From 057086e389a78c600c0862ea331aa9b834ffbb43 Mon Sep 17 00:00:00 2001
From: Frank Praznik <[EMAIL REDACTED]>
Date: Fri, 15 Jul 2022 13:44:49 -0400
Subject: [PATCH] wayland: Add high resolution scroll wheel support
Update the Wayland core protocol spec file and add support for the new axis_value120 event to handle high resolution scroll wheels.
The axis_value120 replaces the axis_discrete event, which is no longer sent as of version 8 of the protocol. Note that unlike the axis_discrete event, no mention in the spec is made regarding how many axis_value120 events may occur per-axis per-frame, so the values are accumulated and committed when the pointer frame event occurs.
---
src/video/wayland/SDL_waylandevents.c | 119 ++++++++++---
src/video/wayland/SDL_waylandevents_c.h | 11 +-
wayland-protocols/wayland.xml | 226 ++++++++++++++++++++----
3 files changed, 295 insertions(+), 61 deletions(-)
diff --git a/src/video/wayland/SDL_waylandevents.c b/src/video/wayland/SDL_waylandevents.c
index 14a28430c98..94374ea72c9 100644
--- a/src/video/wayland/SDL_waylandevents.c
+++ b/src/video/wayland/SDL_waylandevents.c
@@ -632,37 +632,75 @@ pointer_handle_axis_common_v1(struct SDL_WaylandInput *input,
}
static void
-pointer_handle_axis_common(struct SDL_WaylandInput *input, SDL_bool discrete,
+pointer_handle_axis_common(struct SDL_WaylandInput *input, enum SDL_WaylandAxisEvent type,
uint32_t axis, wl_fixed_t value)
{
enum wl_pointer_axis a = axis;
if (input->pointer_focus) {
switch (a) {
- case WL_POINTER_AXIS_VERTICAL_SCROLL:
- if (discrete) {
- /* this is a discrete axis event so we process it and flag
- * to ignore future continuous axis events in this frame */
- input->pointer_curr_axis_info.is_y_discrete = SDL_TRUE;
- } else if(input->pointer_curr_axis_info.is_y_discrete) {
- /* this is a continuous axis event and we have already
- * processed a discrete axis event before so we ignore it */
- break;
+ case WL_POINTER_AXIS_VERTICAL_SCROLL:
+ switch (type) {
+ case AXIS_EVENT_VALUE120:
+ /*
+ * High resolution scroll event. The spec doesn't state that axis_value120
+ * events are limited to one per frame, so the values are accumulated.
+ */
+ if (input->pointer_curr_axis_info.y_axis_type != AXIS_EVENT_VALUE120) {
+ input->pointer_curr_axis_info.y_axis_type = AXIS_EVENT_VALUE120;
+ input->pointer_curr_axis_info.y = 0.0f;
}
- input->pointer_curr_axis_info.y = 0 - (float)wl_fixed_to_double(value);
+ input->pointer_curr_axis_info.y += 0 - (float)wl_fixed_to_double(value);
break;
- case WL_POINTER_AXIS_HORIZONTAL_SCROLL:
- if (discrete) {
- /* this is a discrete axis event so we process it and flag
- * to ignore future continuous axis events in this frame */
- input->pointer_curr_axis_info.is_x_discrete = SDL_TRUE;
- } else if(input->pointer_curr_axis_info.is_x_discrete) {
- /* this is a continuous axis event and we have already
- * processed a discrete axis event before so we ignore it */
- break;
+ case AXIS_EVENT_DISCRETE:
+ /*
+ * This is a discrete axis event, so we process it and set the
+ * flag to ignore future continuous axis events in this frame.
