[RFC wayland-protocols] input-method: Add zwp-input-method-v2
Dorota Czaplejewicz
dorota.czaplejewicz at puri.sm
Thu Oct 4 19:30:55 UTC 2018
Thank you Simon for reading the proposal so carefully!
My replies are inline.
On Fri, 07 Sep 2018 11:54:36 +0000
Simon Ser <contact at emersion.fr> wrote:
> On 6 August 2018 3:00 PM, Dorota Czaplejewicz <dorota.czaplejewicz at puri.sm> wrote:
> > This protocol is based on v1, and current text-input-v3.
> >
> > The pieces passing data relevant to the application on the other side of the
> > compositor are a mirror copy of text-input-v3 events and requests.
> >
> > Compared to input-method-v1:
> > - assumes that once preedit is displayed, no selection can be active, removing
> > some selection handling
> > - follow text-input and removes language indicators
> > - explicitly attaches to seats
> > - removes "commit" text which would replace the preedit string automatically
> > in case it wasn't "confirmed" (whatever it means)
> > - adds double-buffering in the same places as text-input-v3
> > - drops input_method_context and places its functionality directly in
> > input_method
> > - removes the ability to move the cursor position outside of preedit. It still
> > allows to delete a larger chunk of text and replace it with a preedit
> > - doesn't allow for sending of keyboard events to the compositor
> > - Doesn't define any surfaces except for a special compositor-positioned popup
> > ---
> > Hi,
> >
> > the third item on the path to well-supported virtual keyboard experience under
> > Wayland comes from Purism. This one allows the compositor to delegate text
> > input and composition duties to an application instead of handling it itself.
> > Input-method-delegating compositor would typically become only a broker
> > between the input method client and other applications.
> >
> > I took the existing input-method protocol, and after dissecting it with the
> > help of wlroots developers, I came up with an improved version, which is
> > attached for your (re)viewing pleasure.
> >
> > A large part of this protocol was taken from recent text-input-v3, and some
> > description text was improved. Still, the protocol has a couple of rough
> > edges, which is why it's titled RFC and not a patch.
> >
> > The issues I have had most trouble with are related to the handling of
> > keyboard grabs. These are meant to allow traditional, keyboard-based input
> > methods, to take over keyboard input in order to compose text in a different
> > way.
> >
> > First, keyboard grabs are defined as unreliable. I'm not sure whether this is
> > the right choice, but given that making them more reliable seems rather
> > complicated, this is the default one.
> >
> > In addition, handling the keyboard events themselves is troublesome, because
> > an input method, even if it has a surface, is not meant to have keyboard focus
> > while it's in operation. Returning wl_keyboard as new_id seems not to be
> > possible due to versioning. Should the request make an existing wl_keyboard
> > instance change behaviour? Or perhaps there should be a new
> > zwp_input_method_keyboard mimicking the wl_keyboard interface?
> >
> > I'm interested in your opinions.
> >
> > Thank you,
> > Dorota Czaplejewicz
>
> Thansk for your RFC!
>
> > Makefile.am | 1 +
> > unstable/input-method/input-method-unstable-v2.xml | 403 +++++++++++++++++++++
> > 2 files changed, 404 insertions(+)
> > create mode 100644 unstable/input-method/input-method-unstable-v2.xml
> >
> > diff --git a/Makefile.am b/Makefile.am
> > index 6394e26..f3b9f80 100644
> > --- a/Makefile.am
> > +++ b/Makefile.am
> > @@ -7,6 +7,7 @@ unstable_protocols = \
> > unstable/text-input/text-input-unstable-v1.xml \
> > unstable/text-input/text-input-unstable-v3.xml \
> > unstable/input-method/input-method-unstable-v1.xml \
> > + unstable/input-method/input-method-unstable-v2.xml \
> > unstable/xdg-shell/xdg-shell-unstable-v5.xml \
> > unstable/xdg-shell/xdg-shell-unstable-v6.xml \
> > unstable/relative-pointer/relative-pointer-unstable-v1.xml \
> > diff --git a/unstable/input-method/input-method-unstable-v2.xml b/unstable/input-method/input-method-unstable-v2.xml
> > new file mode 100644
> > index 0000000..8cf8e29
> > --- /dev/null
> > +++ b/unstable/input-method/input-method-unstable-v2.xml
> > @@ -0,0 +1,403 @@
> > +<?xml version="1.0" encoding="UTF-8"?>
> > +<protocol name="input_method_unstable_v2">
> > +
> > + <copyright>
> > + Copyright © 2012, 2013 Intel Corporation
> > + Copyright © 2015, 2016 Jan Arne Petersen
> > + Copyright © 2017, 2018 Red Hat, Inc.
