Add constant property QStyleHints::accessibility

This property bundles together accessibility settings that can be used
by styles to change how they draw different widgets and/or controls.

The only property that it contains currently is contrastPreference.
This property can be used to determine if the user has enabled a high
contrast setting on the platform that the Qt application is running on.

We might add more *accessibility* settings, like color blind hints, to
QAccessibilityHints in the future.

[ChangeLog][Gui][QStyleHints] Added class QAccessibilityHints, which can be
accessed from QStyleHints. This singleton contains a single property
contrastPreference which can be used to determine if the platform has
enabled a high contrast setting or not. More accessibility settings
might be added to QAccessibilityHints in the future.

Task-number: QTBUG-133595
Change-Id: I93c6be81d29f65058eeda00328f4d9e966921de6
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/gui/CMakeLists.txt

@@ -90,6 +90,7 @@ qt_internal_add_module(Gui
         image/qppmhandler.cpp image/qppmhandler_p.h
         image/qxbmhandler.cpp image/qxbmhandler_p.h
         image/qxpmhandler.cpp image/qxpmhandler_p.h
+        kernel/qaccessibilityhints.cpp kernel/qaccessibilityhints.h kernel/qaccessibilityhints_p.h
         kernel/qclipboard.cpp kernel/qclipboard.h
         kernel/qcursor.cpp kernel/qcursor.h kernel/qcursor_p.h
         kernel/qeventpoint.cpp kernel/qeventpoint.h kernel/qeventpoint_p.h

src/gui/kernel/qaccessibilityhints.cpp

@@ -0,0 +1,61 @@
+// Copyright (C) 2025 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#include "qaccessibilityhints.h"
+#include "qaccessibilityhints_p.h"
+
+QT_BEGIN_NAMESPACE
+
+void QAccessibilityHintsPrivate::updateContrastPreference(Qt::ContrastPreference contrastPreference)
+{
+    if (m_contrastPreference == contrastPreference)
+        return;
+    m_contrastPreference = contrastPreference;
+
+    Q_Q(QAccessibilityHints);
+    emit q->contrastPreferenceChanged(contrastPreference);
+}
+
+QAccessibilityHintsPrivate *QAccessibilityHintsPrivate::get(QAccessibilityHints *q)
+{
+    Q_ASSERT(q);
+    return q->d_func();
+}
+
+/*!
+    \class QAccessibilityHints
+    \since 6.10
+    \brief The QAccessibilityHints class contains platform specific accessibility hints and settings.
+    \inmodule QtGui
+
+    This class bundles together platform specific accessibility settings, and can be accessed from
+    \l QStyleHints::accessibility.
+
+    \sa QStyleHints
+*/
+
+QAccessibilityHints::QAccessibilityHints(QObject *parent)
+    : QObject(*(new QAccessibilityHintsPrivate), parent)
+{}
+
+/*!
+    \property QAccessibilityHints::contrastPreference
+    \brief The contrast mode set by the system.
+
+    This property can be used by the application to determine what contrast settings the system
+    is currently using.
+
+    Qt styles use this property in order to adjust palette colors and outlines.
+
+    \sa Qt::ColorScheme, QGuiApplication::palette(), QEvent::PaletteChange
+    \since 6.10
+*/
+Qt::ContrastPreference QAccessibilityHints::contrastPreference() const
+{
+    Q_D(const QAccessibilityHints);
+    return d->m_contrastPreference;
+}
+
+QT_END_NAMESPACE
+
+#include "moc_qaccessibilityhints.cpp"

src/gui/kernel/qaccessibilityhints.h

@@ -0,0 +1,30 @@
+// Copyright (C) 2025 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#ifndef QACCESSIBILITYHINTS_H
+#define QACCESSIBILITYHINTS_H
+
+#include <QtGui/qtguiglobal.h>
+#include <QtCore/qobject.h>
+
+QT_BEGIN_NAMESPACE
+
+class QAccessibilityHintsPrivate;
+
+class Q_GUI_EXPORT QAccessibilityHints : public QObject
+{
+    Q_OBJECT
+    Q_DECLARE_PRIVATE(QAccessibilityHints)
+    Q_PROPERTY(Qt::ContrastPreference contrastPreference READ contrastPreference NOTIFY contrastPreferenceChanged FINAL REVISION(6, 10))
+
+public:
+    explicit QAccessibilityHints(QObject *parent = nullptr);
+    Qt::ContrastPreference contrastPreference() const;
+
+Q_SIGNALS:
+    void contrastPreferenceChanged(Qt::ContrastPreference contrastPreference);
+};
+
+QT_END_NAMESPACE
+
+#endif // QACCESSIBILITYHINTS_H

src/gui/kernel/qaccessibilityhints_p.h

@@ -0,0 +1,37 @@
+// Copyright (C) 2025 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#ifndef QACCESSIBILITYHINTS_P_H
+#define QACCESSIBILITYHINTS_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "qaccessibilityhints.h"
+
+#include <QtCore/private/qobject_p.h>
+
+QT_BEGIN_NAMESPACE
+
+class QAccessibilityHintsPrivate : public QObjectPrivate
+{
+    Q_DECLARE_PUBLIC(QAccessibilityHints)
+public:
+    void updateContrastPreference(Qt::ContrastPreference contrastPreference);
+
+    static QAccessibilityHintsPrivate *get(QAccessibilityHints *q);
+private:
+    Qt::ContrastPreference m_contrastPreference = Qt::ContrastPreference::NoPreference;
+};
+
+QT_END_NAMESPACE
+
+#endif // QACCESSIBILITYHINTS_P_H

