[PATCH v8 wayland-protocols] text-input: Add v3 of the text-input protocol

Dorota Czaplejewicz dorota.czaplejewicz at puri.sm
Sat Jul 28 18:17:56 UTC 2018

From: Carlos Garnacho <carlosg at gnome.org>

This new protocol description is an evolution of v2.

- All pre-edit text styling is gone.
- Pre-edit cursor can span characters.
- No events regarding input panel (OSK) state nor covered rectangle.
  Compositors are still free to handle situations where the keyboard
  focus rectangle is covered by the input panel.
- No set_preferred_language request for clients.
- There is no event to send keysyms. Compositors can use wl_keyboard
  interface instead.
- All state is double-buffered, with specified defaults.
- The compositor can be notified about external changes to the state.
- The client can detect outdated requests.

Signed-off-by: Dorota Czaplejewicz <dorota.czaplejewicz at puri.sm>
Signed-off-by: Carlos Garnacho <carlosg at gnome.org>
Hello all,

this new change stems from real experiences developing an implementation of text-input. Under Carlos' guidance, I've been developing support in GTK3, as well as wlroots [0]. There were lessons to be learned, and they are incorporated into this new patch revision.

The one significant change consists of adding a serial number to each state sent by the client. The input method (e.g. the compositor) will then update its beliefs about the text field state, and send new requests, along with the serial number. This allows the client to detect requests based on outdated states and handle them in a special way, i.e. ignore requests for permanent changes.

At the same time, the enable request becomes effective only after a commit, to allow the client to send a state bundle together with it.

The second important change regards passing set_surrounding_text metadata in the set_text_change_cause request. It's necessary for the input method to understand when the user stopped using it to back off. The change_cause enumeration could be extended in the future with causes such as "navigation", "typing", or "redaction" to achieve better granularity than a catchall "other".

Apart from these changes, some descriptions have been clarified, and circumstances were under which set_surrounding_text should be sent were spelled out.

I hope that you enjoy the read!

Dorota Czaplejewicz

[0] https://gitlab.gnome.org/GNOME/gtk/merge_requests/272

 Makefile.am                                    |   1 +
 unstable/text-input/text-input-unstable-v3.xml | 441 +++++++++++++++++++++++++
 2 files changed, 442 insertions(+)
 create mode 100644 unstable/text-input/text-input-unstable-v3.xml

