From 59be0509e087a5d4a8884a56e14a2ddbf5735ac4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tor=20Arne=20Vestb=C3=B8?= <tor.arne.vestbo@digia.com>
Date: Thu, 7 Nov 2013 13:15:31 +0100
Subject: [PATCH] iOS: Detect/handle cancellation of subset of touch points

Change-Id: I0d345d07fe62a8c7844333bf1eed9be6d6fa432f
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>
---
 src/plugins/platforms/ios/qioswindow.mm | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/plugins/platforms/ios/qioswindow.mm b/src/plugins/platforms/ios/qioswindow.mm
index 2cb3fe86e1..70f4cc4267 100644
--- a/src/plugins/platforms/ios/qioswindow.mm
+++ b/src/plugins/platforms/ios/qioswindow.mm
@@ -226,10 +226,16 @@
 
 - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
 {
-    Q_UNUSED(touches) // ### can a subset of the active touches be cancelled?
+    if (!touches) {
+        m_activeTouches.clear();
+    } else {
+        for (UITouch *touch in touches)
+            m_activeTouches.remove(touch);
+
+        Q_ASSERT_X(m_activeTouches.isEmpty(), Q_FUNC_INFO,
+            "Subset of active touches cancelled by UIKit");
+    }
 
-    // Clear current touch points
-    m_activeTouches.clear();
     m_nextTouchId = 0;
 
     // Send cancel touch event synchronously