src/gui/kernel/qguiapplication.cpp

@@ -1589,8 +1589,7 @@ void QGuiApplicationPrivate::createPlatformIntegration()
     Q_UNUSED(platformExplicitlySelected);
 
     init_platform(QLatin1StringView(platformName), platformPluginPath, platformThemeName, argc, argv);
-    if (const QPlatformTheme *theme = platformTheme())
-        QStyleHintsPrivate::get(QGuiApplication::styleHints())->updateColorScheme(theme->colorScheme());
+    QStyleHintsPrivate::get(QGuiApplication::styleHints())->update(platformTheme());
 
     if (!icon.isEmpty())
         forcedWindowIcon = QDir::isAbsolutePath(icon) ? QIcon(icon) : QIcon::fromTheme(icon);
@@ -2820,10 +2819,7 @@ void QGuiApplicationPrivate::processThemeChanged(QWindowSystemInterfacePrivate::
 
 void QGuiApplicationPrivate::handleThemeChanged()
 {
-    const auto newColorScheme = platformTheme() ? platformTheme()->colorScheme()
-                                                : Qt::ColorScheme::Unknown;
-    QStyleHintsPrivate::get(QGuiApplication::styleHints())->updateColorScheme(newColorScheme);
-
+    QStyleHintsPrivate::get(QGuiApplication::styleHints())->update(platformTheme());
     updatePalette();
 
     QIconLoader::instance()->updateSystemTheme();

src/gui/kernel/qstylehints.cpp

@@ -1,6 +1,7 @@
 // Copyright (C) 2016 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
+#include "qaccessibilityhints_p.h"
 #include <qstylehints.h>
 #include "qstylehints_p.h"
 #include <qpa/qplatformintegration.h>
@@ -178,6 +179,22 @@ void QStyleHints::setColorScheme(Qt::ColorScheme scheme)
 */
 
 
+/*!
+    \property QStyleHints::accessibility
+    \brief The application's accessibility hints.
+
+    The accessibility hints encapsulates platform dependent accessibility settings
+    such as whether the user wishes the application to be in high contrast or not.
+
+    \sa QAccessibilityHints
+    \since 6.10
+*/
+const QAccessibilityHints *QStyleHints::accessibility() const
+{
+    Q_D(const QStyleHints);
+    return d->accessibilityHints();
+}
+
 /*!
     Sets the \a mousePressAndHoldInterval.
     \internal
@@ -705,6 +722,26 @@ void QStyleHintsPrivate::updateColorScheme(Qt::ColorScheme colorScheme)
     emit q->colorSchemeChanged(colorScheme);
 }
 
+/*!
+    \internal
+
+    Helper function that updates the style hints when the theme changes
+*/
+void QStyleHintsPrivate::update(const QPlatformTheme *theme)
+{
+    Q_ASSERT(theme);
+    updateColorScheme(theme->colorScheme());
+    QAccessibilityHintsPrivate::get(accessibilityHints())->updateContrastPreference(theme->contrastPreference());
+}
+
+QAccessibilityHints *QStyleHintsPrivate::accessibilityHints() const
+{
+    Q_Q(const QStyleHints);
+    if (!m_accessibilityHints)
+        const_cast<QStyleHintsPrivate *>(this)->m_accessibilityHints = new QAccessibilityHints(const_cast<QStyleHints*>(q));
+    return m_accessibilityHints;
+}
+
 QStyleHintsPrivate *QStyleHintsPrivate::get(QStyleHints *q)
 {
     Q_ASSERT(q);

src/gui/kernel/qstylehints.h

@@ -9,9 +9,9 @@
 
 QT_BEGIN_NAMESPACE
 
-
 class QPlatformIntegration;
 class QStyleHintsPrivate;
+class QAccessibilityHints;
 
 class Q_GUI_EXPORT QStyleHints : public QObject
 {
@@ -57,6 +57,7 @@ class Q_GUI_EXPORT QStyleHints : public QObject
     Q_PROPERTY(Qt::ColorScheme colorScheme READ colorScheme WRITE setColorScheme
                RESET unsetColorScheme NOTIFY colorSchemeChanged FINAL)
     Q_PROPERTY(bool menuSelectionWraps READ menuSelectionWraps STORED false CONSTANT FINAL REVISION(6, 10))
+    Q_PROPERTY(const QAccessibilityHints* accessibility READ accessibility CONSTANT FINAL REVISION(6, 10))
 
 public:
     void setMouseDoubleClickInterval(int mouseDoubleClickInterval);
@@ -103,6 +104,7 @@ public:
     Qt::ColorScheme colorScheme() const;
     void setColorScheme(Qt::ColorScheme scheme);
     void unsetColorScheme() { setColorScheme(Qt::ColorScheme::Unknown); }
+    const QAccessibilityHints* accessibility() const;
 
 Q_SIGNALS:
     void cursorFlashTimeChanged(int cursorFlashTime);

src/gui/kernel/qstylehints_p.h

@@ -19,6 +19,7 @@
 #include <QPalette>
 #include <private/qguiapplication_p.h>
 #include "qstylehints.h"
+#include "qaccessibilityhints.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -43,11 +44,15 @@ public:
 
     Qt::ColorScheme colorScheme() const { return m_colorScheme; }
     void updateColorScheme(Qt::ColorScheme colorScheme);
+    void update(const QPlatformTheme *theme);
+
+    QAccessibilityHints *accessibilityHints() const;
 
     static QStyleHintsPrivate *get(QStyleHints *q);
 
 private:
     Qt::ColorScheme m_colorScheme = Qt::ColorScheme::Unknown;
+    QAccessibilityHints* m_accessibilityHints = nullptr;
 };
 
 QT_END_NAMESPACE