Windows: Delay-initialize pluggable touch devices.

Move touch device initialization code to QWindowsContext and
replace the assert on the touch device in QWindowsMouseHandler
by a call to the initTouch().

Task-number: QTBUG-48849
Change-Id: If8573b8283ef94e7fd015f6edc626e3c8cc0b139
Reviewed-by: Joni Poikelin <joni.poikelin@theqtcompany.com>
Reviewed-by: Oliver Wolff <oliver.wolff@theqtcompany.com>
Reviewed-by: Andreas Holzammer <andreas.holzammer@kdab.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -33,6 +33,7 @@
 ****************************************************************************/
 
 #include "qwindowscontext.h"
+#include "qwindowsintegration.h"
 #include "qwindowswindow.h"
 #include "qwindowskeymapper.h"
 #include "qwindowsguieventdispatcher.h"
@@ -201,12 +202,14 @@ void QWindowsUser32DLL::init()
 
 bool QWindowsUser32DLL::initTouch()
 {
-    QSystemLibrary library(QStringLiteral("user32"));
-    isTouchWindow = (IsTouchWindow)(library.resolve("IsTouchWindow"));
-    registerTouchWindow = (RegisterTouchWindow)(library.resolve("RegisterTouchWindow"));
-    unregisterTouchWindow = (UnregisterTouchWindow)(library.resolve("UnregisterTouchWindow"));
-    getTouchInputInfo = (GetTouchInputInfo)(library.resolve("GetTouchInputInfo"));
-    closeTouchInputHandle = (CloseTouchInputHandle)(library.resolve("CloseTouchInputHandle"));
+    if (!isTouchWindow && QSysInfo::windowsVersion() >= QSysInfo::WV_WINDOWS7) {
+        QSystemLibrary library(QStringLiteral("user32"));
+        isTouchWindow = (IsTouchWindow)(library.resolve("IsTouchWindow"));
+        registerTouchWindow = (RegisterTouchWindow)(library.resolve("RegisterTouchWindow"));
+        unregisterTouchWindow = (UnregisterTouchWindow)(library.resolve("UnregisterTouchWindow"));
+        getTouchInputInfo = (GetTouchInputInfo)(library.resolve("GetTouchInputInfo"));
+        closeTouchInputHandle = (CloseTouchInputHandle)(library.resolve("CloseTouchInputHandle"));
+    }
     return isTouchWindow && registerTouchWindow && unregisterTouchWindow && getTouchInputInfo && closeTouchInputHandle;
 }
 
@@ -359,6 +362,36 @@ QWindowsContext::~QWindowsContext()
     m_instance = 0;
 }
 
+bool QWindowsContext::initTouch()
+{
+    return initTouch(QWindowsIntegration::instance()->options());
+}
+
+bool QWindowsContext::initTouch(unsigned integrationOptions)
+{
+    if (d->m_systemInfo & QWindowsContext::SI_SupportsTouch)
+        return true;
+
+    QTouchDevice *touchDevice = d->m_mouseHandler.ensureTouchDevice();
+    if (!touchDevice)
+        return false;
+
+#ifndef Q_OS_WINCE
+    if (!QWindowsContext::user32dll.initTouch()) {
+        delete touchDevice;
+        return false;
+    }
+#endif // !Q_OS_WINCE
+
+    if (!(integrationOptions & QWindowsIntegration::DontPassOsMouseEventsSynthesizedFromTouch))
+        touchDevice->setCapabilities(touchDevice->capabilities() | QTouchDevice::MouseEmulation);
+
+    QWindowSystemInterface::registerTouchDevice(touchDevice);
+
+    d->m_systemInfo |= QWindowsContext::SI_SupportsTouch;
+    return true;
+}
+
 void QWindowsContext::setTabletAbsoluteRange(int a)
 {
 #if !defined(QT_NO_TABLETEVENT) && !defined(Q_OS_WINCE)

src/plugins/platforms/windows/qwindowscontext.h

@@ -170,6 +170,9 @@ public:
     explicit QWindowsContext();
     ~QWindowsContext();
 
