Windows platform headers: Add isTabletMode()

Add a bool function querying Windows 10 tablet mode.

Task-number: QTBUG-56831
Change-Id: Ief728a7d80a11ba79f7859033ff4be6ef79bbd4e
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

src/platformheaders/windowsfunctions/qwindowswindowfunctions.h

@@ -90,6 +90,15 @@ public:
         if (func)
             func(behavior);
     }
+
+    typedef bool (*IsTabletModeType)();
+    static const QByteArray isTabletModeIdentifier() { return QByteArrayLiteral("WindowsIsTabletMode"); }
+
+    static bool isTabletMode()
+    {
+        IsTabletModeType func = reinterpret_cast<IsTabletModeType>(QGuiApplication::platformFunction(isTabletModeIdentifier()));
+        return func && func();
+    }
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(QWindowsWindowFunctions::TouchWindowTouchTypes)

src/platformheaders/windowsfunctions/qwindowswindowfunctions.qdoc

@@ -144,3 +144,35 @@
     \sa QWidget::activateWindow(), QWindow::requestActivate()
     \since 5.7
 */
+
+/*!
+    \typedef QWindowsWindowFunctions::IsTabletModeType
+
+    This is the typedef for the function returned by QGuiApplication::platformFunction()
+    when passed isTabletModeIdentifier().
+
+    \since 5.9
+*/
+
+/*!
+    \fn QByteArray QWindowsWindowFunctions::isTabletModeIdentifier()
+
+    Returns a bytearray that can be used to query
+    QGuiApplication::platformFunction() to retrieve the IsTabletModeType
+    function.
+
+    \since 5.9
+*/
+
+/*!
+    \fn bool QWindowsWindowFunctions::isTabletMode()
+
+    This is a convenience function that can be used directly instead of resolving
+    the function pointer. The function can be used to query whether Windows 10
+    operates in \e{Tablet Mode}. In this mode, Windows forces all application
+    main windows to open in maximized state. Applications should then avoid
+    resizing windows or restoring geometries to non-maximized states.
+
+    \sa QWidget::showMaximized(), QWidget::saveGeometry(), QWidget::restoreGeometry()
+    \since 5.9
+*/

src/plugins/platforms/windows/qwindowsnativeinterface.cpp

@@ -38,6 +38,7 @@
 ****************************************************************************/
 
 #include "qwindowsnativeinterface.h"
+#include "qwindowsclipboard.h"
 #include "qwindowswindow.h"
 #include "qwindowscontext.h"
 #include "qwindowscursor.h"
@@ -45,6 +46,7 @@
 #include "qwindowsopengltester.h"
 #include "qwindowsintegration.h"
 #include "qwindowsmime.h"
+#include "qwin10helpers.h"
 
 #include <QtGui/QWindow>
 #include <QtGui/QOpenGLContext>
@@ -253,14 +255,23 @@ QFont QWindowsNativeInterface::logFontToQFont(const void *logFont, int verticalD
     return QWindowsFontDatabase::LOGFONT_to_QFont(*reinterpret_cast<const LOGFONT *>(logFont), verticalDpi);
 }
 
+bool QWindowsNativeInterface::isTabletMode()
+{
+#if QT_CONFIG(clipboard)
+    if (const QWindowsClipboard *clipboard = QWindowsClipboard::instance())
+        return qt_windowsIsTabletMode(clipboard->clipboardViewer());
+#endif
+    return false;
+}
+
 QFunctionPointer QWindowsNativeInterface::platformFunction(const QByteArray &function) const
 {
     if (function == QWindowsWindowFunctions::setTouchWindowTouchTypeIdentifier())
         return QFunctionPointer(QWindowsWindow::setTouchWindowTouchTypeStatic);
     else if (function == QWindowsWindowFunctions::setHasBorderInFullScreenIdentifier())
         return QFunctionPointer(QWindowsWindow::setHasBorderInFullScreenStatic);
-    else if (function == QWindowsWindowFunctions::setWindowActivationBehaviorIdentifier())
-        return QFunctionPointer(QWindowsNativeInterface::setWindowActivationBehavior);
+    else if (function == QWindowsWindowFunctions::isTabletModeIdentifier())
+        return QFunctionPointer(QWindowsNativeInterface::isTabletMode);
     return Q_NULLPTR;
 }
 

src/plugins/platforms/windows/qwindowsnativeinterface.h

@@ -102,6 +102,8 @@ public:
     static void setWindowActivationBehavior(QWindowsWindowFunctions::WindowActivationBehavior b)
         { QWindowsNativeInterface::m_windowActivationBehavior = b; }
 
+    static bool isTabletMode();
+
     QFunctionPointer platformFunction(const QByteArray &function) const override;
 
 private: