I've just released code that supports
undo of marker operations, such as creating, deleting, and updating tasks
In tonight's nightly build and beyond
(but not in today's I-build), you should be able to undo these operations
from both the associated view (task list, bookmark view) as well as the
package explorer or resource navigator.
I'd also like to encourage any plug-ins
that define their own marker operations to consider adopting this support.
I can help get you started, or in some cases supply patches if I
already understand your code. The API classes are defined in org.eclipse.ui.ide.undo.
They are marked experimental for now. The basic idea for clients
is that instead of calling the core.resources API to create, update, or
delete a marker, you instead create an undoable operation (such as a CreateMarkersOperation,
UpdateMarkersOperation, etc.). that describes what you want to do. Executing
this operation will perform the operation, catch and handle the CoreExceptions,
and make the undo for the operation available.
Please see the following bug for more
info, and open any new bugs on the feature against Platform UI with
[Undo] in the title.