Windows: Only set the touch flags if the window is not already registered

It is possible for there to be a HCBT_CREATEWND hook which can set the
touch window flags already while the window is being created. Therefore
we want to defer to those settings instead as they should take precedence.

Change-Id: If8dcbd34db2b3bbbfb1bc36731665fb17fb87c24
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>

3 files changed, 11 insertions, 2 deletions

diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index ebd41d482b..fa355f6201 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -173,7 +173,7 @@ static inline QWindowsSessionManager *platformSessionManager() {
 QWindowsUser32DLL::QWindowsUser32DLL() :
     setLayeredWindowAttributes(0), updateLayeredWindow(0),
     updateLayeredWindowIndirect(0),
-    isHungAppWindow(0),
+    isHungAppWindow(0), isTouchWindow(0),
     registerTouchWindow(0), unregisterTouchWindow(0),
     getTouchInputInfo(0), closeTouchInputHandle(0), setProcessDPIAware(0),
     addClipboardFormatListener(0), removeClipboardFormatListener(0)
@@ -202,11 +202,12 @@ 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"));
-    return registerTouchWindow && unregisterTouchWindow && getTouchInputInfo && closeTouchInputHandle;
+    return isTouchWindow && registerTouchWindow && unregisterTouchWindow && getTouchInputInfo && closeTouchInputHandle;
 }
 
 /*!
diff --git a/src/plugins/platforms/windows/qwindowscontext.h b/src/plugins/platforms/windows/qwindowscontext.h
index 870a42946d..81f4a36433 100644
--- a/src/plugins/platforms/windows/qwindowscontext.h
+++ b/src/plugins/platforms/windows/qwindowscontext.h
@@ -76,6 +76,7 @@ struct QWindowsUser32DLL
     inline void init();
     inline bool initTouch();
 
+    typedef BOOL (WINAPI *IsTouchWindow)(HWND, PULONG);
     typedef BOOL (WINAPI *RegisterTouchWindow)(HWND, ULONG);
     typedef BOOL (WINAPI *UnregisterTouchWindow)(HWND);
     typedef BOOL (WINAPI *GetTouchInputInfo)(HANDLE, UINT, PVOID, int);
@@ -99,6 +100,7 @@ struct QWindowsUser32DLL
     IsHungAppWindow isHungAppWindow;
 
     // Touch functions from Windows 7 onwards (also for use with Q_CC_MSVC).
+    IsTouchWindow isTouchWindow;
     RegisterTouchWindow registerTouchWindow;
     UnregisterTouchWindow unregisterTouchWindow;
     GetTouchInputInfo getTouchInputInfo;
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index 4cf8fcf4da..6b490b9404 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -2294,6 +2294,12 @@ void QWindowsWindow::registerTouchWindow(QWindowsWindowFunctions::TouchWindowTou
 #ifndef Q_OS_WINCE
     if ((QWindowsContext::instance()->systemInfo() & QWindowsContext::SI_SupportsTouch)
         && window()->type() != Qt::ForeignWindow) {
+        ULONG touchFlags = 0;
+        const bool ret = QWindowsContext::user32dll.isTouchWindow(m_data.hwnd, &touchFlags);
+        // Return if it is not a touch window or the flags are already set by a hook
+        // such as HCBT_CREATEWND
+        if (!ret || touchFlags != 0)
+            return;
         if (QWindowsContext::user32dll.registerTouchWindow(m_data.hwnd, (ULONG)touchTypes))
             setFlag(TouchRegistered);
         else