+ */
+ if (input->pointer_curr_axis_info.y_axis_type != AXIS_EVENT_DISCRETE) {
+ input->pointer_curr_axis_info.y_axis_type = AXIS_EVENT_DISCRETE;
+ input->pointer_curr_axis_info.y = 0 - (float)wl_fixed_to_double(value);
+ }
+ break;
+ case AXIS_EVENT_CONTINUOUS:
+ /* Only process continuous events if no discrete events have been received. */
+ if (input->pointer_curr_axis_info.y_axis_type == AXIS_EVENT_CONTINUOUS) {
+ input->pointer_curr_axis_info.y = 0 - (float)wl_fixed_to_double(value);
+ }
+ break;
+ }
+ break;
+ case WL_POINTER_AXIS_HORIZONTAL_SCROLL:
+ switch (type) {
+ case AXIS_EVENT_VALUE120:
+ /*
+ * High resolution scroll event. The spec doesn't state that axis_value120
+ * events are limited to one per frame, so the values are accumulated.
+ */
+ if (input->pointer_curr_axis_info.x_axis_type != AXIS_EVENT_VALUE120) {
+ input->pointer_curr_axis_info.x_axis_type = AXIS_EVENT_VALUE120;
+ input->pointer_curr_axis_info.x = 0.0f;
+ }
+ input->pointer_curr_axis_info.x += (float)wl_fixed_to_double(value);
+ break;
+ case AXIS_EVENT_DISCRETE:
+ /*
+ * This is a discrete axis event, so we process it and set the
+ * flag to ignore future continuous axis events in this frame.
+ */
+ if (input->pointer_curr_axis_info.x_axis_type != AXIS_EVENT_DISCRETE) {
+ input->pointer_curr_axis_info.x_axis_type = AXIS_EVENT_DISCRETE;
+ input->pointer_curr_axis_info.x = (float)wl_fixed_to_double(value);
}
- input->pointer_curr_axis_info.x = (float)wl_fixed_to_double(value);
break;
+ case AXIS_EVENT_CONTINUOUS:
+ /* Only process continuous events if no discrete events have been received. */
+ if (input->pointer_curr_axis_info.x_axis_type == AXIS_EVENT_CONTINUOUS) {
+ input->pointer_curr_axis_info.x = (float)wl_fixed_to_double(value);
+ }
+ break;
+ }
+ break;
}
}
}
@@ -674,7 +712,7 @@ pointer_handle_axis(void *data, struct wl_pointer *pointer,
struct SDL_WaylandInput *input = data;
if(wl_seat_get_version(input->seat) >= 5)
- pointer_handle_axis_common(input, SDL_FALSE, axis, value);
+ pointer_handle_axis_common(input, AXIS_EVENT_CONTINUOUS, axis, value);
else
pointer_handle_axis_common_v1(input, time, axis, value);
}
@@ -686,15 +724,29 @@ pointer_handle_frame(void *data, struct wl_pointer *pointer)
SDL_WindowData *window = input->pointer_focus;
float x, y;
- if (input->pointer_curr_axis_info.is_x_discrete)
- x = input->pointer_curr_axis_info.x;
- else
+ switch(input->pointer_curr_axis_info.x_axis_type) {
+ case AXIS_EVENT_CONTINUOUS:
x = input->pointer_curr_axis_info.x / WAYLAND_WHEEL_AXIS_UNIT;
+ break;
+ case AXIS_EVENT_DISCRETE:
+ x = input->pointer_curr_axis_info.x;
+ break;
+ case AXIS_EVENT_VALUE120:
+ x = input->pointer_curr_axis_info.x / 120.0f;
+ break;
+ }
- if (input->pointer_curr_axis_info.is_y_discrete)
- y = input->pointer_curr_axis_info.y;
- else
+ switch(input->pointer_curr_axis_info.y_axis_type) {
+ case AXIS_EVENT_CONTINUOUS:
y = input->pointer_curr_axis_info.y / WAYLAND_WHEEL_AXIS_UNIT;
+ break;
+ case AXIS_EVENT_DISCRETE:
+ y = input->pointer_curr_axis_info.y;
+ break;
+ case AXIS_EVENT_VALUE120:
+ y = input->pointer_curr_axis_info.y / 120.0f;
+ break;
+ }
/* clear pointer_curr_axis_info for next frame */
SDL_memset(&input->pointer_curr_axis_info, 0, sizeof input->pointer_curr_axis_info);
