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<h1>Providing Layout Functionality</h1>
<h2>Create a Layout Feature</h2>
<p>If you already enlarged a EClass in the diagram, you may have observed that the
shapes inside the rectangle kept their size (EClass name is not longer in the centre
and the line separator is too short). Graphiti provides the concept of layout features,
which mainly supports the recalculation of positions and sizes inside the pictogram
model. </p>
<p>Theoretical such functionality could also be implemented by
<a href="resize-feature.htm">providing resize functionality</a>, but using a layout
feature for this is the recommended solution.</p>
<p>A layout feature has to implement the interface
<a href="../../../javadoc/org/eclipse/graphiti/features/ILayoutFeature.html">ILayoutFeature</a>.
Instead of implementing it directly you should extend one of the available base
classes. In this example we extend the base class
<a href="../../../javadoc/org/eclipse/graphiti/features/impl/AbstractLayoutFeature.html">
AbstractLayoutFeature</a>.</p>
<p>In this case we have to implement/overwrite two methods:</p>
<ul>
<li>The method
<a href="../../../javadoc/org/eclipse/graphiti/func/ILayout.html#canLayout(org.eclipse.graphiti.features.context.ILayoutContext)">
canLayout</a> has to check whether the pictogram element of the given context
can be layouted. </li>
<li>The method
<a href="../../../javadoc/org/eclipse/graphiti/func/ILayout.html#layout(org.eclipse.graphiti.features.context.ILayoutContext)">
layout</a> has to recalculate and modify everything needed to layout the pictogram
element given with the context. </li>
</ul>
<p>You can see the complete implementation of the move feature here:</p>
<p>&nbsp;</p>
<div class="literallayout">
<div class="incode">
<p class="code"><span class="keyword">package </span>org.eclipse.graphiti.examples.tutorial.features;<br>&nbsp;<br>
<span class="keyword">public class</span> TutorialLayoutEClassFeature
<span class="keyword">extends </span>AbstractLayoutFeature {<br>&nbsp;<br>&nbsp;&nbsp;&nbsp;
<span class="keyword">private static final int</span>
<span class="string"><em>MIN_HEIGHT</em> </span>= 30;<br>&nbsp;<br>&nbsp;&nbsp;&nbsp;
<span class="keyword">private static final int</span>
<span class="string"><em>MIN_WIDTH</em></span> = 50;<br>&nbsp;<br>&nbsp;&nbsp;&nbsp;
<span class="keyword">public </span>TutorialLayoutEClassFeature(IFeatureProvider
fp) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">super</span>(fp);<br>&nbsp;&nbsp;&nbsp; }<br>&nbsp;<br>&nbsp;&nbsp;&nbsp;
<span class="keyword">public boolean</span> canLayout(ILayoutContext context)
{<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <span class="comment">// return
true, if pictogram element is linked to an EClass</span><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
PictogramElement pe = context.getPictogramElement();<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">if </span>(!(pe <span class="keyword">instanceof
</span>ContainerShape))<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">return false</span>;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
EList&lt;EObject&gt; businessObjects = pe.getLink().getBusinessObjects();<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">return </span>businessObjects.size() == 1 <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&amp;&amp; businessObjects.get(0) <span class="keyword">instanceof </span>EClass;<br>&nbsp;&nbsp;&nbsp;
}<br>&nbsp;<br>&nbsp;&nbsp;&nbsp; <span class="keyword">public boolean</span>
layout(ILayoutContext context) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">boolean </span>anythingChanged =
<span class="keyword">false</span>;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
ContainerShape containerShape =<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
(ContainerShape) context.getPictogramElement();<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
GraphicsAlgorithm containerGa = containerShape.getGraphicsAlgorithm();<br>&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="comment">// height</span><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">if </span>(containerGa.getHeight() &lt;
<span class="string"><em>MIN_HEIGHT</em></span>) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
containerGa.setHeight(<span class="string"><em>MIN_HEIGHT</em></span>);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
anythingChanged = <span class="keyword">true</span>;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
}<br>&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="comment">// width</span><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">if </span>(containerGa.getWidth() &lt;