diff --git a/Makefile.am b/Makefile.am
index 4b9a901..86d7ca9 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -3,6 +3,7 @@ unstable_protocols =								\
 	unstable/fullscreen-shell/fullscreen-shell-unstable-v1.xml		\
 	unstable/linux-dmabuf/linux-dmabuf-unstable-v1.xml			\
 	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/xdg-shell/xdg-shell-unstable-v5.xml				\
 	unstable/xdg-shell/xdg-shell-unstable-v6.xml				\
diff --git a/unstable/text-input/text-input-unstable-v3.xml b/unstable/text-input/text-input-unstable-v3.xml
new file mode 100644
index 0000000..2e8b72f
--- /dev/null
+++ b/unstable/text-input/text-input-unstable-v3.xml
@@ -0,0 +1,441 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="text_input_unstable_v3">
+  <copyright>
+    Copyright © 2012, 2013 Intel Corporation
+    Copyright © 2015, 2016 Jan Arne Petersen
+    Copyright © 2017, 2018 Red Hat, Inc.
+    Copyright © 2018       Purism SPC
+    Permission to use, copy, modify, distribute, and sell this
+    software and its documentation for any purpose is hereby granted
+    without fee, provided that the above copyright notice appear in
+    all copies and that both that copyright notice and this permission
+    notice appear in supporting documentation, and that the name of
+    the copyright holders not be used in advertising or publicity
+    pertaining to distribution of the software without specific,
+    written prior permission.  The copyright holders make no
+    representations about the suitability of this software for any
+    purpose.  It is provided "as is" without express or implied
+    warranty.
+  </copyright>
+  <interface name="zwp_text_input_v3" version="1">
+    <description summary="text input">
+      The zwp_text_input_v3 interface represents text input and input methods
+      associated with a seat. It provides enter/leave events to follow the
+      text input focus for a seat.
+      Requests are used to enable/disable the text-input object and set
+      state information like surrounding and selected text or the content type.
+      The information about the entered text is sent to the text-input object
+      via the preedit_string and commit_string events.
+      Text is valid UTF-8 encoded, indices and lengths are in bytes. Indices
+      must not point to middle bytes inside a code point: they must either
+      point to the first byte of a code point or to the end of the buffer.
+      Lengths must be measured between two valid indices.
+      Focus moving throughout surfaces will result in the emission of
+      zwp_text_input_v3.enter and zwp_text_input_v3.leave events. The focused
+      surface must perform zwp_text_input_v3.enable and
+      zwp_text_input_v3.disable requests as the keyboard focus moves across
+      editable and non-editable elements of the UI. Those two requests are not
+      expected to be paired with each other, the compositor must be able to
+      handle consecutive series of the same request.
+      State is sent by the state requests (set_surrounding_text,
+      set_content_type and set_cursor_rectangle) and a commit request. After an
+      enter event or disable request all state information is invalidated and
+      needs to be resent by the client.
+      This protocol defines requests and events necessary for regular clients
+      to communicate with an input method. The zwp_input_method protocol
+      defines the interfaces necessary to implement standalone input methods.
+      If a compositor implements both interfaces, it will be the arbiter of the
+      communication between both.
+      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>
+    <request name="destroy" type="destructor">
+      <description summary="Destroy the wp_text_input">
+        Destroy the wp_text_input object. Also disables all surfaces enabled
+        through this wp_text_input object.
+      </description>
+    </request>
+    <request name="enable">
+      <description summary="Request text input to be enabled">
+        Requests text input on the surface previously obtained from the enter
+        event.
+        This request must be issued every time the active text input changes
+        to a new one, including within the current surface. Use
+        zwp_text_input_v3.disable when there is no longer any input focus on
+        the current surface.
+        This request resets all state associated with previous enable,
+        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.
+        The set_surrounding_text, set_content_type and set_cursor_rectangle
+        requests must follow if the text input supports the necessary
+        functionality.
+        State set with this request is double-buffered. It will get applied on
+        the next zwp_text_input_v3.commit request, and stay valid until the
+        next enable or disable request.
+        The changes must be applied by the compositor after issuing a
+        zwp_text_input_v3.commit request.
+      </description>
+    </request>
+    <request name="disable">
+      <description summary="Disable text input on a surface">
+        Explicitly disable text input on the current surface (typically when
+        there is no focus on any text entry inside the surface).
+      </description>
+    </request>
+    <request name="set_surrounding_text">
+      <description summary="sets the surrounding text">
+        Sets the surrounding plain text around the input, excluding the preedit
+        text.
+        The client should notify the compositor of any changes in any of the
+        values carried with this request, including changes caused by handling
+        incoming text-input events as well as changes caused by other
+        mechanisms like keyboard typing.
+        If the client is unaware of the text around the cursor, it should not
+        issue this request, to signify lack of support to the compositor.
+        Text is UTF-8 encoded, and should include the cursor position, the
+        complete selection and additional characters before and after them.
+        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 text buffer.
+        Anchor is the byte offset of the selection anchor within text buffer.
+        If there is no selected text, anchor is the same as cursor.
