Propagate appearance property from QPlatformTheme to QStyleHints

Implement appearance property, getter and notifier in QStyleHints.

Update appearance property in QStyleHints when handling theme
change in QGuiApplicationPrivate.

Task-number: QTBUG-106381
Change-Id: Idd67ca9df248ec9d9e67c0d48121e8eead11a9e2
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/gui/CMakeLists.txt

@@ -132,7 +132,7 @@ qt_internal_add_module(Gui
         kernel/qrasterwindow.cpp kernel/qrasterwindow.h
         kernel/qscreen.cpp kernel/qscreen.h kernel/qscreen_p.h
         kernel/qsessionmanager.cpp kernel/qsessionmanager.h kernel/qsessionmanager_p.h
-        kernel/qstylehints.cpp kernel/qstylehints.h
+        kernel/qstylehints.cpp kernel/qstylehints.h kernel/qstylehints_p.h
         kernel/qsurface.cpp kernel/qsurface.h
         kernel/qsurfaceformat.cpp kernel/qsurfaceformat.h
         kernel/qtestsupport_gui.cpp kernel/qtestsupport_gui.h

src/gui/kernel/qguiapplication.cpp

@@ -41,6 +41,7 @@
 
 #include <QtGui/qgenericpluginfactory.h>
 #include <QtGui/qstylehints.h>
+#include <QtGui/private/qstylehints_p.h>
 #include <QtGui/qinputmethod.h>
 #include <QtGui/qpixmapcache.h>
 #include <qpa/qplatforminputcontext.h>
@@ -2553,6 +2554,21 @@ void QGuiApplicationPrivate::processThemeChanged(QWindowSystemInterfacePrivate::
     const QWindowList windows = tce->window ? QWindowList{tce->window} : window_list;
     for (auto *window : windows)
         QGuiApplication::sendSpontaneousEvent(window, &themeChangeEvent);
+
+    QStyleHintsPrivate::get(QGuiApplication::styleHints())->setAppearance(appearance());
+}
+
+/*!
+   \internal
+   \brief QGuiApplicationPrivate::appearance
+   \return the platform theme's appearance
+   or Qt::Appearance::Unknown if a platform theme cannot be established
+   Qt::Appearance.
+ */
+Qt::Appearance QGuiApplicationPrivate::appearance()
+{
+    return platformTheme() ? platformTheme()->appearance()
+                           : Qt::Appearance::Unknown;
 }
 
 void QGuiApplicationPrivate::handleThemeChanged()

src/gui/kernel/qguiapplication_p.h

@@ -313,6 +313,8 @@ private:
 
     friend class QDragManager;
 
+    static Qt::Appearance appearance();
+
     static QGuiApplicationPrivate *self;
     static int m_fakeMouseSourcePointId;
 #ifdef Q_OS_WIN

src/gui/kernel/qstylehints.cpp

@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
 #include <qstylehints.h>
+#include "qstylehints_p.h"
 #include <qpa/qplatformintegration.h>
 #include <qpa/qplatformtheme.h>
 #include <private/qguiapplication_p.h>
@@ -43,25 +44,6 @@ static inline QVariant themeableHint(QPlatformTheme::ThemeHint th)
     return QPlatformTheme::defaultThemeHint(th);
 }
 
-class QStyleHintsPrivate : public QObjectPrivate
-{
-    Q_DECLARE_PUBLIC(QStyleHints)
-public:
-    int m_mouseDoubleClickInterval = -1;
-    int m_mousePressAndHoldInterval = -1;
-    int m_startDragDistance = -1;
-    int m_startDragTime = -1;
-    int m_keyboardInputInterval = -1;
-    int m_cursorFlashTime = -1;
-    int m_tabFocusBehavior = -1;
-    int m_uiEffects = -1;
-    int m_showShortcutsInContextMenus = -1;
-    int m_wheelScrollLines = -1;
-    int m_mouseQuickSelectionThreshold = -1;
-    int m_mouseDoubleClickDistance = -1;
-    int m_touchDoubleTapDistance = -1;
-};
-
 /*!
     \class QStyleHints
     \since 5.0
@@ -139,6 +121,17 @@ int QStyleHints::touchDoubleTapDistance() const
                 themeableHint(QPlatformTheme::TouchDoubleTapDistance).toInt();
 }
 