> > + Copyright © 2018 Purism SPC
> > +
> > + Permission is hereby granted, free of charge, to any person obtaining a
> > + copy of this software and associated documentation files (the "Software"),
> > + to deal in the Software without restriction, including without limitation
> > + the rights to use, copy, modify, merge, publish, distribute, sublicense,
> > + and/or sell copies of the Software, and to permit persons to whom the
> > + Software is furnished to do so, subject to the following conditions:
> > +
> > + The above copyright notice and this permission notice (including the next
> > + paragraph) shall be included in all copies or substantial portions of the
> > + Software.
> > +
> > + THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> > + IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> > + FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> > + THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> > + LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> > + FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> > + DEALINGS IN THE SOFTWARE.
> > + </copyright>
> > +
> > + <description summary="Protocol for creating input methods">
> > + This protocol allows applications to act as input methods for compositors.
> > +
>
> Nit: there's trailing whitespace here (there are more of these below too).
>
> > + An input method context is used to manage the state of the input method.
> > +
> > + Text strings are UTF-8 encoded, their indices and lengths are in bytes.
> > +
> > + This document adheres to the RFC 2119 when using words like "must",
> > + "should", "may", etc.
> > +
> > + Warning! The protocol described in this file is experimental and
> > + backward incompatible changes may be made. Backward compatible changes
> > + may be added together with the corresponding interface version bump.
> > + Backward incompatible changes are done by bumping the version number in
> > + the protocol and interface names and resetting the interface version.
> > + Once the protocol is to be declared stable, the 'z' prefix and the
> > + version number in the protocol and interface names are removed and the
> > + interface version number is reset.
> > + </description>
> > +
> > + <interface name="zwp_input_method_v2" version="1">
> > + <description summary="input method">
> > + An input method object allows for clients to compose text.
> > +
> > + The objects connects the client to a text input in an application, and
> > + lets the client to serve as an input method for a seat.
> > +
> > + The zwp_input_method_v2 object can occupy two distinct states: active and
> > + inactive. In the active state, the object is associated to and
> > + communicates with a text input. In the inactive state, there is no
> > + associated text input, and the only communication is with the compositor.
> > + Initially, the input method is in the inactive state.
> > +
> > + Requests issued in the inactive state must be accepted by the compositor.
> > + Because of the serial mechanism, and the state reset on activate event,
> > + they will not have any effect on the state of the next text input.
> > +
> > + There must be no more than one input method object per seat.
> > + </description>
> > +
> > + <event name="activate">
> > + <description summary="input method has been requested">
> > + Notification that a text input focused on this seat requested the input
> > + method to be activated.
> > +
> > + This request must be issued every time a text input requests an input
> > + method.
>
> s/request/event/ (also applies to below)
>
> Can a compositor reject a text input request? If so, maybe replacing "must" with
> "will" would soften the requirements.
That sounds fair. I think I snuck in an implementation detail here - some future text input protocol might not need an explicit request. In addition, if the compositor provides its own input method, it may choose that one. Even if not, then rejecting should be done by not sending `text-input.enter` in the first place.
I'll change it to a more neutral sentence:
This event serves the purpose of providing the compositor with an
active input method.
>
> > + This request resets all state associated with previous enable, disable,
> > + set_surrounding_text, set_text_change_cause, set_content_type, and
> > + set_cursor_rectangle requests, as well as the state associated with
> > + preedit_string, commit_string, and delete_surrounding_text events. In
> > + addition, it marks the input method object as active.
> > +
> > + The set_surrounding_text, set_content_type and set_cursor_rectangle
> > + requests must follow before the next done event if the text input
> > + supports the respective functionality.
> > +
> > + State set with this event is double-buffered. It will get applied on
> > + the next zwp_input_method_v2.done event, and stay valid until changed.
> > + </description>
> > + </event>
> > +
> > + <event name="deactivate">
> > + <description summary="deactivate event">
> > + Notification that this seat's current text input requested the input
> > + method to be deactivated.
> > +
> > + This event mrks the zwp_input_method_v2 object as inactive.
> > +
> > + When the seat has the keyboard capability the text-input focus follows
> > + the keyboard focus.
