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Core wayland protocol
- surface.set_grab_mode(GRAB_OWNER_EVENTS vs GRAB_SURFACE_EVENTS), to
make menus work right: click and drag in a menubar grabs the
pointer to the menubar (which we need for detecting motion into
another menu item), but we need events for the popup menu surface
as well.
- The message format has to include information about number of fds
in the message so we can skip a message correctly. Or we should
just give up on trying to recover from unknown messages. We need
to make sure you never get a message from an interface you don't
know about (using per-client id space and subscribe) or include
information on number of fds, so marshalling logic can skip.
- generate pointer_focus (and drag focus) on raise/lower, move
windows, all kinds of changes in surface stacking.
- glyph cache
buffer = drm.create_buffer(); /* buffer with stuff in it */
cache.upload(buffer, x, y, width, height, int hash)
drm.buffer: id, name, stride etc /* event to announce cache buffer */
cache.image: hash, buffer, x, y, stride /* event to announce
* location in cache */
cache.reject: hash /* no upload for you! */
cache.retire: buffer /* cache has stopped using buffer, please
* reupload whatever you had in that buffer */
- DnD issues:
Root window must send NULL type (to decline drop) or
x-wayland/root-something type if the source offers that. But the
target deletes the drag_offer object when drag.pointer_focus leaves
the surface...
How do we animate the drag icon back to the drag origin in case of
a failed drag?
How to handle surfaces from clients that don't know about dnd or
don't care? Maybe the dnd object should have a
dnd.register_surface() method so clients can opt-in the surfaces
that will participate in dnd. Or just assume client is not
participating until we receive an accept request.
- Selection/copy+paste issues: is it sufficient to only introduce the
selection offer when a client receives kb focus? Or maybe it is
actually a security feature? Clipboard manager in server for
retained selections?
- Pointer image issue:
- A direct touch input device (eg touch screen) doesn't have a
pointer; indicate that somehow.
- Cursor themes, tie in with glyph/image cache.
- Discard buffer, as in "wayland discarded your buffer, it's no
longer visible, you can stop updating it now.", reattach, as in "oh
hey, I'm about to show your buffer that I threw away, what was it
again?". for wayland system compositor vt switcing, for example,
to be able to throw away the surfaces in the session we're
switching away from. for minimized windows that we don't want live
thumb nails for. etc.
- Initial placement of surfaces. Guess we can do, 1)
surface-relative (menus), 2) pointer-relative (tooltips and
right-click menus) or 3) server-decides (all other top-levels).
- Per client id space. Each client has an entire 32 bit id namespace
to itself. On the server side, each struct wl_client has an object
hash table. Object announcements use a server id space and clients
must respond with subscribe request with a client id for the
object. Part of wl_proxy_create_for_id():
wl_display_subscribe(display, id, new_id, my_version);
or maybe
wl_display_bind(display, id, new_id, my_version);
Fixes a few things:
- Maps the global object into the client id space, lets client
allocate the id. All ids are allocated by the client this way,
which fixes the range protocol problem.
- Tells the server that the client is interested in events from
the object. Lets the server know that a client participates in a
certain protocol (like drag and drop), so the server can account
for whether or not the client is expected to reply
- Server emits initial object state event(s) in reponse to
receiving the subscribe request. Introduces an extra round trip
at initialization time, but the server will still announces all
objects in one burst and the client can subscribe in a burst as
well.
- Separates client resources, since each client will have it's own
hash table. It's not longer possible to guess the id of another
surface and access it.
- Server must track the client id for each client an object is
exposed to. In some cases we know this (a surface is always
only owned by one client), in other cases it provides a way to
track who's interested in the object events. For input device
events, we can look up the client name when it receives pointer
focus or keyboard focus and cache it in the device.
- Server must know which id to send when passing object references
in events. We could say that any object we're passing to a
client must have a server id, and each client has a server id ->
client id hash.
