Clicking the button generates a WindowCloseRequest event which the client app
then has to deal with. The default behavior for GWindow is to close() itself.
I also added a flag, GWindow::should_exit_event_loop_on_close() which does
what it sounds like it does.
This patch exposed some bugs in GWindow and GWidget teardown.
This ownership model is a bit confusing. There's a retain cycle between
MasterPTY and SlavePTY, but it's broken when the SlavePTY is closed, meaning
that there are no more FileDescriptors referring to it.
This required a fair bit of plumbing. The CharacterDevice::close() virtual
will now be closed by ~FileDescriptor(), allowing device implementations to
do custom cleanup at that point.
One big problem remains: if the master PTY is closed before the slave PTY,
we go into crashy land.
Instead of clients painting whenever they feel like it, we now ask that they
paint in response to a paint message.
After finishing painting, clients notify the WindowServer about the rect(s)
they painted into and then flush eventually happens, etc.
This stuff leaves us with a lot of badly named things. Need to fix that.
When you open /dev/ptmx, you get a file descriptor pointing to one of the
available MasterPTY's. If none are available, you get an EBUSY.
This makes it possible to open multiple (up to 4) Terminals. :^)
To support this, I also added a CharacterDevice::open() that gets control
when VFS is opening a CharacterDevice. This is useful when we want to return
a custom FileDescriptor like we do here.
