How would one use IDecorationContext api from Eclipse JFace

api, eclipse, java, jface, swt

Solution

I did not use IDecorationContext, but you can see it used in `org.eclipse.jface.viewers.LabelDecorator`.

It is also discussed in this thread (even if there are no answer, that can at least give you a starting point)

My current approach is to extend org.eclipse.ui.decorators using a ILightweightLabelDecorator to add a replace overlay to the respective icons:

public class ProjectLabelDecorator extends LabelProvider 
   implements ILightweightLabelDecorator {

   ...

   public void decorate(Object element, IDecoration decoration) {
      if (element instanceof IFolder) {
         IFolder folder = (IFolder) element;
     try {
            if (folder.getProject().hasNature("rttdt.nature")) {
                if (ProjectNature.isTestcase(folder)) {
                   IDecorationContext context = 
                      decoration.getDecorationContext();
                   if (context instanceof DecorationContext) {
                      ((DecorationContext) context).putProperty(
                         IDecoration.ENABLE_REPLACE, Boolean.TRUE);
                   }
                   decoration.addOverlay(fTestcaseOverlay,
                      IDecoration.REPLACE);
                }
         } catch (CoreException e) {
         }
      }
   }

   ...
}

Problem

Is there an example out there for using `IDecorationContext` for label decorations? By the looks of it, `IDecorationContext` class seems to provide some sort of contextual decoration support, but for the life of me, I can not find any sample code using this feature... Has anybody actually used decoration context feature and if so, what use cases did it solve? PS: I am looking for a way to apply image decorations to object labels and depending on where the object is displayed, the base icon size varies (e.g. traditional "small" icons in table- and tree items and larger icons for content headers). The decorations applied to the original icons should choose appropriate size decorations accordingly. `IDecorationContext` seems to fit the bill for what I need it for, but the documentation is as sparse as one can expect from a minor feature of an open source library and there are no examples to be found. Googling for the "IDecorationContext" did not reveal anything interesting either, so I turn to StackOverflow crowd wisdom in hopes next guy getting the question would be able to get their answer faster ;)

Original source