FX.UI

Zest.FX.UI consists of a ZestContentViewer and related specializations of org.eclipse.jface.viewers.IContentProvider and org.eclipse.jface.viewers.ILabelProvider. In comparison to the org.eclipse.zest.core.viewers.GraphViewer, the ZestContentViewer is not a org.eclipse.jface.viewers.StructuredViewer, but a org.eclipse.jface.viewers.ContentViewer, which seems to be the more adequate abstraction (as a structured viewer imposes a tree-, list-, or table-based structure, which does not naturally resemble a graph).

Content Providers

Probably, the biggest difference between the Zest 1.x JFace API and Zest.FX.UI is related to content providers. Zest.FX defines the following ones:

  • The IGraphNodeContentProvider provides all content elements that represent nodes for a flat graph. The edges are inferred via a getConnectedTo(Object) method. This is the equivalent of the Zest 1.x IGraphEntityContentProvider.
  • The INestedGraphContentProvider extends the IGraphNodeContentProvider by two methods to provide nested graphs. This is the equivalence of the Zest 1.x INestedContentProvider.

So, both new content providers are node-oriented, i.e. they provide content elements which represent nodes, not edges. The Zest 1.x API additionally defines an IGraphEntityRelationshipContentProvider which provides content elements that represent edges, which is not covered by Zest.FX.UI.

Label Providers

While Zest 1.x was based on the default org.eclipse.jface.viewers.ILabelProvider, Zest.FX.UI provides two specializations, namely IGraphNodeLabelProvider and INestedGraphLabelProvider. They allow to provide attributes for graphs, nodes, edges, and nested graphs, which may also overwrite those values provided by a dedicated provider.

Dedicated Providers for Styles, Tooltip, Colors, Fonts

Most of the custom Zest 1.x JFace providers have been replaced with the respective standard JFace providers:

The values returned by a provider for the font, foreground, and background color are transferred into equivalent CSS styles which can be overwritten by an IGraphNodeLabelProvider or INestedGraphLabelProvider.

The following providers have not been migrated, because their corresponding functionality is implemented by means of default GEF4 MVC mechanisms, on which Zest.FX and thus Zest.FX.UI are based:

You can find examples on how to use the different providers in the JFace-API examples.

Zooming

Basic support for zooming, which is specifically implemented within org.eclipse.zest.core.viewers.GraphViewer, is already provided as a base feature of GEF4 MVC.FX, on which Zest.FX and thus also Zest.FX.UI are based. Within GEF4 MVC, a ViewportModel maintains a content transformation which can be modified to zoom in/out of a visualization. Zest.FX adds a semantic zoom that allows to zoom into nested graphs. That is, when zooming into a nesting node, it will - from a certain zoom level onwards - show the nested contents and will eventually replace the viewer contents with the nested graph.