Restore ability to modify selection in GroupRequest within DeleteAction

[ptziegler]

The list returned by getSelectedEditParts() should be a view of the internal selection, similar to getSelectedObjects(). Meaning callers are able to modify by the selection by calling set(int,Object).

In order to reduce the chance of an undesirable ClassCastException, we only check whether the first element in the list is an EditPart, assuming that all remaining elements are as well. I.e. we don't expect a "mixed" selection of different types. This is similar to what has already been done in e.g. the DeleteAction or the MatchSizeAction.

This is a follow-up to 78c3fed.

Resolves #616

[ptziegler]

The lazy check with objects.get(0) I mentioned:

gef-classic/org.eclipse.gef/src/org/eclipse/gef/ui/actions/DeleteAction.java

Lines 93 to 115 in 4660b69

	@SuppressWarnings("static-method")
	public Command createDeleteCommand(List objects) {
	if (objects.isEmpty()) {
	return null;
	}
	if (!(objects.get(0) instanceof EditPart)) {
	return null;
	}
	GroupRequest deleteReq = new GroupRequest(RequestConstants.REQ_DELETE);
	deleteReq.setEditParts(objects);
	CompoundCommand compoundCmd = new CompoundCommand(GEFMessages.DeleteAction_ActionDeleteCommandName);
	for (Object object2 : objects) {
	EditPart object = (EditPart) object2;
	Command cmd = object.getCommand(deleteReq);
	if (cmd != null) {
	compoundCmd.add(cmd);
	}
	}
	return compoundCmd;
	}

gef-classic/org.eclipse.gef/src/org/eclipse/gef/ui/actions/MatchSizeAction.java

Lines 72 to 119 in 4660b69

	private Command createMatchSizeCommand(List objects) {
	if (objects.isEmpty()) {
	return null;
	}
	if (!(objects.get(0) instanceof GraphicalEditPart)) {
	return null;
	}
	GraphicalEditPart primarySelection = getPrimarySelectionEditPart(getSelectedObjects());
	if (primarySelection == null) {
	return null;
	}
	GraphicalEditPart part = null;
	ChangeBoundsRequest request = null;
	PrecisionDimension preciseDimension = null;
	PrecisionRectangle precisePartBounds = null;
	Command cmd = null;
	CompoundCommand command = new CompoundCommand();
	PrecisionRectangle precisePrimaryBounds = new PrecisionRectangle(
	primarySelection.getFigure().getBounds().getCopy());
	primarySelection.getFigure().translateToAbsolute(precisePrimaryBounds);
	for (Object object : objects) {
	part = (GraphicalEditPart) object;
	if (!part.equals(primarySelection)) {
	request = new ChangeBoundsRequest(RequestConstants.REQ_RESIZE);
	precisePartBounds = new PrecisionRectangle(part.getFigure().getBounds().getCopy());
	part.getFigure().translateToAbsolute(precisePartBounds);
	preciseDimension = new PrecisionDimension();
	preciseDimension.setPreciseWidth(getPreciseWidthDelta(precisePartBounds, precisePrimaryBounds));
	preciseDimension.setPreciseHeight(getPreciseHeightDelta(precisePartBounds, precisePrimaryBounds));
	request.setSizeDelta(preciseDimension);
	cmd = part.getCommand(request);
	if (cmd != null) {
	command.add(cmd);
	}
	}
	}
	return command;
	}

[merks]

This is an API breaking change and break BIRT's build:

eclipse-birt/birt#1972 (comment)

Please revert it.