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<div class="moz-cite-prefix">Le 24/09/2014 16:41, Jason Ekstrand a
écrit :<br>
</div>
<blockquote
cite="mid:CAOFGe96wAtUKuUMz6YF4i=dNydp5=XyNxdqvVCqMceHtTLo3vA@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">On Wed, Sep 24, 2014 at 1:46 AM,
Matthieu Gautier <span dir="ltr"><<a
moz-do-not-send="true" href="mailto:dev@mgautier.fr"
target="_blank">dev@mgautier.fr</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div>Hi Jason,<br>
<br>
Well, I'll try to be more concise.<br>
<br>
In fact, there are two unrelated parts in my
proposition :<br>
<br>
# First part : getting relative events<br>
<br>
Passing through a wl_pointer that may not exists to
get relative events seems a bit odd to me.<br>
<br>
My main idea is to have a new object (I've call
wl_relative) *not related* to wl_pointer that send to
client the relative events.<br>
If a client want relative events, it open this object
and receive events from it. Simply.<br>
No need to look the wl_pointer or anything else.<br>
<br>
The wl_pointer still continue to work as usual. There
is strictly no change in that part.<br>
<br>
The only relation we may find between wl_relative and
wl_pointer is that relative events are sent only when
the wl_surface as the focus.<br>
In a first approximation, we can say that the
wl_relative focus is the same of wl_pointer focus and
that relative events are send only when
wl_pointer.motion are send (ie, between
wl_pointer.enter and wl_pointer.leave)<br>
But a special compositor could follow its own rules.<br>
</div>
</div>
</blockquote>
<div> <br>
</div>
<div>What is a relative input device? How does the client
know if/how it's related to the wl_pointer?<br>
<br>
The first question is the hard one. A pointer is a
relatively well-dfined thing. We've had mice for ~30
years now and everyone knows what to expect from one.
They give you motion (sort-of relative), they have buttons
(at least one, but usually at least 3), they frequently
have at least one axis of relative motion that we call
"scroll". A mouse is a well-defined input device and we
know what to do with one. We also know that, classically,
they move this little cursor around on the screen in a way
that's defined by the window system and is usually in
absolute coordinates as far as applications are concerned.<br>
<br>
</div>
<div>What is a relative input device? It gives relative
motion. How many axes does it have? How should each axis
be interpreted by applications? What kind of
pseudo-physical model should we use to understand it. (a
mouse cursor "moves" on the screen). Does it have
buttons? How many? What do they do? In order for the
protocol to be useful for applications, all of those
questions need well-defined answers. If it's just "gives
relative events" then we're right back to the horrific
"remap your joystick for every game" problem we had in the
'90s only now you have to remap your mouse too. In fact,
one of the things about mice that's great for game devs is
precisely that they always know what they're getting.<br>
<br>
</div>
<div>Along those lines, there was a protocol proposed for
gamepads some time ago. (you could go dig it up on the
list and read about it). The basic idea there was that
most gamepad designs have more-or-less coalesced into the
XBox/PS form-factor of two sticks, a d-pad, 4 buttons, 2
or 4 triggers, and a "start" buton. You can go online and
find dozens of different companies shipping gamepads that
all have this same basic layout. The idea was to then
create a protocol based on that layout so that game
developers could have a common base to build on. The
reason I bring this up is that the entire reason why the
protocol was feasible at all is that the concept of a
gamepad has become reasonably well-defined to the point
where you could write a common protocol that works for
most combinations of game and gamepad.<br>
</div>
</div>
</div>
</div>
</blockquote>
<br>
I have to agree with you. Trying to write the xml corresponding to
my idea point out this problem.<br>
<br>
Not cause of the definition of the wl_relative (I planned to just
have motion events) but cause without buttons wl_relative is mostly
useless without wl_pointer.<br>
And it doesn't fulfill the constraint for system with a relative
device but without a pointer interpretation of this device.<br>
<br>
However, split the problem in two parts is still relevant for me. We
don't need a lock on the pointer to get the relative movement of the
mouse.<br>
<br>
Why not just add new arguments to the wl_pointer.motion event and
drop the idea of a wl_relative object ? [*]<br>
Those new arguments (delta_x and delta_y) corresponding to the
untransformed relative movement.<br>
<br>
The pointer lock part being unchanged.<br>
<br>
If for any reason the user move the mouse and the pointer position
doesn't change (cause of pointer lock or pointer is already on a
screen corner), <br>
a motion event is still generated but with surface_x/surface_y being
the same as the previous ones.<br>
<br>
[*] I'm not totally aware of what is the general consensus on how to
extend wayland protocol.<br>
Maybe we try to avoid change in the core protocol and want to make
change through extension. In this case, indeed, we cannot just add
arguments to the motion event.<br>
<br>
<blockquote
cite="mid:CAOFGe96wAtUKuUMz6YF4i=dNydp5=XyNxdqvVCqMceHtTLo3vA@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">
<div><br>
As a small note, a classic mouse isn't really relative
because the position on screen sort-of corresponds to the
position on the mouse pad. Sure, it's sloppy and subject
to acceleration, but it's not truly relative like a
trackball. Not that this really matters, but it's worth
pointing out.<br>
</div>
</div>
</div>
</div>
</blockquote>
I'm still thinking that tho pointer stuff is artificial construction
based on relative events. This construction is of course extremely
useful and well integrated by user.<br>
One can imagine a UI without pointer and with relative motion (FPS
game is a example, they use relative events but don't have a notion
of pointer)<br>
<br>
But, I think this point is no more relevant in this discussion.