+        If any preedit text is present, it is replaced with a cursor for the
+        purpose of this event.
+        Values set with this request are double-buffered. They will get applied
+        on the next zwp_text_input_v3.commit request, and stay valid until the
+        next enable or disable request.
+        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="int"/>
+      <arg name="anchor" type="int"/>
+    </request>
+    <enum name="change_cause">
+      <description summary="text change reason">
+        Reason for the change of surrounding text or cursor posision.
+      </description>
+      <entry name="input_method" value="0" summary="input method caused the change"/>
+      <entry name="other" value="1" summary="something else than the input method caused the change"/>
+    </enum>
+    <request name="set_text_change_cause">
+      <description summary="indicates the cause of surrounding text change">
+        Tells the compositor 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 request is double-buffered. It must be applied
+        and reset to initial at the next zwp_text_input_v3.commit request.
+        The initial value of cause is input_method.
+      </description>
+      <arg name="cause" type="uint" enum="change_cause"/>
+    </request>
+    <enum name="content_hint" bitfield="true">
+      <description summary="content hint">
+        Content hint is a bitmask to allow to modify the behavior of the text
+        input.
+      </description>
+      <entry name="none" value="0x0" summary="no special behavior"/>
+      <entry name="completion" value="0x1" summary="suggest word completions"/>
+      <entry name="spellcheck" value="0x2" summary="suggest word corrections"/>
+      <entry name="auto_capitalization" value="0x4" summary="switch to uppercase letters at the start of a sentence"/>
+      <entry name="lowercase" value="0x8" summary="prefer lowercase letters"/>
+      <entry name="uppercase" value="0x10" summary="prefer uppercase letters"/>
+      <entry name="titlecase" value="0x20" summary="prefer casing for titles and headings (can be language dependent)"/>
+      <entry name="hidden_text" value="0x40" summary="characters should be hidden"/>
+      <entry name="sensitive_data" value="0x80" summary="typed text should not be stored"/>
+      <entry name="latin" value="0x100" summary="just Latin characters should be entered"/>
+      <entry name="multiline" value="0x200" summary="the text input is multiline"/>
+    </enum>
+    <enum name="content_purpose">
+      <description summary="content purpose">
+        The content purpose allows to specify the primary purpose of a text
+        input.
+        This allows an input method to show special purpose input panels with
+        extra characters or to disallow some characters.
+      </description>
+      <entry name="normal" value="0" summary="default input, allowing all characters"/>
+      <entry name="alpha" value="1" summary="allow only alphabetic characters"/>
+      <entry name="digits" value="2" summary="allow only digits"/>
+      <entry name="number" value="3" summary="input a number (including decimal separator and sign)"/>
+      <entry name="phone" value="4" summary="input a phone number"/>
+      <entry name="url" value="5" summary="input an URL"/>
+      <entry name="email" value="6" summary="input an email address"/>
+      <entry name="name" value="7" summary="input a name of a person"/>
+      <entry name="password" value="8" summary="input a password (combine with sensitive_data hint)"/>
+      <entry name="pin" value="9" summary="input is a numeric password (combine with sensitive_data hint)"/>
+      <entry name="date" value="10" summary="input a date"/>
+      <entry name="time" value="11" summary="input a time"/>
+      <entry name="datetime" value="12" summary="input a date and time"/>
+      <entry name="terminal" value="13" summary="input for a terminal"/>
+    </enum>
+    <request name="set_content_type">
+      <description summary="set content purpose and hint">
+        Sets the content purpose and content hint. While the purpose is the
+        basic purpose of an input field, the hint flags allow to modify some of
+        the behavior.
+        Values set with this request are double-buffered. They will get applied
+        on the first zwp_text_input_v3.commit request after an enable request.
+        Subsequent attempts to update them may have no effect. The values
+        remain valid until the next enable or disable request.
+        The initial value for hint is none, and the initial value for purpose
+        is normal.
+      </description>
+      <arg name="hint" type="uint" enum="content_hint"/>
+      <arg name="purpose" type="uint" enum="content_purpose"/>
+    </request>
+    <request name="set_cursor_rectangle">
+      <description summary="set cursor position">
+        Marks an area around the cursor as a x, y, width, height rectangle in
+        surface local coordinates.
+        Allows the compositor to put a window with word suggestions near the
+        cursor, without obstructing the text being input.
+        If the client is unaware of the position of edited text, it should not
+        issue this request, to signify lack of support to the compositor.
+        Values set with this request are double-buffered. They will get applied
+        on the next zwp_text_input_v3.commit request, and stay valid until the
+        next enable or disable request.
+        The initial values describing a cursor rectangle are empty. That means
+        the text input does not support describing the cursor area. If the
+        empty values get applied, subsequent attempts to change them may have
+        no effect.
+      </description>
+      <arg name="x" type="int"/>
+      <arg name="y" type="int"/>
+      <arg name="width" type="int"/>
+      <arg name="height" type="int"/>
+    </request>
+    <request name="commit">
+      <description summary="commit state">
+        Atomically applies state changes recently sent to the compositor.
+        The commit request establishes and updates the state of the client, and
+        must be issued immediately after before the compositor
+        Text input state (enabled status, content purpose, content hint,
+        surrounding text and change cause, cursor rectangle) is conceptually
