staging: add ext-background-effect-v1

This protocol allows the client to specify a region behind the surface that should
be blurred, with the intention to improve the visuals of for example panels or
terminals.

This protocol is roughly based on the org_kde_kwin_blur protocol, which has been
in use since 2015. The protocol is made more generically though, so that other
related effects can be added in the future, like for example contrast improvements.

Signed-off-by: Xaver Hugl <xaver.hugl@kde.org>

meson.build

@@ -52,6 +52,7 @@ staging_protocols = {
 	'content-type': ['v1'],
 	'cursor-shape': ['v1'],
 	'drm-lease': ['v1'],
+	'ext-background-effect': ['v1'],
 	'ext-data-control': ['v1'],
 	'ext-foreign-toplevel-list': ['v1'],
 	'ext-idle-notify': ['v1'],

staging/ext-background-effect/README

@@ -0,0 +1,6 @@
+ext_blur protocol
+
+Maintainers:
+David Edmundson <davidedmundson@kde.org>
+Vlad Zahorodnii <vlad.zahorodnii@kde.org>
+Xaver Hugl <xaver.hugl@kde.org>

staging/ext-background-effect/ext-background-effect-v1.xml

@@ -0,0 +1,129 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="ext_background_effect_v1">
+  <copyright>
+    Copyright (C) 2015 Martin Gräßlin
+    Copyright (C) 2015 Marco Martin
+    Copyright (C) 2020 Vlad Zahorodnii
+    Copyright (C) 2024 Xaver Hugl
+
+    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>
+
+  <interface name="ext_background_effect_manager_v1" version="1">
+    <description summary="background effect factory">
+      This protocol provides a way to improve visuals of translucent surfaces
+      by applying effects like blur to the background behind them.
+
+      The capabilities are send when the global is bound, and every time they
+      change. Note that when the capability goes away, the corresponding effect
+      is no longer applied by the compositor, even if it was set before.
+
+      Warning! The protocol described in this file is currently in the testing
+      phase. Backward compatible changes may be added together with the
+      corresponding interface version bump. Backward incompatible changes can
+      only be done by creating a new major version of the extension.
+    </description>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy the background effect manager">
+        Informs the server that the client will no longer be using this
+        protocol object. Existing objects created by this object are not
+        affected.
+      </description>
+    </request>
+
+    <enum name="error">
+      <entry name="background_effect_exists" value="0"
+             summary="the surface already has a background effect object"/>
+    </enum>
+
+    <enum name="capability" bitfield="true">
+      <entry name="blur" value="0"
+             summary="the compositor supports applying blur"/>
+    </enum>
+
+    <event name="capabilities">
+      <description summary="capabilities of the compositor"/>
+      <arg name="flags" type="uint" enum="capability"/>
+    </event>
+
+    <request name="get_background_effect">
+      <description summary="get a background effects object">
+        Instantiate an interface extension for the given wl_surface to add
+        effects like blur for the background behind it.
+
+        If the given wl_surface already has a ext_background_effect_surface_v1
+        object associated, the background_effect_exists protocol error will be
+        raised.
+      </description>
+      <arg name="id" type="new_id" interface="ext_background_effect_surface_v1"
+           summary="the new ext_background_effect_surface_v1 object"/>
+      <arg name="surface" type="object" interface="wl_surface"
+           summary="the surface"/>
+    </request>
+  </interface>
+
+  <interface name="ext_background_effect_surface_v1" version="1">
+    <description summary="background effects for a surface">
+      The background effect object provides a way to specify a region behind
+      a surface that should have background effects like blur applied.
+
+      If the wl_surface associated with the ext_background_effect_surface_v1
+      object has been destroyed, this object becomes inert.
+    </description>
+
+    <request name="destroy" type="destructor">
+      <description summary="release the blur object">
+        Informs the server that the client will no longer be using this protocol
+        object. The effect regions will be removed on the next commit.
+      </description>
+    </request>
+
+    <enum name="error">
+      <entry name="surface_destroyed" value="0"
+             summary="the associated surface has been destroyed"/>
+    </enum>
+
+    <request name="set_blur_region">
+      <description summary="set blur region">
+        This request sets the region of the surface that will have its
+        background blurred.
+
+        The blur region is specified in the surface-local coordinates, and
+        clipped by the compositor to the surface size.
+
+        The initial value for the blur region is empty. Setting the pending
+        blur region has copy semantics, and the wl_region object can be
+        destroyed immediately. A NULL wl_region removes the effect.
+
+        The blur region is double-buffered state, and will be applied on
+        the next wl_surface.commit.
+
+        The blur algorithm is subject to compositor policies.
+
+        If the associated surface has been destroyed, the surface_destroyed
+        error will be raised.
+      </description>
+      <arg name="region" type="object" interface="wl_region" allow-null="true"
+           summary="blur region of the surface"/>
+    </request>
+
+  </interface>
+</protocol>