> > +
> > + State set with this event is double-buffered. It will get applied on
> > + the next zwp_input_method_v2.done event, and stay valid until changed.
> > + </description>
> > + </event>
> > +
> > + <event name="surrounding_text">
> > + <description summary="surrounding text event">
> > + Sets the surrounding plain text around the cursor, excluding the
> > + preedit text.
> > +
> > + If any preedit text is present, it is replaced with the cursor for the
> > + purpose of this event.
> > +
> > + The argument text is a buffer containing the preedit string, and must
> > + include the cursor position, and the complete selection. It should
> > + contain additional characters before and after these. There is a
> > + maximum length of wayland messages, so text can not be longer than 4000
> > + bytes.
> > +
> > + cursor is the byte offset of the cursor within the text buffer.
> > +
> > + anchor is the byte offset of the selection anchor within the text
> > + buffer. If there is no selected text, anchor must be the same as
> > + cursor.
> > +
> > + If this request does not arrive before the first done event, the input
> > + method may assume that the text input does not support this
> > + functionality and ignore following surrounding_text events.
> > +
> > + Values set with this event are double-buffered. They will get applied
> > + and set to initial values on the next zwp_input_method_v2.done
> > + event.
> > +
> > + The initial state for affected fields is empty, meaning that the text
> > + input does not support sending surrounding text. If the empty values
> > + get applied, subsequent attempts to change them may have no effect.
> > + </description>
> > + <arg name="text" type="string"/>
> > + <arg name="cursor" type="uint"/>
> > + <arg name="anchor" type="uint"/>
> > + </event>
> > +
> > + <event name="text_change_cause">
> > + <description summary="indicates the cause of surrounding text change">
> > + Tells the input method why the text surrounding the cursor changed.
> > +
> > + Whenever the client detects an external change in text, cursor, or
> > + anchor posision, it must issue this request to the compositor. This
> > + request is intended to give the input method a chance to update the
> > + preedit text in an appropriate way, e.g. by removing it when the user
> > + starts typing with a keyboard.
> > +
> > + cause describes the source of the change.
> > +
> > + The value set with this event is double-buffered. It will get applied
> > + and set to its initial value on the next zwp_input_method_v2.done
> > + event.
> > +
> > + The initial value of cause is input_method.
> > + </description>
> > + <arg name="cause" type="uint" enum="zwp_text_input_v3.change_cause"/>
> > + </event>
> > +
> > + <event name="content_type">
> > + <description summary="content purpose and hint">
> > + Indicates the content type and hint for the current
> > + input_method_context instance.
> > +
> > + Values set with this event are double-buffered. They will get applied
> > + on the next zwp_input_method_v2.done event.
> > +
> > + The initial value for hint is none, and the initial value for purpose
> > + is normal.
> > + </description>
> > + <arg name="hint" type="uint" enum="zwp_text_input_v3.content_hint"/>
> > + <arg name="purpose" type="uint" enum="zwp_text_input_v3.content_purpose"/>
> > + </event>
> > +
> > + <event name="done">
> > + <description summary="apply state">
> > + Atomically applies state changes recently sent to the client.
> > +
> > + The done event establishes and updates the state of the client, and
> > + must be issued after any changes to apply them.
> > +
> > + Text input state (content purpose, content hint, surrounding text, and
> > + change cause) is conceptually double-buffered within an input method
> > + context.
> > +
> > + Events modify the pending state, as opposed to the current state in use
> > + by the input method. A done event atomically applies all pending state,
> > + replacing the current state. After done, the new pending state is as
> > + documented for each related request.
> > +
> > + Events must be applied in the order of arrival.
> > +
> > + Neither current nor pending state are modified unless noted otherwise.
> > + </description>
> > + </event>
> > +
> > + <request name="commit_string">
> > + <description summary="commit string">
> > + Send the commit string text for insertion to the application.
> > +
> > + Inserts a string at current cursor position (see commit event
> > + sequence). The string to commit could be either just a single character
> > + after a key press or the result of some composing.
> > +
> > + The argument text is a buffer containing the string to insert. There is
> > + a maximum length of wayland messages, so text can not be longer than
> > + 4000 bytes.
> > +
> > + Values set with this event are double-buffered. They must be applied
> > + and reset to initial on the next zwp_text_input_v3.done event.
>
> It would probably be better to mention the commit request here, rather than the
> done event.
Oh my, so many typos.
>
> > + The initial value of text is an empty string.
