The new 'session_control' function can be used to perform operations on
the global view stack that span one or multiple sessions, e.g., bringing
all views of specific sessions to the front, or hiding them.
This patch introduces a mandatory layer attribute to domains. The layer
ordering is superimposed on the stacking order of the views. The
top-most layer can be assigned to a pointer-managing client. An example
for such a pointer is located at os/src/app/pointer. It replaces the
formerly built-in nitpicker mouse cursor.
The new layering mechanism replaces the former "stay-top" session
argument. So the Nitpicker::Connection no longer takes the stay-top flag
as the first argument.
This patch changes nitpicker's session interface to use session-local
view handles instead of view capabilities. This enables the batching
of multiple view operations into one atomic update.
This patch changes nitpicker's way of redrawing. Originally, redraw
operations were triggered immediately by the RPC functions invoked by
clients. In the presence of clients that invoked a large number of those
functions, the server could become overloaded with processing redraw
operations. The new version performs redraw operations out of band with
the RPC functions. Similar to the design of the DOpE GUI server, redraw
operations are processed periodically. The RPC functions merely modify
meta data and track the dirty areas that need to be updated.
Consequently, nitpicker's RPC functions become light-weight operations.
As a nice collateral effect of this patch, nitpicker's internal
structure could be simplified because the drawing backend is no longer
needed by the code that dispatches the RPC interface.
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