@@ -725,9 +777,17 @@ pointer_handle_axis_discrete(void *data, struct wl_pointer *pointer,
{
struct SDL_WaylandInput *input = data;
- pointer_handle_axis_common(input, SDL_TRUE, axis, wl_fixed_from_int(discrete));
+ pointer_handle_axis_common(input, AXIS_EVENT_DISCRETE, axis, wl_fixed_from_int(discrete));
}
+static void
+pointer_handle_axis_value120(void *data, struct wl_pointer *pointer,
+ uint32_t axis, int32_t value120)
+{
+ struct SDL_WaylandInput *input = data;
+
+ pointer_handle_axis_common(input, AXIS_EVENT_VALUE120, axis, wl_fixed_from_int(value120));
+}
static const struct wl_pointer_listener pointer_listener = {
pointer_handle_enter,
@@ -739,6 +799,7 @@ static const struct wl_pointer_listener pointer_listener = {
pointer_handle_axis_source, // Version 5
pointer_handle_axis_stop, // Version 5
pointer_handle_axis_discrete, // Version 5
+ pointer_handle_axis_value120 // Version 8
};
static void
diff --git a/src/video/wayland/SDL_waylandevents_c.h b/src/video/wayland/SDL_waylandevents_c.h
index 9bcb2c9b155..491c3852660 100644
--- a/src/video/wayland/SDL_waylandevents_c.h
+++ b/src/video/wayland/SDL_waylandevents_c.h
@@ -29,6 +29,13 @@
#include "SDL_waylanddatamanager.h"
#include "SDL_waylandkeyboard.h"
+enum SDL_WaylandAxisEvent
+{
+ AXIS_EVENT_CONTINUOUS = 0,
+ AXIS_EVENT_DISCRETE,
+ AXIS_EVENT_VALUE120
+};
+
struct SDL_WaylandTabletSeat;
struct SDL_WaylandTabletObjectListNode {
@@ -113,10 +120,10 @@ struct SDL_WaylandInput {
/* information about axis events on current frame */
struct {
- SDL_bool is_x_discrete;
+ enum SDL_WaylandAxisEvent x_axis_type;
float x;
- SDL_bool is_y_discrete;
+ enum SDL_WaylandAxisEvent y_axis_type;
float y;
} pointer_curr_axis_info;
diff --git a/wayland-protocols/wayland.xml b/wayland-protocols/wayland.xml
index 471daf668e3..10781cf1679 100644
--- a/wayland-protocols/wayland.xml
+++ b/wayland-protocols/wayland.xml
@@ -179,7 +179,7 @@
the related request is done.
</description>
- <event name="done">
+ <event name="done" type="destructor">
<description summary="done event">
Notify the client when the related request is done.
</description>
@@ -187,7 +187,7 @@
</event>
</interface>
- <interface name="wl_compositor" version="4">
+ <interface name="wl_compositor" version="5">
<description summary="the compositor singleton">
A compositor. This object is a singleton global. The
compositor is in charge of combining the contents of multiple
@@ -258,6 +258,12 @@
for the pool from the file descriptor passed when the pool was
created, but using the new size. This request can only be
used to make the pool bigger.
+
+ This request only changes the amount of bytes that are mmapped
+ by the server and does not touch the file corresponding to the
+ file descriptor passed at creation time. It is the client's
+ responsibility to ensure that the file is at least as big as
+ the new pool size.
</description>
<arg name="size" type="int" summary="new size of the pool, in bytes"/>
</request>
@@ -271,8 +277,8 @@
Clients can create wl_shm_pool objects using the create_pool
request.
- At connection setup time, the wl_shm object emits one or more
- format events to inform clients about the valid pixel formats
+ On binding the wl_shm object one or more format events
+ are emitted to inform clients about the valid pixel formats
that can be used for buffers.