+        double-buffered within the context of a text input, i.e. between an
+        enable request and the following enable or disable request.
+        Protocol requests modify the pending state, as opposed to the current
+        state in use by the input method. A commit request atomically applies
+        all pending state, replacing the current state. After commit, the new
+        pending state is as documented for each related request.
+        The enable request plays a special role by indicating that the state
+        should be reset and updated with new values on the nearest commit.
+        Neither current nor pending state are modified unless noted otherwise.
+        The serial number identifies the current state of the
+        zwp_text_input_v3 object. The serial value of the Nth request issued
+        on the object must be the Nth number of an infinite sequence of
+        integers, in which each pair of equal values is separated by at least
+        4096 positions.
+      </description>
+      <arg name="serial" type="uint"/>
+    </request>
+    <event name="enter">
+      <description summary="enter event">
+        Notification that this seat's text-input focus is on a certain surface.
+        When the seat has the keyboard capability the text-input focus follows
+        the keyboard focus. This event sets the current surface for the
+        text-input object.
+      </description>
+      <arg name="surface" type="object" interface="wl_surface"/>
+    </event>
+    <event name="leave">
+      <description summary="leave event">
+        Notification that this seat's text-input focus is no longer on a
+        certain surface. The client should reset any preedit string previously
+        set.
+        The leave notification clears the current surface. It is sent before
+        the enter notification for the new focus.
+        When the seat has the keyboard capability the text-input focus follows
+        the keyboard focus.
+      </description>
+      <arg name="surface" type="object" interface="wl_surface"/>
+    </event>
+    <event name="preedit_string">
+      <description summary="pre-edit">
+        Notify when a new composing text (pre-edit) should be set at the
+        current cursor position. Any previously set composing text must be
+        removed. Any previously existing selected text must be removed.
+        The argument text contains the pre-edit string buffer.
+        The parameters cursor_begin and cursor_end are counted in bytes
+        relative to the beginning of the submitted text buffer. Cursor should
+        be hidden when both are equal to -1.
+        They could be represented by the client as a line if both values are
+        the same, or as a text highlight otherwise.
+        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.
+        The initial value of text is an empty string, and cursor_begin,
+        cursor_end and cursor_hidden are all 0.
+      </description>
+      <arg name="text" type="string" allow-null="true"/>
+      <arg name="cursor_begin" type="int"/>
+      <arg name="cursor_end" type="int"/>
+    </event>
+    <event name="commit_string">
+      <description summary="text commit">
+        Notify when text should be inserted into the editor widget. The text to
+        commit could be either just a single character after a key press or the
+        result of some composing (pre-edit).
+        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.
+        The initial value of text is an empty string.
+      </description>
+      <arg name="text" type="string" allow-null="true"/>
+    </event>
+    <event name="delete_surrounding_text">
+      <description summary="delete surrounding text">
+        Notify when the text around the current cursor position should be
+        deleted.
+        Before_length and after_length are the number of bytes before and after
+        the current cursor index (excluding the selection) to delete.
+        If a preedit text is present, in effect before_length is counted from
+        the beginning of it, and after_length from its end (see done event
+        sequence).
+        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.
+        The initial values of both before_length and after_length are 0.
+      </description>
+      <arg name="before_length" type="uint" summary="length of text before current cursor position"/>
+      <arg name="after_length" type="uint" summary="length of text after current cursor position"/>
+    </event>
+    <event name="done">
+      <description summary="apply changes">
+        Instruct the application to apply changes to state requested by the
+        preedit_string, commit_string and delete_surrounding_text events. The
+        state relating to these events is double-buffered, and each one
+        modifies the pending state. This event replaces the current state with
+        the pending state.
+        The application must 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_text_input_v3
+        object known to the compositor. The value of the serial argument must
+        come from the most recently received commit request. When the client
+        receives a done event with a serial different from the last serial
+        in the commit request, it must proceed as normal, except it must not
+        change the current state.
+        <arg name="serial" type="uint"/>
+      </description>
+    </event>
+  </interface>
+  <interface name="zwp_text_input_manager_v3" version="1">
+    <description summary="text input manager">
+      A factory for text-input objects. This object is a global singleton.
+    </description>
+    <request name="destroy" type="destructor">
+      <description summary="Destroy the wp_text_input_manager">
+        Destroy the wp_text_input_manager object.
+      </description>
+    </request>
+    <request name="get_text_input">
+      <description summary="create a new text input object">
+        Creates a new text-input object for a given seat.
+      </description>
+      <arg name="id" type="new_id" interface="zwp_text_input_v3"/>
+      <arg name="seat" type="object" interface="wl_seat"/>
+    </request>
+  </interface>

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