> > + </description>
> > + <arg name="text" type="string"/>
> > + </request>
> > +
> > + <request name="preedit_string">
> > + <description summary="pre-edit string">
> > + Send the pre-edit string text to the application text input.
> > +
> > + Place a new composing text (pre-edit) at the current cursor position.
> > + Any previously set composing text must be removed. Any previously
> > + existing selected text must be removed. The cursor is moved to a new
> > + position within the preedit string.
> > +
> > + The argument text is a buffer containing the preedit string. There is
> > + a maximum length of wayland messages, so text can not be longer than
> > + 4000 bytes.
> > +
> > + The arguments cursor_begin and cursor_end are counted in bytes relative
> > + to the beginning of the submitted string buffer. Cursor should be
> > + hidden by the text input when both are equal to -1.
> > +
> > + cursor_begin indicates the beginning of the cursor. cursor_end
> > + indicates the end of the cursor. It may be equal or different than
> > + cursor_begin.
> > +
> > + Values set with this event are double-buffered. They must be applied on
> > + the next zwp_input_method_v2.commit event.
> > +
> > + The initial value of text is an empty string. The initial value of
> > + cursor_begin, and cursor_end are both 0.
> > + </description>
> > + <arg name="text" type="string"/>
> > + <arg name="cursor_begin" type="int"/>
> > + <arg name="cursor_end" type="int"/>
> > + </request>
> > +
> > + <request name="delete_surrounding_text">
> > + <description summary="delete text">
> > + Remove the surrounding text.
> > +
> > + before_length and after_length are the number of bytes before and after
> > + the current cursor index (excluding the preedit text) to delete.
> > +
> > + If any preedit text is present, it is replaced with the cursor for the
> > + purpose of this event. In effect before_length is counted from the
> > + beginning of preedit text, and after_length from its end (see commit
> > + event sequence).
> > +
> > + Values set with this event are double-buffered. They must be applied
> > + and reset to initial on the next zwp_input_method_v2.commit request.
> > +
> > + The initial values of both before_length and after_length are 0.
> > + </description>
> > + <arg name="before_length" type="uint"/>
> > + <arg name="after_length" type="uint"/>
> > + </request>
> > +
> > + <request name="commit">
> > + <description summary="apply state">
> > + Apply state changes from commit_string, preedit_string and
> > + delete_surrounding_text requests.
> > +
> > + The state relating to these events is double-buffered, and each one
> > + modifies the pending state. This request replaces the current state
> > + with the pending state.
> > +
> > + The connected text input is expected to proceed by evaluating the
> > + changes in the following order:
> > +
> > + 1. Replace existing preedit string with the cursor.
> > + 2. Delete requested surrounding text.
> > + 3. Insert commit string with the cursor at its end.
> > + 4. Calculate surrounding text to send.
> > + 5. Insert new preedit text in cursor position.
> > + 6. Place cursor inside preedit text.
> > +
> > + The serial number reflects the last state of the zwp_input_method_v2
> > + object known to the client. The value of the serial argument must be
> > + equal to the number of commit requests already issued on that object.
> > + When the compositor receives a done event with a serial different than
>
> The compositor sends events, so it won't receive a done event. Is it a text
> input serial?
>
> > + the number of past commit requests, it must proceed as normal, except
> > + it should not change the current state of the zwp_input_method_v2
> > + object.
>
> I'm not sure I understand the purpose of serials here. The compositor can count
> the number of incoming commit requests itself. What happens if the client sends
> an invalid serial?
>
Sorry, that's another messup with directions. This section should look like this:
The serial number reflects the last state of the zwp_input_method_v2
object known to the client. The value of the serial argument must be
equal to the number of done events already issued by that object. When
the compositor receives a commit request with a serial different than
the number of past done events, it must proceed as normal, except it
should not change the current state of the zwp_input_method_v2 object.
> > + </description>
> > + <arg name="serial" type="uint"/>
> > + </request>
> > +
> > + <request name="get_input_popup_surface">
> > + <description summary="create popup surface">
> > + Creates a new zwp_input_popup_surface_v2 object wrapping a given
> > + surface.
> > + </description>
> > + <arg name="id" type="new_id" interface="zwp_input_popup_surface_v2"/>
> > + <arg name="surface" type="object" interface="wl_surface"/>
> > + </request>
> > +
> > + <request name="grab_keyboard">
> > + <description summary="grab hardware keyboard">
> > + Allow an input method to receive hardware keyboard input and process
> > + key events to generate text events (with pre-edit) over the wire. This
> > + allows input methods which compose multiple key events for inputting
> > + text like it is done for CJK languages.