</description>
@@ -296,6 +302,9 @@
The drm format codes match the macros defined in drm_fourcc.h, except
argb8888 and xrgb8888. The formats actually supported by the compositor
will be reported by the format event.
+
+ For all wl_shm formats and unless specified in another protocol
+ extension, pre-multiplied alpha is used for pixel values.
</description>
<!-- Note to protocol writers: don't update this list manually, instead
run the automated script that keeps it in sync with drm_fourcc.h. -->
@@ -403,6 +412,10 @@
<entry name="nv15" value="0x3531564e" summary="2x2 subsampled Cr:Cb plane"/>
<entry name="q410" value="0x30313451"/>
<entry name="q401" value="0x31303451"/>
+ <entry name="xrgb16161616" value="0x38345258" summary="[63:0] x:R:G:B 16:16:16:16 little endian"/>
+ <entry name="xbgr16161616" value="0x38344258" summary="[63:0] x:B:G:R 16:16:16:16 little endian"/>
+ <entry name="argb16161616" value="0x38345241" summary="[63:0] A:R:G:B 16:16:16:16 little endian"/>
+ <entry name="abgr16161616" value="0x38344241" summary="[63:0] A:B:G:R 16:16:16:16 little endian"/>
</enum>
<request name="create_pool">
@@ -431,10 +444,15 @@
<interface name="wl_buffer" version="1">
<description summary="content for a wl_surface">
A buffer provides the content for a wl_surface. Buffers are
- created through factory interfaces such as wl_drm, wl_shm or
- similar. It has a width and a height and can be attached to a
- wl_surface, but the mechanism by which a client provides and
- updates the contents is defined by the buffer factory interface.
+ created through factory interfaces such as wl_shm, wp_linux_buffer_params
+ (from the linux-dmabuf protocol extension) or similar. It has a width and
+ a height and can be attached to a wl_surface, but the mechanism by which a
+ client provides and updates the contents is defined by the buffer factory
+ interface.
+
+ If the buffer uses a format that has an alpha channel, the alpha channel
+ is assumed to be premultiplied in the color channels unless otherwise
+ specified.
</description>
<request name="destroy" type="destructor">
@@ -878,7 +896,7 @@
which will subsequently be used in either the
data_device.enter event (for drag-and-drop) or the
data_device.selection event (for selections). Immediately
- following the data_device_data_offer event, the new data_offer
+ following the data_device.data_offer event, the new data_offer
object will send out data_offer.offer events to describe the
mime types it offers.
</description>
@@ -948,9 +966,10 @@
immediately before receiving keyboard focus and when a new
selection is set while the client has keyboard focus. The
data_offer is valid until a new data_offer or NULL is received
- or until the client loses keyboard focus. The client must
- destroy the previous selection data_offer, if any, upon receiving
- this event.
+ or until the client loses keyboard focus. Switching surface with
+ keyboard focus within the same client doesn't mean a new selection
+ will be sent. The client must destroy the previous selection
+ data_offer, if any, upon receiving this event.
</description>
<arg name="id" type="object" interface="wl_data_offer" allow-null="true"
summary="selection data_offer object"/>
@@ -1038,7 +1057,8 @@
a basic surface.
Note! This protocol is deprecated and not intended for production use.
- For desktop-style user interfaces, use xdg_shell.
+ For desktop-style user interfaces, use xdg_shell. Compositors and clients
+ should not implement this interface.