+/*!
+    \property QStyleHints::appearance
+    \brief the appearance of the platform theme
+    \sa Qt::Appearance
+    \since 6.5
+*/
+Qt::Appearance QStyleHints::appearance() const
+{
+    return d_func()->appearance();
+}
+
 /*!
     Sets the \a mousePressAndHoldInterval.
     \internal
@@ -583,6 +576,26 @@ int QStyleHints::mouseQuickSelectionThreshold() const
     return themeableHint(QPlatformTheme::MouseQuickSelectionThreshold, QPlatformIntegration::MouseQuickSelectionThreshold).toInt();
 }
 
+/*!
+   \internal
+   QStyleHintsPrivate::setAppearance - set a new appearance.
+   Set \a appearance as the new appearance of the QStyleHints.
+   The appearanceChanged signal will be emitted if present and new appearance differ.
+ */
+void QStyleHintsPrivate::setAppearance(Qt::Appearance appearance)
+{
+    if (m_appearance != appearance) {
+        m_appearance = appearance;
+        emit q_func()->appearanceChanged(appearance);
+    }
+}
+
+QStyleHintsPrivate *QStyleHintsPrivate::get(QStyleHints *q)
+{
+    Q_ASSERT(q);
+    return q->d_func();
+}
+
 QT_END_NAMESPACE
 
 #include "moc_qstylehints.cpp"

src/gui/kernel/qstylehints.h

@@ -49,6 +49,7 @@ class Q_GUI_EXPORT QStyleHints : public QObject
     Q_PROPERTY(int mouseDoubleClickDistance READ mouseDoubleClickDistance STORED false CONSTANT
                FINAL)
     Q_PROPERTY(int touchDoubleTapDistance READ touchDoubleTapDistance STORED false CONSTANT FINAL)
+    Q_PROPERTY(Qt::Appearance appearance READ appearance NOTIFY appearanceChanged FINAL)
 
 public:
     void setMouseDoubleClickInterval(int mouseDoubleClickInterval);
@@ -85,6 +86,7 @@ public:
     void setWheelScrollLines(int scrollLines);
     void setMouseQuickSelectionThreshold(int threshold);
     int mouseQuickSelectionThreshold() const;
+    Qt::Appearance appearance() const;
 
 Q_SIGNALS:
     void cursorFlashTimeChanged(int cursorFlashTime);
@@ -98,6 +100,7 @@ Q_SIGNALS:
     void showShortcutsInContextMenusChanged(bool);
     void wheelScrollLinesChanged(int scrollLines);
     void mouseQuickSelectionThresholdChanged(int threshold);
+    void appearanceChanged(Qt::Appearance appearance);
 
 private:
     friend class QGuiApplication;

src/gui/kernel/qstylehints_p.h

@@ -0,0 +1,53 @@
+// Copyright (C) 2022 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 QSTYLEHINTS_P_H
+#define QSTYLEHINTS_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 <qpa/qplatformintegration.h>
+#include <QPalette>
+#include <private/qguiapplication_p.h>
+#include "qstylehints.h"
+
+QT_BEGIN_NAMESPACE
+
+class QStyleHintsPrivate : public QObjectPrivate
+{
+    Q_DECLARE_PUBLIC(QStyleHints)
+public:
+    int m_mouseDoubleClickInterval = -1;
+    int m_mousePressAndHoldInterval = -1;
+    int m_startDragDistance = -1;
+    int m_startDragTime = -1;
+    int m_keyboardInputInterval = -1;
+    int m_cursorFlashTime = -1;
+    int m_tabFocusBehavior = -1;
+    int m_uiEffects = -1;
+    int m_showShortcutsInContextMenus = -1;
+    int m_wheelScrollLines = -1;
+    int m_mouseQuickSelectionThreshold = -1;
+    int m_mouseDoubleClickDistance = -1;
+    int m_touchDoubleTapDistance = -1;
+
+    Qt::Appearance appearance() const { return m_appearance; };
+    void setAppearance(Qt::Appearance appearance);
+    static QStyleHintsPrivate *get(QStyleHints *q);
+
+private:
+    Qt::Appearance m_appearance = Qt::Appearance::Unknown;
+};
+
+QT_END_NAMESPACE
+
+#endif