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>

1 files changed, 13 insertions, 4 deletions

diff --git a/src/plugins/platforms/windows/qwindowsmousehandler.cpp b/src/plugins/platforms/windows/qwindowsmousehandler.cpp
index e6b80f2b93..e83354157b 100644
--- a/src/plugins/platforms/windows/qwindowsmousehandler.cpp
+++ b/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) {