Having wayland supports this kind of future potential interface
would probably need to many change for a usage that may not worth
it.<br>
<br>
<blockquote
cite="mid:CAOFGe96wAtUKuUMz6YF4i=dNydp5=XyNxdqvVCqMceHtTLo3vA@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
<div> # Second part : pointer lock<br>
<br>
The pointer lock should not be related to relative
events. This is two different parts.<br>
<br>
To acquire a pointer lock, a client just ask it.<br>
It can be by the request
wl_pointer.get_lock(lock_type) (I've called it
set_mode in my past mail but get_lock is a better
name)<br>
<br>
This request return a wl_callback used by the
compositor to end the lock (either cause it refuse it
or the lock normally ends)<br>
The lock can be released by the client using
wl_pointer.release_lock() (former reset_mode)<br>
<br>
The lock_type can be :<br>
- lock : Do not move the pointer (What was in the
Jonas' proposal)<br>
- confine : Confine the pointer into the surface.<br>
<br>
During a lock, all events are still send as usual :<br>
- Relative events from wl_relative are not impacted by
the wl_pointer lock<br>
- wl_pointer.motion are still send in confine mode<br>
- wl_pointer button, axis events are still sent<br>
<br>
# Remarks and QA:<br>
<br>
The main difference compared to Jonas' proposal is
that I totally separate the relative events problem
from the pointer lock problem. (I maybe should have
start by this :) )<br>
In Jonas' proposal you have to acquire the pointer
lock to get relative events. In my proposition we can
get one without having the other.<br>
<br>
I don't especially care if this is my proposal or
Jonas' ones that is kept. But separate the two part in
unrelated problems seems better to me.<br>
<br>
I've you give me times, I will send you a patch of
wayland.xml to describe more precisely what I'm
thinking about.<br>
It could be interesting that Jonas update its protocol
xml with remarks from others to be sure that we
compare up to date proposal and not miss anything.<br>
<br>
- Why not let the application open the device ? <br>
=> For security reasons. We probably don't want
that any applications can open input devices and read
from them all events.<br>
=> Scalability. Devices are not always mouses.
Applications may not know how to read them.<br>
In my past job, I've made a
android application that connect to the STB in Wifi
and discuss directly with the compositor to send input
events. There was no device to read from except a
socket.<br>
- What my proposal can do that Jonas' one can't do ?<br>
=> The only thing I can find is the case where a
seat doesn't have a wl_pointer but have relative
events. For all the rest, Jonas' proposal seems to
work.<br>
=> My proposition seems simpler to me. Less
dependencies between elements, less questions about
who create and release objects. (But It's maybe also
cause it's mine :) )<br>
<br>
Regards,<br>
Matthieu.<br>
<br>
Le 23/09/2014 23:42, Jason Ekstrand a écrit :<br>
</div>
<span class="">
<blockquote type="cite">
<div dir="ltr">
<div>Hi Matthieu,<br>
</div>
Could you please provide more explanation on what
use-cases you are considering and why the current
proposal fails to accomplish them? All I was able
to get from your post was the example of a TV
remote. It's all well and good to completely
disagree with the proposed approach, but without a
good reason as to why it doesn't work, it's kind
of moot.<br>
<div class="gmail_extra"><br>
</div>
<div class="gmail_extra">It's also worth noting
the scope of the proposal. The primary
objective here is to provide a mechanism to take
a device that could be providing relative events
but which the compositor has turned into a
pointer and get the relative events out of it.
It's not intended to be a generic system for
getting relative events.<br>
</div>
<div class="gmail_extra"><br>
</div>
<div class="gmail_extra">On that note, if you want
to get a generic relative motion events, can't
you just open the device and read them? Sure we
could cobble together a specification for how to
read a bunch of buttons and relative events and
then create a cursor from them. I'm pretty sure
it exists in the form of the USB HID spec. How
does reimplementing that in Wayland help us?
There was, at one point, a proposal for
gamepads, but nothing has happened there in a
while.<br>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Tue, Sep 23, 2014 at
9:01 AM, Matthieu Gautier <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:dev@mgautier.fr"
target="_blank">dev@mgautier.fr</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex">Hello,<br>
<br>
I'm pretty new into wayland and the
discussion is relatively long, so I may have
missed arguments/constraints.<br>
However I would like to share my point of
view.<br>
<br>
It seems to me that we are taking the
problem the wrong way.<br>
Relative motions exist as soon as there is a
device generating them. wl_pointer is just a
particular interpretation of those events.<br>
<br>
In fact, we may have a system where we have
relative motion events but no wl_pointer.
