Eclipse GEF - Snap to Grid not working - eclipse-rcp

Question

I am trying to use the "Snap to Grid" function for a GEF viewer. I am following the tutorial at this site. The tutorial essentially talks about installing necessary edit policies and overriding the getAdapter method like below:
#Override
public Object getAdapter(Class key) {
System.out.println("snapping..." + key);
if (key == SnapToHelper.class) {
List<SnapToHelper> helpers = new ArrayList<SnapToHelper>();
if (Boolean.TRUE.equals(getViewer().getProperty(
SnapToGeometry.PROPERTY_SNAP_ENABLED))) {
helpers.add(new SnapToGeometry(this));
}
if (Boolean.TRUE.equals(getViewer().getProperty(
SnapToGrid.PROPERTY_GRID_ENABLED))) {
helpers.add(new SnapToGrid(this));
}
if (helpers.size() == 0) {
return null;
} else {
return new CompoundSnapToHelper(
helpers.toArray(new SnapToHelper[0]));
}
}
return super.getAdapter(key);
}
However during runtime, the getAdapter method is never called with a SnapToHelper instance which I confirmed by putting a println method.
am I missing something?

Answer 1

After some research, I learnt that I had made a trivial mistake which took me several days to figure out. The code snippet of createFigure method for a typical TopEditPart is as follows:
protected IFigure createFigure() {
Figure f = new FreeformLayer();
f.setLayoutManager(new FreeformLayout());
f.setBorder(new MarginBorder(1));
// Create a layout for the graphical screen
f.setOpaque(true);
helpers = new ArrayList<SnapToHelper>();
helpers.add(new SnapToGrid(this));
CompoundSnapToHelper h = new CompoundSnapToHelper(
helpers.toArray(new SnapToHelper[0]));
return f;
}
In the above method, using f.setOpaque(true); had hidden the grid all this while and had cost me several days to figure out. I have now changed it to f.setOpaque(false); and now I am able to see the grid. Hope many could save time because of this answer.