- When a surface is the size of the screen and on top, we can set the
scanout buffer to that surface directly. Like compiz unredirect
top-level window feature. Except it won't have any protocol state
side-effects and the client that owns the surface won't know. We
lose control of updates. Should work well for X server root window
under wayland. Should be possible for yuv overlays as well.
- what about cursors then? maybe use hw cursors if the cursor
satisfies hw limitations (64x64, only one cursor), switch to
composited cursors if not.
- clients needs to allocate the surface to be suitable for
scanout, which they can do whenever they go fullscreen.
- multihead, screen geometry and crtc layout protocol, hotplug, lcd
subpixel info
- a wayland settings protocol to tell clients about themes (icons,
cursors, widget themes), fonts details (family, hinting
preferences) etc. Just send all settings at connect time, send
updates when a setting change. Getting a little close to gconf
here, but could be pretty simple:
interface "settings":
event int_value(string name, int value)
event string_value(string name, string value)
but maybe it's better to just require that clients get that from
somewhere else (gconf/dbus).
- input device discovery, hotplug
- Advertise axes as part of the discovery, use something like
"org.wayland.input.x" to identify the axes.
- keyboard state, layout events at connect time and when it
changes, keyboard leds
- relative events
- multi touch?
- synaptics, 3-button emulation, scim
- drm bo access control, authentication, flink_to
- Range protocol may not be sufficient... if a server cycles through
2^32 object IDs we don't have a way to handle wrapping. And since
we hand out a range of 256 IDs to each new clients, we're just
talking about 2^24 clients. That's 31 years with a new client
every minute... Maybe just use bigger ranges, then it's feasible
to track and garbage collect them when a client dies.
- Add protocol to let applications specify the effective/logical
surface rectangle, that is, the edge of the window, ignoring drop
shadows and other padding. The compositor needs this for snapping
and constraining window motion. Also, maybe communicate the opaque
region of the window (or just a conservative, simple estimate), to
let the compositor reduce overdraw.
- multi gpu, needs queue and seqno to wait on in requests
Clients and ports
- port gtk+
- draw window decorations in gtkwindow.c
- Details about pointer grabs. wayland doesn't have active grabs,
menus will behave subtly different. Under X, clicking a menu
open grabs the pointer and clicking outside the window pops down
the menu and swallows the click. without active grabs we can't
swallow the click. I'm sure there much more...
- Port Qt? There's already talk about this on the list.
- X on Wayland
- move most of the code from xf86-video-intel into a Xorg wayland
module.
- don't ask KMS for available output and modes, use the info from
the wayland server. then stop mooching off of drmmode.c.
- map multiple wayland input devices to MPX in Xorg.
- rootless; avoid allocating and setting the front buffer, draw
window decorations in the X server (!), how to map input?
- gnome-shell as a wayland session compositor
- runs as a client of the wayland session compositor, uses
clutter+egl on wayland
- talks to an Xorg server as the compositing and window manager
for that server and renders the output to a wayland surface.
the Xorg server should be modified to take input from the system
compositor through gnome-shell, but not allocate a front buffer.
- make gnome-shell itself a nested wayland server and allow native
wayland clients to connect and can native wayland windows with
the windows from the X server.
- qemu as a wayland client; session surface as X case
- qemu has too simple acceleration, so a Wayland backend like the
SDL/VNC ones it has now is trivial.
- paravirt: forward wayland screen info as mmio, expose gem ioctls as mmio
- mapping vmem is tricky, should try to only use ioctl (pwrite+pread)
- not useful for Windows without a windows paravirt driver.
- two approaches: 1) do a toplevel qemu window, or 2) expose a
wayland server in the guest that forwards to the host wayland
server, ie a "remote" compositor, but with the gem buffers
shared. could do a wl_connection directly on mmio memory, with
head and tail pointers. use an alloc_head register to indicate
desired data to write, if it overwrites tail, block guest. just
a socket would be easier.
- moblin as a wayland compositor
- clutter as a wayland compositors
- argh, mutter
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