Abstract: User interaction with multiple domains is facilitated while preventing cross-domain transfer of data from those domains. A compositioning domain facilitates this interaction in a secure manner in which cross-domain transfer of data is prevented. This includes obtaining pixel information from the domains via one or more read-only communication paths, providing a user interface to the user, which includes providing a display buffer including at least some of the pixel information obtained from each domain of the domains for display to the user, and maintaining an in-focus domain state. The in-focus domain state indicates which domain of the domains is currently in-focus. User input from the user based on the user interface is provided by a user input handler directly to the currently in-focus domain indicated by the in-focus domain state absent transfer of the user input to the compositioning domain.

Abstract: A crowd control mechanism for a power shovel includes an extendible dipper handle having an extended position and a retracted position. A double acting hydraulic cylinder having a an extendible ram has one of the cylinder and the ram fixed to the dipper handle and the other of the cylinder and the ram is stationary relative to the dipper handle. At least one of the cylinder and the ram have at least one of a blind end port and a rod end port, and at least one of the cylinder and the ram have the other of the blind end port and the rod end port, wherein hydraulic fluid flowing into the cylinder through the blind end port urges the ram toward an extended position to extend the dipper handle, and hydraulic fluid flowing into the rod end port urges the ram toward a retracted position to retract the dipper handle. Hydraulic fluid flowing into and out of the cylinder is controlled by one or more pilot operated poppet valves.