</description>
<enum name="error">
@@ -1332,7 +1352,7 @@
</event>
</interface>
- <interface name="wl_surface" version="4">
+ <interface name="wl_surface" version="5">
<description summary="an onscreen surface">
A surface is a rectangular area that may be displayed on zero
or more outputs, and shown any number of times at the compositor's
@@ -1384,6 +1404,7 @@
<entry name="invalid_scale" value="0" summary="buffer scale value is invalid"/>
<entry name="invalid_transform" value="1" summary="buffer transform value is invalid"/>
<entry name="invalid_size" value="2" summary="buffer size is invalid"/>
+ <entry name="invalid_offset" value="3" summary="buffer offset is invalid"/>
</enum>
<request name="destroy" type="destructor">
@@ -1406,7 +1427,14 @@
buffer's upper left corner, relative to the current buffer's upper
left corner, in surface-local coordinates. In other words, the
x and y, combined with the new surface size define in which
- directions the surface's size changes.
+ directions the surface's size changes. Setting anything other than 0
+ as x and y arguments is discouraged, and should instead be replaced
+ with using the separate wl_surface.offset request.
+
+ When the bound wl_surface version is 5 or higher, passing any
+ non-zero x or y is a protocol violation, and will result in an
+ 'invalid_offset' error being raised. To achieve equivalent semantics,
+ use wl_surface.offset.
Surface contents are double-buffered state, see wl_surface.commit.
@@ -1434,9 +1462,12 @@
from the same backing storage or use wp_linux_buffer_release.
Destroying the wl_buffer after wl_buffer.release does not change
- the surface contents. However, if the client destroys the
- wl_buffer before receiving the wl_buffer.release event, the surface
- contents become undefined immediately.
+ the surface contents. Destroying the wl_buffer before wl_buffer.release
+ is allowed as long as the underlying buffer storage isn't re-used (this
+ can happen e.g. on client process termination). However, if the client
+ destroys the wl_buffer before receiving the wl_buffer.release event and
+ mutates the underlying buffer storage, the surface contents become
+ undefined immediately.
If wl_surface.attach is sent with a NULL wl_buffer, the
following wl_surface.commit will remove the surface content.
@@ -1734,9 +1765,30 @@
<arg name="width" type="int" summary="width of damage rectangle"/>
<arg name="height" type="int" summary="height of damage rectangle"/>
</request>
+
+ <!-- Version 5 additions -->
+
+ <request name="offset" since="5">
+ <description summary="set the surface contents offset">
+ The x and y arguments specify the location of the new pending
+ buffer's upper left corner, relative to the current buffer's upper
+ left corner, in surface-local coordinates. In other words, the
+ x and y, combined with the new surface size define in which
+ directions the surface's size changes.
+
+ Surface location offset is double-buffered state, see
+ wl_surface.commit.
+
+ This request is semantically equivalent to and the replaces the x and y
+ arguments in the wl_surface.attach request in wl_surface versions prior
+ to 5. See wl_surface.attach for details.
+ </description>
+ <arg name="x" type="int" summary="surface-local x coordinate"/>
+ <arg name="y" type="int" summary="surface-local y coordinate"/>
+ </request>
</interface>
- <interface name="wl_seat" version="7">
+ <interface name="wl_seat" version="8">
<description summary="group of input devices">
A seat is a group of keyboards, pointer and touch devices. This
object is published as a global during start up, or when such a
@@ -1838,9 +1890,22 @@
<event name="name" since="2">
<description summary="unique identifier for this seat">
- In a multiseat configuration this can be used by the client to help
- identify which physical devices the seat represents. Based on
- the seat configuration used by the compositor.
+ In a multi-seat configuration the seat name can be used by clients to
+ help identify which physical devices the seat represents.
+
+ The seat name is a UTF-8 string with no convention defined for its
+ contents. Each name is unique among all wl_seat globals. The name is
+ only guaranteed to be unique for the current compositor instance.
+
+ The same seat names are used for all clients. Thus, the name can be
+ shared across processes to refer to a specific wl_seat global.
+
+ The name event is sent after binding to the seat global. This event is
+ only sent once per seat object, and the name does not change over the
+ lifetime of the wl_seat global.
+
+ Compositors may re-use the same seat name if the wl_seat global is
+ destroyed and re-created later.