> > +
> > + The compositor should send all keyboard events on the seat to the grab
> > + holder via the returned wl_keyboard object. Nevertheless, the
> > + compositor may decide not to forward any particular event. The
> > + compositor must not further process any event after it has been
> > + forwarded to the grab holder.
> > +
> > + Releasing the resulting wl_keyboard object releases the grab.
> > + </description>
> > + <arg name="keyboard" type="new_id" interface="wl_keyboard"/>
>
> So noted above, this is not possible due to interface versioning. I'm not sure
> it's possible to use an existing keyboard instead, because keyboard focus is
> generally bound to a surface (see the enter/leave events).
>
> What are the requirements here? Do we need to send a keymap? If most of
> wl_keyboard is irrelevant here, it would probably be better to add a new
> interface.
The input method indeed needs to receive a keymap, and do generic keyboard things. Looking at wl_keyboard, I think the following apply:
- keymap
- key
- modifiers
- release is not unwelcome
- probably also repeat_info
All in all, I guess these can be simply copied.
>
> > + </request>
> > +
> > + <event name="unavailable">
> > + <description summray="input method unavailable">
> > + The input method ceased to be available.
> > +
> > + The compositor must issue this event as the only event on the object if
> > + there was another input_method object associated with the same seat at
> > + the time of its creation.
> > +
> > + The compositor must issue this request when the object is no longer
> > + useable, e.g. due to seat removal.
> > +
> > + The input method context becomes inert and should be destroyed after
> > + deactivation is handled. Any further requests and events except for the
> > + destroy request must be ignored.
> > + </description>
> > + </event>
> > +
> > + <request name="destroy" type="destructor"/>
>
> This should include details about what happens to objects created via this
> interface.
>
New version:
Destroys the zwp_text_input_v2 object and any associated child
objects, i.e. zwp_input_method_popup_surface_v2 and
zwp_input_method_keyboard_grab_v2.
> > + </interface>
> > +
> > + <interface name="zwp_input_popup_surface_v2" version="1">
> > + <description summary="popup surface">
> > + This surface is a popup for interacting with an input method.
>
> Does this give a role to the wl_surface? (To prevent it from being used for
> another purpose)
Yes, good point. I added this to get_input_popup_surface:
The surface gets assigned the "input_popup" role. If the surface
already has an assigned role, the compositor must issue a protocol
error.
>
> > + The compositor should place it near the active text input area.
>
> What happens if the wl_surface is destroyed before this object? Is it allowed?
I don't think is should be allowed:
The client must not destroy the underlying wl_surface while the
zwp_input_popup_surface_v2 object exists.
>
> > + </description>
> > +
> > + <event name="text_input_rectangle">
> > + <description summary="set text input area position">
> > + Notify about the position of the area of the text input expressed as a
> > + rectangle in surface local coordinates.
> > +
> > + This is a hint to the input method telling it the relative position of
> > + the text being entered.
> > + </description>
> > + <arg name="x" type="int"/>
> > + <arg name="y" type="int"/>
> > + <arg name="width" type="int"/>
> > + <arg name="height" type="int"/>
> > + </event>
> > +
> > + <request name="destroy" type="destructor"/>
> > + </interface>
> > +
> > + <interface name="zwp_input_method_manager_v2" version="1">
> > + <description summary="input method manager">
> > + The input method manager allows the client to become the input method on
> > + a chosen seat.
> > +
> > + No more than one input method must be associated with any seat at any
> > + given time.
> > + </description>
> > +
> > + <request name="get_input_method">
> > + <description summary="request an input method object">
> > + Request a new input zwp_input_method_v2 object associated with a given
> > + seat.
> > + </description>
> > + <arg name="seat" type="object" interface="wl_seat"/>
> > + <arg name="input_method" type="new_id" interface="zwp_input_method_v2"/>
> > + </request>
> > +
> > + <request name="destroy" type="destructor">
> > + <description summary="destroy the input method manager">
> > + Destroys the zwp_input_method_manager_v2 object.
> > +
> > + The zwp_input_method_v2 objects originating from it remain valid.
> > + </description>
> > + </request>
> > + </interface>
> > +</protocol>
> > --
> > 2.14.4
> >
> > _______________________________________________
> > wayland-devel mailing list
> > wayland-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/wayland-devel
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