no way to center label

Question

When an edge is a spline, there is no way to add a label to it that is centered and placed over the edge. See this graph as an example:

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  <key attr.name="url" attr.type="string" for="node" id="d4"/>
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  <key for="node" id="d6" yfiles.type="nodegraphics"/>
  <key attr.name="Description" attr.type="string" for="graph" id="d7"/>
  <key attr.name="url" attr.type="string" for="edge" id="d8"/>
  <key attr.name="description" attr.type="string" for="edge" id="d9"/>
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          <y:Fill hasColor="false" transparent="false"/>
          <y:BorderStyle color="#000000" type="line" width="1.0"/>
          <y:NodeLabel alignment="center" autoSizePolicy="content" fontFamily="Dialog" fontSize="12" fontStyle="plain" hasBackgroundColor="false" hasLineColor="false" hasText="false" height="4.0" modelName="internal" modelPosition="c" textColor="#000000" visible="true" width="4.0" x="13.0" y="13.0"/>
          <y:Shape type="ellipse"/>
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          <y:Fill hasColor="false" transparent="false"/>
          <y:BorderStyle color="#000000" type="line" width="1.0"/>
          <y:NodeLabel alignment="center" autoSizePolicy="content" fontFamily="Dialog" fontSize="12" fontStyle="plain" hasBackgroundColor="false" hasLineColor="false" hasText="false" height="4.0" modelName="internal" modelPosition="c" textColor="#000000" visible="true" width="4.0" x="13.0" y="13.0"/>
          <y:Shape type="ellipse"/>
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    </node>
    <edge id="e0" source="n1" target="n0">
      <data key="d9"/>
      <data key="d10">
        <y:SplineEdge>
          <y:Path sx="0.0" sy="0.0" tx="0.0" ty="0.0">
            <y:Point x="520.0" y="421.5"/>
          </y:Path>
          <y:LineStyle color="#000000" type="dashed" width="1.0"/>
          <y:Arrows source="none" target="standard"/>
          <y:EdgeLabel alignment="center" backgroundColor="#FFFFFF" distance="2.0" fontFamily="Dialog" fontSize="12" fontStyle="plain" hasLineColor="false" height="18.701171875" modelName="centered" modelPosition="center" preferredPlacement="anywhere" ratio="0.5" textColor="#000000" visible="true" width="10.673828125" x="49.28985595703125" y="126.40604874894422">a</y:EdgeLabel>
        </y:SplineEdge>
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Answer 1

That's not entirely true. In short, the label model of your edge label is Centered which doesn't work very well with non-straight line edges. You can change this to, for example, the Free (unrestricted) label model in the Properties View.

For convenience, I propose to create an edge with a label position that fits your needs and add it as template to a user-defined palette section.

Please see the following links for more details:

• Discussion about label models
• yEd Manual: Palette

 

Comments

The FREE placement has much the same problems as the CENTERED one:
the label does not remain placed over the edge when the edge is redrawn (e.g. bent).

Answer 2

Label placement always assumes a straight-line edge path. Moreover, center position has strange semantics and only works as expected for edges without bends. (If there are bends, center places the label near the middle of the edge's longest straight-line segement.)