</description>
<arg name="name" type="string" summary="seat identifier"/>
</event>
@@ -1856,7 +1921,7 @@
</interface>
- <interface name="wl_pointer" version="7">
+ <interface name="wl_pointer" version="8">
<description summary="pointer input device">
The wl_pointer interface represents one or more input devices,
such as mice, which control the pointer location and pointer_focus
@@ -1905,6 +1970,10 @@
wl_surface is no longer used as the cursor. When the use as a
cursor ends, the current and pending input regions become
undefined, and the wl_surface is unmapped.
+
+ The serial parameter must match the latest wl_pointer.enter
+ serial number sent to the client. Otherwise the request will be
+ ignored.
</description>
<arg name="serial" type="uint" summary="serial number of the enter event"/>
<arg name="surface" type="object" interface="wl_surface" allow-null="true"
@@ -2152,6 +2221,9 @@
This event carries the axis value of the wl_pointer.axis event in
discrete steps (e.g. mouse wheel clicks).
+ This event is deprecated with wl_pointer version 8 - this event is not
+ sent to clients supporting version 8 or later.
+
This event does not occur on its own, it is coupled with a
wl_pointer.axis event that represents this axis value on a
continuous scale. The protocol guarantees that each axis_discrete
@@ -2159,7 +2231,8 @@
axis number within the same wl_pointer.frame. Note that the protocol
allows for other events to occur between the axis_discrete and
its coupled axis event, including other axis_discrete or axis
- events.
+ events. A wl_pointer.frame must not contain more than one axis_discrete
+ event per axis type.
This event is optional; continuous scrolling devices
like two-finger scrolling on touchpads do not have discrete
@@ -2177,9 +2250,37 @@
<arg name="axis" type="uint" enum="axis" summary="axis type"/>
<arg name="discrete" type="int" summary="number of steps"/>
</event>
+
+ <event name="axis_value120" since="8">
+ <description summary="axis high-resolution scroll event">
+ Discrete high-resolution scroll information.
+
+ This event carries high-resolution wheel scroll information,
+ with each multiple of 120 representing one logical scroll step
+ (a wheel detent). For example, an axis_value120 of 30 is one quarter of
+ a logical scroll step in the positive direction, a value120 of
+ -240 are two logical scroll steps in the negative direction within the
+ same hardware event.
+ Clients that rely on discrete scrolling should accumulate the
+ value120 to multiples of 120 before processing the event.
+
+ The value120 must not be zero.
+
+ This event replaces the wl_pointer.axis_discrete event in clients
+ supporting wl_pointer version 8 or later.
+
+ Where a wl_pointer.axis_source event occurs in the same
+ wl_pointer.frame, the axis source applies to this event.
+
+ The order of wl_pointer.axis_value120 and wl_pointer.axis_source is
+ not guaranteed.
+ </description>
+ <arg name="axis" type="uint" enum="axis" summary="axis type"/>
+ <arg name="value120" type="int" summary="scroll distance as fraction of 120"/>
+ </event>
</interface>
- <interface name="wl_keyboard" version="7">
+ <interface name="wl_keyboard" version="8">
<description summary="keyboard input device">
The wl_keyboard interface represents one or more keyboards
associated with a seat.
@@ -2193,13 +2294,14 @@
<entry name="no_keymap" value="0"
summary="no keymap; client must understand how to interpret the raw keycode"/>
<entry name="xkb_v1" value="1"
- summary="libxkbcommon compatible; to determine the xkb keycode, clients must add 8 to the key event keycode"/>
+ summary="libxkbcommon compatible, null-terminated string; to determine the xkb keycode, clients must add 8 to the key event keycode"/>
</enum>
<event name="keymap">
<description summary="keyboard mapping">
This event provides a file descriptor to the client which can be
- memory-mapped to provide a keyboard mapping description.
+ memory-mapped in read-only mode to provide a keyboard mapping
+ description.
From version 7 onwards, the fd must be mapped with MAP_PRIVATE by
the recipient, as MAP_SHARED may fail.