+    bool initTouch();
+    bool initTouch(unsigned integrationOptions); // For calls from QWindowsIntegration::QWindowsIntegration() only.
+
     int defaultDPI() const;
 
     QString registerWindowClass(const QWindow *w);

src/plugins/platforms/windows/qwindowsintegration.cpp

@@ -230,17 +230,7 @@ QWindowsIntegrationPrivate::QWindowsIntegrationPrivate(const QStringList &paramL
         << __FUNCTION__ << "DpiAwareness=" << dpiAwareness <<",Scaling="
         << QWindowsScaling::factor();
 
-    QTouchDevice *touchDevice = m_context.touchDevice();
-    if (touchDevice) {
-#ifdef Q_OS_WINCE
-        touchDevice->setCapabilities(touchDevice->capabilities() | QTouchDevice::MouseEmulation);
-#else
-        if (!(m_options & QWindowsIntegration::DontPassOsMouseEventsSynthesizedFromTouch)) {
-            touchDevice->setCapabilities(touchDevice->capabilities() | QTouchDevice::MouseEmulation);
-        }
-#endif
-        QWindowSystemInterface::registerTouchDevice(touchDevice);
-    }
+    m_context.initTouch(m_options);
 }
 
 QWindowsIntegrationPrivate::~QWindowsIntegrationPrivate()

src/plugins/platforms/windows/qwindowsmousehandler.cpp

@@ -150,12 +150,19 @@ static inline QTouchDevice *createTouchDevice()
 QWindowsMouseHandler::QWindowsMouseHandler() :
     m_windowUnderMouse(0),
     m_trackedWindow(0),
-    m_touchDevice(createTouchDevice()),
+    m_touchDevice(Q_NULLPTR),
     m_leftButtonDown(false),
     m_previousCaptureWindow(0)
 {
 }
 
+QTouchDevice *QWindowsMouseHandler::ensureTouchDevice()
+{
+    if (!m_touchDevice)
+        m_touchDevice = createTouchDevice();
+    return m_touchDevice;
+}
+
 Qt::MouseButtons QWindowsMouseHandler::queryMouseButtons()
 {
     Qt::MouseButtons result = 0;
@@ -480,7 +487,11 @@ bool QWindowsMouseHandler::translateTouchEvent(QWindow *window, HWND,
     typedef QWindowSystemInterface::TouchPoint QTouchPoint;
     typedef QList<QWindowSystemInterface::TouchPoint> QTouchPointList;
 
-    Q_ASSERT(m_touchDevice);
+    if (!QWindowsContext::instance()->initTouch()) {
+        qWarning("Unable to initialize touch handling.");
+        return true;
+    }
+
     const QRect screenGeometry = window->screen()->geometry();
 
     const int winTouchPointCount = msg.wParam;
@@ -491,8 +502,6 @@ bool QWindowsMouseHandler::translateTouchEvent(QWindow *window, HWND,
     touchPoints.reserve(winTouchPointCount);
     Qt::TouchPointStates allStates = 0;
 
-    Q_ASSERT(QWindowsContext::user32dll.getTouchInputInfo);
-
     QWindowsContext::user32dll.getTouchInputInfo((HANDLE) msg.lParam, msg.wParam, winTouchInputs.data(), sizeof(TOUCHINPUT));
     const qreal screenPosFactor = 0.01 / qreal(QWindowsScaling::factor());
     for (int i = 0; i < winTouchPointCount; ++i) {

src/plugins/platforms/windows/qwindowsmousehandler.h

@@ -52,6 +52,7 @@ public:
     QWindowsMouseHandler();
 
     QTouchDevice *touchDevice() const { return m_touchDevice; }
+    QTouchDevice *ensureTouchDevice();
 
     bool translateMouseEvent(QWindow *widget, HWND hwnd,
                              QtWindows::WindowsEventType t, MSG msg,