Think about a smart tv with a remote control
with accelerator/gyroscope detectors.<br>
This remote may behave as a mouse,
generating relative motion events. But the
main interface of the TV may have no
pointer. The interface should been a set of
icons and user move between them with the
remote buttons.<br>
</blockquote>
<div><br>
</div>
<div>If you're just pressing buttons to move
between icons, then "pointer" is probably
the wrong way to look at it anyway. It's
more "arrow keys" than a pointer.<br>
</div>
</div>
</div>
</div>
</blockquote>
</span> Exactly, there is no pointer in this example.
But there are relative events applications may want to
have.
<div>
<div class="h5"><br>
<blockquote type="cite">
<div dir="ltr">
<div class="gmail_extra">
<div class="gmail_quote">
<div> </div>
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex"> In the same
way, we may want that special applications
still have access to motion events:<br>
- A web browser that will display itself
the pointer (or activate wl_pointer in the
compositor)<br>
- A video game<br>
- Any application that want make gesture
recognition.<br>
<br>
In this context, wl_pointer is a special
use-case of a shell and having a mouse
device doesn't imply having a pointer.<br>
<br>
Relative motions should be always
available (if there is a device) and
wl_pointer should be created on top of
relative motions.<br>
Trying to reduce the wl_pointer behavior
to have the raw events seems to me the
contrary of what we have to do.<br>
<br>
<br>
What I propose is :<br>
<br>
- Having a way to get "relative input
object" (lets call it wl_relative for now)
from wl_seat.<br>
- Having a way to get a wl_pointer from
the wl_seat at it is already the case.<br>
<br>
Relative events a sent to client if it is
active (It is to the compositor to decide
this, as usual) whatever there is a
wl_pointer or not.<br>
<br>
The pointer lock interface will become
some kind of "deactivate/configure
wl_pointer".<br>
<br>
# Functionally :<br>
<br>
A combination of :<br>
- Hide the cursor (already available with
wl_pointer.set_cursor)<br>
- Don't not update wl_pointer position
from relative events.<br>
- Confine the pointer position into my
wl_surface.<br>
- Set wl_pointer at this position.<br>
<br>
- A fps game will hide the cursor and
deactivate update of wl_pointer position.<br>
- A strategy game will just confine the
pointer.<br>
- A application with a 3D view that what
to rotate it when user drag the mouse will
just deactivate update of pointer position
between button_down and button_up.<br>
- A application that just want relative
motion events do nothing.<br>
<br>
At any time, relative motion events are
sent to client through the wl_relative
object. Regardless of the state of
wl_pointer.<br>
It is up to the client to handle events
from wl_pointer or wl_relative depending
of which kind of information it wants.<br>
<br>
<br>
# Interface :<br>
<br>
The wl_pointer could gain two (four?) more
requests :<br>
<br>
- set_mode(mode, callback)<br>
- reset_mode()<br>
( - has_mode<br>
- get_mode )<br>
<br>
The default mode is the mode we have for
now (no special constraints)<br>
A client can change the mode of a
wl_pointer. It gets a callback.<br>
When compositor stops the special mode (or
refuse it) the done event of the callback
is sent.<br>
When the client has finished with special
mode, it sends the reset_mode request.<br>
<br>
The wl_pointer.leave event may or not be
sent to client when the done event is sent
(The pointer may still being inside the
wl_surface when special mode ends)<br>
However a wl_pointer.leave event implies a
done event. (We cannot have a special mode
if we don't have the pointer focus)<br>
<br>
<br>
On the interface to get the wl_relative
object from seat, it depends :<br>
<br>
Is there a possibility to have several
cursor on one seat ?</blockquote>
<div><br>
</div>
<div>One cursor per seat. If there are
multiple physical mice, then you get an
aggregate of all the mice. You can,
however, have multiple seats in which case
you will get multiple pointers.<br>
</div>
<div> </div>
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex"> (Two mouses
moving two cursors)<br>
Does wl_seat.get_cursor return always a
proxy to the same object ?<br>
</blockquote>
<div><br>
</div>
<div>Yes, all pointers created from the same
seat are identical.<br>
</div>
<div> </div>
<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px
#ccc solid;padding-left:1ex"> <br>
- If there is only one cursor, we can
simply add a get_relative request to
wl_seat.<br>
- If not, we should get a object from the
other.<br>
. Ideally, get the wl_pointer from
wl_relative. (and wl_relative from
wl_seat)<br>
. Practically, cause of the existent,
get wl_relative from wl_pointer.<br>
<br>
<br>
Regards,<br>
Matthieu Gautier.
<div>
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