@@ -2305,7 +2407,7 @@
</event>
</interface>
- <interface name="wl_touch" version="7">
+ <interface name="wl_touch" version="8">
<description summary="touchscreen input device">
The wl_touch interface represents a touchscreen
associated with a seat.
@@ -2449,7 +2551,7 @@
</event>
</interface>
- <interface name="wl_output" version="3">
+ <interface name="wl_output" version="4">
<description summary="compositor output region">
An output describes part of the compositor geometry. The
compositor works in the 'compositor coordinate system' and an
@@ -2505,12 +2607,15 @@
The physical size can be set to zero if it doesn't make sense for this
output (e.g. for projectors or virtual outputs).
+ The geometry event will be followed by a done event (starting from
+ version 2).
+
Note: wl_output only advertises partial information about the output
position and identification. Some compositors, for instance those not
implementing a desktop-style output layout or those exposing virtual
outputs, might fake this information. Instead of using x and y, clients
should use xdg_output.logical_position. Instead of using make and model,
- clients should use xdg_output.name and xdg_output.description.
+ clients should use name and description.
</description>
<arg name="x" type="int"
summary="x position within the global compositor space"/>
@@ -2566,6 +2671,9 @@
The vertical refresh rate can be set to zero if it doesn't make
sense for this output (e.g. for virtual outputs).
+ The mode event will be followed by a done event (starting from
+ version 2).
+
Clients should not use the refresh rate to schedule frames. Instead,
they should use the wl_surface.frame event or the presentation-time
protocol.
@@ -2612,6 +2720,8 @@
the scale of the output. That way the compositor can
avoid scaling the surface, and the client can supply
a higher detail image.
+
+ The scale event will be followed by a done event.
</description>
<arg name="factor" type="int" summary="scaling factor of output"/>
</event>
@@ -2624,6 +2734,62 @@
use the output object anymore.
</description>
</request>
+
+ <!-- Version 4 additions -->
+
+ <event name="name" since="4">
+ <description summary="name of this output">
+ Many compositors will assign user-friendly names to their outputs, show
+ them to the user, allow the user to refer to an output, etc. The client
+ may wish to know this name as well to offer the user similar behaviors.
+
+ The name is a UTF-8 string with no convention defined for its contents.
+ Each name is unique among all wl_output globals. The name is only
+ guaranteed to be unique for the compositor instance.
+
+ The same output name is used for all clients for a given wl_output
+ global. Thus, the name can be shared across processes to refer to a
+ specific wl_output global.
+
+ The name is not guaranteed to be persistent across sessions, thus cannot
+ be used to reliably identify an output in e.g. configuration files.
+
+ Examples of names include 'HDMI-A-1', 'WL-1', 'X11-1', etc. However, do
+ not assume that the name is a reflection of an underlying DRM connector,
+ X11 connection, etc.
+
+ The name event is sent after binding the output object. This event is
+ only sent once per output object, and the name does not change over the
+ lifetime of the wl_output global.
+
+ Compositors may re-use the same output name if the wl_output global is
+ destroyed and re-created later. Compositors should avoid re-using the
+ same name if possible.
+
+ The name event will be followed by a done event.
+ </description>
+ <arg name="name" type="string" summary="output name"/>
+ </event>
+
+ <event name="description" since="4">
+ <description summary="human-readable description of this output">
+ Many compositors can produce human-readable descriptions of their
+ outputs. The client may wish to know this description as well, e.g. for
+ output selection purposes.
+
+ The description is a UTF-8 string with no convention defined for its
+ contents. The description is not guaranteed to be unique among all
+ wl_output globals. Examples might include 'Foocorp 11" Display' or
+ 'Virtual X11 output via :1'.
+
+ The description event is sent after binding the output object and
+ whenever the description changes. The description is optional, and may
+ not be sent at all.
+
+ The description event will be followed by a done event.
+ </description>
+ <arg name="description" type="string" summary="output description"/>
+ </event>
</interface>
<interface name="wl_region" version="1">