nanogui: Thread: Window management

Before releasing the official Nano-X-0.5, I want to put in a basic
implementation of a window management API, so that people can start
writing some real window managers before the 0.6 release. The API is going
to take quite a bit of design work to get right, and I'd like to try doing
it on this list. I've never worked on window managers at a low level
before, so I'm pretty much flying blind here.

To start off, here are a few notes I've come up with:

The window manager should be always be linked into the server.

It should be possible to compile the server with no window manager.

The window manager should have a wm_initialise() function, which returns a
structure of pointers to callback functions (or NULL if that function
isn't implemented). Here's a preliminary list of these functions:

	wm_window_create()
  Called with a pointer to a newly created window structure. The window
manager is allowed to do things like creating a new, larger, window to
contain it, along with a menu bar and iconisation, close, maximise, etc.
buttons (we should probably add a new argument to GrNewInputWindow()
which specifies whether the window should be resizable or not though,
along with a RESIZE event. There should also be a window name argument
and a GrRenameWindow() function for setting the name of the window for
the top bar. There should also be "always_on_top" and "sticky" arguments).

	wm_window_destroy()
  Called with a pointer to a window to be destroyed, so the wm can destroy
the parent window it created at the same time.

	wm_window_enter(), wm_window_leave()
  Called with a pointer to a window structure whenever the mouse enters a
window. Used for controlling focus and depth of window.

	wm_window_event()
  Called with an event structure whenever an event needs to be delivered
to a window belonging to the client with the special number belonging to
the window manager. Used for redrawing the border, changing the mouse
pointer when over the resize bars, sending resize events when the borders
are dragged, moving the window if the top bar is dragged, closing,
iconising, maximising, etc. if one of the buttons is clicked.

	wm_keyup(), wm_keydown()
  Called with a pointer to a keyboard event, whenever a keypress is
detected. Should return NULL to let the event be processed and delivered,
or non null if the event should be thrown away. This can be used for
screen locking and hotkey processing.

	wm_mouseup(), wm_mousedown()
  Called with a pointer to a mouse event. Returns NULL to let the event be
processed and delivered or non null if the event should be thrown away.
Also used for screen locking. There's probably no point trapping mouse
movement events though.

	wm_idle()
  Called a fixed number of times a second (10? 30?) in order for the WM to
do any asynchronous processing it needs to do.

In addition, we will need to add functions to Nano-X which the WM can call
to:
	Move a window.
	Bring a window to the top.
	Ask a client to shut down.
	Attempt to forcibly kill a client.
	Set a background image.
	Find out how many virtual desktops there are.
	Switch to a different virtual desktop. (okay, we don't have
virtual desktops, but it should be easy to implement, whilst still being
possible to compile a version which only has one desktop and no code to
handle multiple desktops).

This is nowhere near complete, but I'd like comments on what is already
there, and what I have missed.

--------------- Linux- the choice of a GNU generation. --------------
: Alex Holden (M1CJD)- Caver, Programmer, Land Rover nut, Radio Ham :
-------------------- http://www.linuxhacker.org/ --------------------