So we\'re re-designing a desktop application so that it\'s also usable with thye Touch Interface with Windows 7. We\'ve consulted the UX guidelines.
For some part of
One option is to leave the control enabled and show a message when it is clicked to say why it won't do anything. However as stated in 'Disabled Menus Are Usable' this throws away valuable information for an experienced user (although this is less of an issue for icons than menus as there are usually less icons to go through than menus).
Another possibility is to provide a control like the click for help tools that were popular a few years ago. The user would first click on the 'why is this disabled' control, then click on the control that is disabled. This is however a rather clunky solution.
Another problem with toolbox icons on a touch interface is that the tooltip text is often essential as it is often impossible to convey complex/domain-specific actions with an icon. i would imagine many users on a touch only device will just use the menus instead as they can work out what they will do.
Not an official solution but here's how I'll approach this until a better solution is available: