Windows: Provide a way to switch between WinTab and Windows Ink at run-time

This change adds the setWinTabEnabled() function to Qt Platform Headers,
which allows an application to set at run-time whether the WinTab API will
be used for tablet input instead of the native Windows Ink API.

[ChangeLog][Windows] The setWinTabEnabled() function added to Qt Platform
Headers now allows an application to set at run-time whether the WinTab API
will be used for tablet input instead of the native Windows Ink API.

Fixes: QTBUG-83218
Change-Id: I51d3c7316baeda136763cf37c2f54295905450ec
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

src/platformheaders/windowsfunctions/qwindowswindowfunctions.h

@@ -108,6 +108,14 @@ public:
         IsTabletModeType func = reinterpret_cast<IsTabletModeType>(QGuiApplication::platformFunction(isTabletModeIdentifier()));
         return func && func();
     }
+
+    typedef bool (*SetWinTabEnabled)(bool enabled);
+    static const QByteArray setWinTabEnabledIdentifier() { return QByteArrayLiteral("WindowsSetWinTabEnabled"); }
+    static bool setWinTabEnabled(bool enabled)
+    {
+        SetWinTabEnabled func = reinterpret_cast<SetWinTabEnabled>(QGuiApplication::platformFunction(setWinTabEnabledIdentifier()));
+        return func && func(enabled);
+    }
 };
 
 Q_DECLARE_OPERATORS_FOR_FLAGS(QWindowsWindowFunctions::TouchWindowTouchTypes)

src/platformheaders/windowsfunctions/qwindowswindowfunctions.qdoc

@@ -210,3 +210,30 @@
     \sa QWidget::showMaximized(), QWidget::saveGeometry(), QWidget::restoreGeometry()
     \since 5.9
 */
+
+/*!
+    \typedef QWindowsWindowFunctions::SetWinTabEnabled
+    \since 6.0
+
+    This is the typedef for the function returned by QGuiApplication::platformFunction
+    when passed setWinTabEnabledIdentifier().
+*/
+
+/*!
+    \fn QByteArray QWindowsWindowFunctions::setWinTabEnabledIdentifier()
+    \since 6.0
+
+    This function returns the bytearray that can be used to query
+    QGuiApplication::platformFunction to retrieve the SetWinTabEnabled function.
+*/
+
+/*!
+    \fn bool QWindowsWindowFunctions::setWinTabEnabled(bool enabled)
+    \since 6.0
+
+    This is a convenience function that can be used directly instead of resolving
+    the function pointer.
+
+    \a enabled determines whether the WinTab API will be used for tablet input instead
+    of the native API. Returns true if the operation was successful.
+*/

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -380,6 +380,16 @@ bool QWindowsContext::initTablet(unsigned integrationOptions)
 #endif
 }
 
+bool QWindowsContext::disposeTablet()
+{
+#if QT_CONFIG(tabletevent)
+    d->m_tabletSupport.reset();
+    return true;
+#else
+    return false;
+#endif
+}
+
 bool QWindowsContext::initPointer(unsigned integrationOptions)
 {
     if (integrationOptions & QWindowsIntegration::DontUseWMPointer)

src/plugins/platforms/windows/qwindowscontext.h

@@ -175,6 +175,7 @@ public:
     bool initTouch(unsigned integrationOptions); // For calls from QWindowsIntegration::QWindowsIntegration() only.
     bool initTablet(unsigned integrationOptions);
     bool initPointer(unsigned integrationOptions);
+    bool disposeTablet();
 
     bool initPowerNotificationHandler();
 

src/plugins/platforms/windows/qwindowsintegration.cpp

@@ -140,6 +140,7 @@ struct QWindowsIntegrationPrivate
     ~QWindowsIntegrationPrivate();
 
     unsigned m_options = 0;
+    int m_tabletAbsoluteRange = -1;
     QWindowsContext m_context;
     QPlatformFontDatabase *m_fontDatabase = nullptr;
 #if QT_CONFIG(clipboard)
@@ -239,19 +240,18 @@ QWindowsIntegrationPrivate::QWindowsIntegrationPrivate(const QStringList &paramL
     initOpenGlBlacklistResources();
 
     static bool dpiAwarenessSet = false;
-    int tabletAbsoluteRange = -1;
     // Default to per-monitor awareness to avoid being scaled when monitors with different DPI
     // are connected to Windows 8.1
     QtWindows::ProcessDpiAwareness dpiAwareness = QtWindows::ProcessPerMonitorDpiAware;
-    m_options = parseOptions(paramList, &tabletAbsoluteRange, &dpiAwareness);
+    m_options = parseOptions(paramList, &m_tabletAbsoluteRange, &dpiAwareness);
     QWindowsFontDatabase::setFontOptions(m_options);
 
     if (m_context.initPointer(m_options)) {
         QCoreApplication::setAttribute(Qt::AA_CompressHighFrequencyEvents);
     } else {
         m_context.initTablet(m_options);
-        if (tabletAbsoluteRange >= 0)
-            m_context.setTabletAbsoluteRange(tabletAbsoluteRange);
+        if (m_tabletAbsoluteRange >= 0)
+            m_context.setTabletAbsoluteRange(m_tabletAbsoluteRange);
     }
 
     if (!dpiAwarenessSet) { // Set only once in case of repeated instantiations of QGuiApplication.
@@ -642,6 +642,28 @@ void QWindowsIntegration::beep() const
     MessageBeep(MB_OK);  // For QApplication
 }
 
+bool QWindowsIntegration::setWinTabEnabled(bool enabled)
+{
+    bool ret = false;
+    if (QWindowsIntegration *p = QWindowsIntegration::instance()) {
+        if (enabled) {
+            if (p->d->m_context.tabletSupport()) {
+                ret = true;
+            } else {
+                ret = p->d->m_context.initTablet(p->d->m_options);
+                if (ret && p->d->m_tabletAbsoluteRange >= 0)
+                    p->d->m_context.setTabletAbsoluteRange(p->d->m_tabletAbsoluteRange);
+            }
+        } else {
+            if (p->d->m_context.tabletSupport())
+                ret = p->d->m_context.disposeTablet();
+            else
+                ret = true;
+        }
+    }
+    return ret;
+}
+
 #if QT_CONFIG(vulkan)
 QPlatformVulkanInstance *QWindowsIntegration::createPlatformVulkanInstance(QVulkanInstance *instance) const
 {

src/plugins/platforms/windows/qwindowsintegration.h

@@ -111,6 +111,8 @@ public:
 
     static QWindowsIntegration *instance() { return m_instance; }
 
+    static bool setWinTabEnabled(bool enabled);
+
     unsigned options() const;
 
     void beep() const override;

src/plugins/platforms/windows/qwindowsnativeinterface.cpp

@@ -300,6 +300,8 @@ QFunctionPointer QWindowsNativeInterface::platformFunction(const QByteArray &fun
         return QFunctionPointer(QWindowsNativeInterface::setWindowActivationBehavior);
     if (function == QWindowsWindowFunctions::isTabletModeIdentifier())
         return QFunctionPointer(QWindowsNativeInterface::isTabletMode);
+    if (function == QWindowsWindowFunctions::setWinTabEnabledIdentifier())
+        return QFunctionPointer(QWindowsIntegration::setWinTabEnabled);
     return nullptr;
 }