From 96149c7e28e41a2d65464fee81b364b3f2474e64 Mon Sep 17 00:00:00 2001
From: Florian Bruhin <me@the-compiler.org>
Date: Wed, 9 Jun 2021 10:22:17 +0200
Subject: Add content.prefers_reduced_motion

Closes #6530
---
 doc/changelog.asciidoc                         |  6 ++++
 doc/help/settings.asciidoc                     | 16 +++++++++++
 qutebrowser/config/configdata.yml              | 13 +++++++++
 qutebrowser/config/qtargs.py                   |  6 +++-
 tests/end2end/data/prefers_reduced_motion.html | 38 ++++++++++++++++++++++++++
 tests/end2end/test_invocations.py              | 20 ++++++++++++++
 6 files changed, 98 insertions(+), 1 deletion(-)
 create mode 100644 tests/end2end/data/prefers_reduced_motion.html

diff --git a/doc/changelog.asciidoc b/doc/changelog.asciidoc
index 83d8a9601..02d388517 100644
--- a/doc/changelog.asciidoc
+++ b/doc/changelog.asciidoc
@@ -19,6 +19,12 @@ breaking changes (such as renamed commands) can happen in minor releases.
 v2.3.0 (unreleased)
 -------------------
 
+Added
+~~~~~
+
+- New `content.prefers_reduced_motion` setting to request websites to reduce
+  non-essential motion/animations.
+
 Changed
 ~~~~~~~
 
diff --git a/doc/help/settings.asciidoc b/doc/help/settings.asciidoc
index fb208e48c..2fc4440a6 100644
--- a/doc/help/settings.asciidoc
+++ b/doc/help/settings.asciidoc
@@ -187,6 +187,7 @@
 |<<content.pdfjs,content.pdfjs>>|Allow pdf.js to view PDF files in the browser.
 |<<content.persistent_storage,content.persistent_storage>>|Allow websites to request persistent storage quota via `navigator.webkitPersistentStorage.requestQuota`.
 |<<content.plugins,content.plugins>>|Enable plugins in Web pages.
+|<<content.prefers_reduced_motion,content.prefers_reduced_motion>>|Request websites to minimize non-essentials animations and motion.
 |<<content.print_element_backgrounds,content.print_element_backgrounds>>|Draw the background color and images also when the page is printed.
 |<<content.private_browsing,content.private_browsing>>|Open new windows in private browsing mode which does not record visited pages.
 |<<content.proxy,content.proxy>>|Proxy to use.
@@ -2607,6 +2608,21 @@ Type: <<types,Bool>>
 
 Default: +pass:[false]+
 
+[[content.prefers_reduced_motion]]
+=== content.prefers_reduced_motion
+Request websites to minimize non-essentials animations and motion.
+This results in the `prefers-reduced-motion` CSS media query to evaluate to `reduce` (rather than `no-preference`).
+
+This setting requires a restart.
+
+On QtWebEngine, this setting requires Qt 5.14 or newer.
+
+On QtWebKit, this setting is unavailable.
+
+Type: <<types,Bool>>
+
+Default: +pass:[false]+
+
 [[content.print_element_backgrounds]]
 === content.print_element_backgrounds
 Draw the background color and images also when the page is printed.
diff --git a/qutebrowser/config/configdata.yml b/qutebrowser/config/configdata.yml
index b85e84be2..78d9c9bf7 100644
--- a/qutebrowser/config/configdata.yml
+++ b/qutebrowser/config/configdata.yml
@@ -528,6 +528,19 @@ content.frame_flattening:
 
     This will flatten all the frames to become one scrollable page.
 
+content.prefers_reduced_motion:
+  default: false
+  type: Bool
+  backend:
+    QtWebEngine: Qt 5.14
+    QtWebKit: false
+  restart: true
+  desc: >-
+    Request websites to minimize non-essentials animations and motion.
+
+    This results in the `prefers-reduced-motion` CSS media query to evaluate to
+    `reduce` (rather than `no-preference`).
+
 content.site_specific_quirks:
   renamed: content.site_specific_quirks.enabled
 
diff --git a/qutebrowser/config/qtargs.py b/qutebrowser/config/qtargs.py
index cb17a0ced..c38ef5b01 100644
--- a/qutebrowser/config/qtargs.py
+++ b/qutebrowser/config/qtargs.py
@@ -334,7 +334,11 @@ def _qtwebengine_settings_args(versions: version.WebEngineVersions) -> Iterator[
         },
         'content.headers.referer': {
             'always': None,
-        }
+        },
+        'content.prefers_reduced_motion': {
+            True: '--force-prefers-reduced-motion',
+            False: None,
+        },
     }
     qt_514_ver = utils.VersionNumber(5, 14)
 
diff --git a/tests/end2end/data/prefers_reduced_motion.html b/tests/end2end/data/prefers_reduced_motion.html
new file mode 100644
index 000000000..a37d43864
--- /dev/null
+++ b/tests/end2end/data/prefers_reduced_motion.html
@@ -0,0 +1,38 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta charset="utf-8">
+        <title>Prefers reduced motion test</title>
+        <style>
+#reduce-text {
+    display: none;
+}
+#no-preference-text {
+    display: none;
+}
+
+@media (prefers-reduced-motion: no-preference) {
+    #no-preference-text {
+        display: inline;
+    }
+    #missing-support-text {
+        display: none;
+    }
+}
+
+@media (prefers-reduced-motion: reduce) {
+    #reduce-text {
+        display: inline;
+    }
+    #missing-support-text {
+        display: none;
+    }
+}
+        </style>
+    </head>
+    <body>
+        <p id="reduce-text">Reduced motion preference detected.</p>
+        <p id="no-preference-text">No preference detected.</p>
+        <p id="missing-support-text">Preference support missing.</p>
+    </body>
+</html>
diff --git a/tests/end2end/test_invocations.py b/tests/end2end/test_invocations.py
index 71cbfcb90..971be903c 100644
--- a/tests/end2end/test_invocations.py
+++ b/tests/end2end/test_invocations.py
@@ -752,6 +752,26 @@ def test_dark_mode_mathml(quteproc_new, request, qtbot):
     )
 
 
+@testutils.qt514
+@pytest.mark.parametrize('value, preference', [
+    ('true', 'Reduced motion'),
+    ('false', 'No'),
+])
+def test_prefers_reduced_motion(quteproc_new, request, qtbot, value, preference):
+    if not request.config.webengine:
+        pytest.skip("Skipped with QtWebKit")
+
+    args = _base_args(request.config) + [
+        '--temp-basedir',
+        '-s', 'content.prefers_reduced_motion', value,
+    ]
+    quteproc_new.start(args)
+
+    quteproc_new.open_path('data/prefers_reduced_motion.html')
+    content = quteproc_new.get_content()
+    assert content == f"{preference} preference detected."
+
+
 def test_unavailable_backend(request, quteproc_new):
     """Test starting with a backend which isn't available.
 
-- 
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