It was obviously very wrong to use both a unique_ptr to the
MasterProcessSession in WebSocketRequestHandler::handleRequest(), and then a
bare pointers to the peer object in the MasterProcessSession object. We got
crashes here and there related to the destructors.
Let's see if we can manage without mutexes.
There probably are more places where I should catch those and act
appropriately. At least in these places, where the websocket connection is
already closed, or being closed, anyway, the right thing to do is just to
ignore exceptions, which are generated from attempts to write to an already
closed Poco WebSocket, for instance.
Also, seems that calling LOKitDocument::destroy() (in the child process's
LOOLSession dtor) causes crashes, avoid that. The can be little need for any
cleanup as the process is about to exit anyway, and the user profile is a
temporary one that will be binned.
But actually I wonder why I thought I would need signalfd at all; wouldn't it
be enough to just loop in the undertaker thread, calling waitpid(), as long as
there are child processes? I'll try after this commit.
(Besides, I now notice that when I client disconnects, we don't close the
websocket to the child process, so it never goes away. Will fix that.)
As the child processes are pre-spawned and just hang around waiting, there is
ample time to attach one in a debugger in a controlled debugging scenario
anyway.
Otherwise it uses a timestamp with one-second granularity as seed, and thus
most of the child processes pre-spawned at start will use the same seed, which
causes breakage.
Works now for the trivial 'connect' test program. Still need to add
pre-spawning of a new child process as soon as an existing one from the pool
has been taking into use. And need to test with the actual JS client.
The zoomed tiles now perfectly match the new ones that are about
to be received from the server.
The zooming factor is again exponentail (1.2) instead of linear.
TODO: when the window size modifies the gets paned out of the bounds
