Handle the case where TOUCHINPUT id numbers are not reused

As documented in the Windows 7 SDK RC, the id's may not be reused. We
don't want the touchInputIDToTouchPointID hash to grow indefinitely, so
clear it each time we detect that all touch points have been released.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/gui/kernel/qapplication_win.cpp b/src/gui/kernel/qapplication_win.cpp
index 66dfee2..f8b1cbb 100644
--- a/src/gui/kernel/qapplication_win.cpp
+++ b/src/gui/kernel/qapplication_win.cpp
@@ -4027,6 +4027,7 @@ bool QApplicationPrivate::translateTouchEvent(const MSG &msg)
 
     QVector<TOUCHINPUT> winTouchInputs(msg.wParam);
     memset(winTouchInputs.data(), 0, sizeof(TOUCHINPUT) * winTouchInputs.count());
+    Qt::TouchPointStates allStates = 0;
     QApplicationPrivate::GetTouchInputInfo((HANDLE) msg.lParam, msg.wParam, winTouchInputs.data(), sizeof(TOUCHINPUT));
     for (int i = 0; i < winTouchInputs.count(); ++i) {
         const TOUCHINPUT &touchInput = winTouchInputs.at(i);
@@ -4062,10 +4063,17 @@ bool QApplicationPrivate::translateTouchEvent(const MSG &msg)
         touchPoint.setState(state);
         touchPoint.setScreenRect(screenRect);
 
+        allStates |= state;
+
         touchPoints.append(touchPoint);
     }
     QApplicationPrivate::CloseTouchInputHandle((HANDLE) msg.lParam);
 
+    if ((allStates & Qt::TouchPointStateMask) == Qt::TouchPointReleased) {
+        // all touch points released, forget the ids we've seen, they may not be reused
+        touchInputIDToTouchPointID.clear();
+    }
+
     translateRawTouchEvent(widgetForHwnd, touchPoints);
     return true;
 }