<span class="string"><em>MIN_WIDTH</em></span>) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
containerGa.setWidth(<span class="string"><em>MIN_WIDTH</em></span>);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
anythingChanged = <span class="keyword">true</span>;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
}<br>&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">int </span>containerWidth = containerGa.getWidth();<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <span class="keyword">for
</span>(Shape shape : containerShape.getChildren()){<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
GraphicsAlgorithm graphicsAlgorithm = shape.getGraphicsAlgorithm();<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
IGaService gaService = Graphiti.getGaService();<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
IDimension size = <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
gaService.calculateSize(graphicsAlgorithm);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">if </span>(containerWidth != size.getWidth()) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">if</span> (graphicsAlgorithm <span class="keyword">
instanceof </span>Polyline) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
Polyline polyline = (Polyline) graphicsAlgorithm;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
Point secondPoint = polyline.getPoints().get(1);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
Point newSecondPoint =<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
gaService.createPoint(containerWidth, secondPoint.getY()); <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
polyline.getPoints().set(1, newSecondPoint);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
anythingChanged = <span class="keyword">true</span>;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
} <span class="keyword">else </span>{<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
gaService.setWidth(graphicsAlgorithm,<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
containerWidth);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
anythingChanged = <span class="keyword">true</span>;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
}<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
}<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">return </span>anythingChanged;<br>&nbsp;&nbsp;&nbsp;
}<br>}<br></p>
</div>
</div>
<p>&nbsp;</p>
<p>Additionally the feature provider has to deliver our newly created feature (overwrite
the method
<a href="../../../javadoc/org/eclipse/graphiti/features/IFeatureProvider.html#getLayoutFeature(org.eclipse.graphiti.features.context.ILayoutContext)">
getLayoutFeature</a>).</p>
<p>This implementation can be seen here:</p>
<p>&nbsp;</p>
<div class="literallayout">
<div class="incode">
<p class="code">@Override<br><span class="keyword">public </span>ILayoutFeature
getLayoutFeature(ILayoutContext context) {<br>&nbsp;&nbsp;&nbsp; PictogramElement
pictogramElement = context.getPictogramElement();<br>&nbsp;&nbsp;&nbsp;
Object bo = getBusinessObjectForPictogramElement(pictogramElement);<br>&nbsp;&nbsp;&nbsp;
<span class="keyword">if</span> (bo <span class="keyword">instanceof</span>
EClass) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">return new</span> TutorialLayoutEClassFeature(<span class="keyword">this</span>);<br>&nbsp;&nbsp;&nbsp;
}<br>&nbsp;&nbsp;&nbsp; <span class="keyword">return super</span>.getLayoutFeature(context);<br>
} </p>
</div>
</div>
<p>&nbsp;</p>
<p>Finally we have to call the layout feature at the end of the add method of the
<span class="incode"><em>TutorialAddEClassFeature</em></span>, as shown in the following
code snippet.</p>
<p>This causes that the layout (especially the layout restrictions like minimum
size) are applied after adding a EClass.</p>
<p>&nbsp;</p>
<div class="literallayout">
<div class="incode">
<p class="code">&nbsp;<span class="keyword">public </span>PictogramElement
add(IAddContext context) {<br>&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <span class="comment">//
... EXISTING CODING ...</span><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="comment">// call the layout feature</span><br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
layoutPictogramElement(containerShape);<br>&nbsp;<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<span class="keyword">return </span>containerShape;<br>&nbsp;&nbsp;&nbsp;
}&nbsp; </p>
</div>
</div>
<p>&nbsp;</p>
<h2>Test: Layout EClass after Resize</h2>
<p>Now start the editor again and test it: Try to resize a EClass. You see that
the class name stays in the centre and the line separator will be automatically
extended.</p>
</body>
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