Implement fractional_scale_v1 and wp_viewport

This allows compositors to hint a non-integer scale to use on a window
which we can hook to Qt's existing fractional scaling support.

The viewport is used to communicate the relationship between buffer size
and logical size to the compositor. It is a non-integer alternative to
wl_buffer_scale

Change-Id: I1a850f1bcd40e8d04e241e18a538b11f18bc671c
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: David Edmundson <davidedmundson@kde.org>

2 files changed, 119 insertions, 0 deletions

diff --git a/src/3rdparty/protocol/fractional-scale-v1.xml b/src/3rdparty/protocol/fractional-scale-v1.xml
new file mode 100644
index 000000000..350bfc01e
--- /dev/null
+++ b/src/3rdparty/protocol/fractional-scale-v1.xml
@@ -0,0 +1,102 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="fractional_scale_v1">
+  <copyright>
+    Copyright © 2022 Kenny Levinsen
+
+    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 requesting fractional surface scales">
+    This protocol allows a compositor to suggest for surfaces to render at
+    fractional scales.
+
+    A client can submit scaled content by utilizing wp_viewport. This is done by
+    creating a wp_viewport object for the surface and setting the destination
+    rectangle to the surface size before the scale factor is applied.
+
+    The buffer size is calculated by multiplying the surface size by the
+    intended scale.
+
+    The wl_surface buffer scale should remain set to 1.
+
+    If a surface has a surface-local size of 100 px by 50 px and wishes to
+    submit buffers with a scale of 1.5, then a buffer of 150px by 75 px should
+    be used and the wp_viewport destination rectangle should be 100 px by 50 px.
+
+    For toplevel surfaces, the size is rounded halfway away from zero. The
+    rounding algorithm for subsurface position and size is not defined.
+  </description>
+
+  <interface name="wp_fractional_scale_manager_v1" version="1">
+    <description summary="fractional surface scale information">
+      A global interface for requesting surfaces to use fractional scales.
+    </description>
+
+    <request name="destroy" type="destructor">
+      <description summary="unbind the fractional surface scale interface">
+        Informs the server that the client will not be using this protocol
+        object anymore. This does not affect any other objects,
+        wp_fractional_scale_v1 objects included.
+      </description>
+    </request>
+
+    <enum name="error">
+      <entry name="fractional_scale_exists" value="0"
+        summary="the surface already has a fractional_scale object associated"/>
+    </enum>
+
+    <request name="get_fractional_scale">
+      <description summary="extend surface interface for scale information">
+        Create an add-on object for the the wl_surface to let the compositor
+        request fractional scales. If the given wl_surface already has a
+        wp_fractional_scale_v1 object associated, the fractional_scale_exists
+        protocol error is raised.
+      </description>
+      <arg name="id" type="new_id" interface="wp_fractional_scale_v1"
+           summary="the new surface scale info interface id"/>
+      <arg name="surface" type="object" interface="wl_surface"
+           summary="the surface"/>
+    </request>
+  </interface>
+
+  <interface name="wp_fractional_scale_v1" version="1">
+    <description summary="fractional scale interface to a wl_surface">
+      An additional interface to a wl_surface object which allows the compositor
+      to inform the client of the preferred scale.
+    </description>
+
+    <request name="destroy" type="destructor">
+      <description summary="remove surface scale information for surface">
+        Destroy the fractional scale object. When this object is destroyed,
+        preferred_scale events will no longer be sent.
+      </description>
+    </request>
+
+    <event name="preferred_scale">
+      <description summary="notify of new preferred scale">
+        Notification of a new preferred scale for this surface that the
+        compositor suggests that the client should use.
+
+        The sent scale is the numerator of a fraction with a denominator of 120.
+      </description>
+      <arg name="scale" type="uint" summary="the new preferred scale"/>
+    </event>
+  </interface>
+</protocol>
diff --git a/src/3rdparty/protocol/qt_attribution.json b/src/3rdparty/protocol/qt_attribution.json
index 7b81d5515..e30cb1b69 100644
--- a/src/3rdparty/protocol/qt_attribution.json
+++ b/src/3rdparty/protocol/qt_attribution.json
@@ -318,5 +318,22 @@
         "License": "MIT License",
         "LicenseFile": "MIT_LICENSE.txt",
         "Copyright": "Copyright © 2015-2016 Red Hat Inc."
+     },
+
+    {
+        "Id": "fractional-scale-v1",
+        "Name": "Wayland Fractional Scale Protocol",
+        "QDocModule": "qtwaylandcompositor",
+        "QtUsage": "Used in the Qt Wayland platform plugin",
+        "Files": "fractional-scale-v1.xml",
+
+        "Description": "Send a preferred scale to different clients",
+        "Homepage": "https://wayland.freedesktop.org",
+        "Version": "1",
+        "DownloadLocation": "https://gitlab.freedesktop.org/wayland/wayland-protocols/-/raw/1.31/unstable/fractional-scale/fractional-scale-v1.xml",
+        "LicenseId": "MIT",
+        "License": "MIT License",
+        "LicenseFile": "MIT_LICENSE.txt",
+        "Copyright": "Copyright © 2022 Kenny Levinsen"
      }
 ]