Merge remote-tracking branch 'origin/tqtc/lts-5.15.5' into tqtc/lts-5.15-opensourcev5.15.5-lts-lgpl

Change-Id: I0cdb390124e783dc9cd832a9954baa76a0e9eb6b

1 files changed, 16 insertions, 7 deletions

diff --git a/src/plugins/platforms/cocoa/qnsview_mouse.mm b/src/plugins/platforms/cocoa/qnsview_mouse.mm
index b42f2d0e7e..8695cfc642 100644
--- a/src/plugins/platforms/cocoa/qnsview_mouse.mm
+++ b/src/plugins/platforms/cocoa/qnsview_mouse.mm
@@ -103,21 +103,14 @@
     if (!m_platformWindow)
         return;
 
-    // get m_buttons in sync
-    // Don't send frme strut events if we are in the middle of a mouse drag.
-    if (m_buttons != Qt::NoButton)
-        return;
-
     switch (theEvent.type) {
     case NSEventTypeLeftMouseDown:
-    case NSEventTypeLeftMouseDragged:
         m_frameStrutButtons |= Qt::LeftButton;
         break;
     case NSEventTypeLeftMouseUp:
          m_frameStrutButtons &= ~Qt::LeftButton;
          break;
     case NSEventTypeRightMouseDown:
-    case NSEventTypeRightMouseDragged:
         m_frameStrutButtons |= Qt::RightButton;
         break;
     case NSEventTypeRightMouseUp:
@@ -132,6 +125,22 @@
         break;
     }
 
+    // m_buttons can sometimes get out of sync with the button state in AppKit
+    // E.g if the QNSView where a drag starts is reparented to another window
+    // while the drag is ongoing, it will not get the corresponding mouseUp
+    // call. This will result in m_buttons to be stuck on Qt::LeftButton.
+    // Since we know which buttons was pressed/released directly on the frame
+    // strut, we can rectify m_buttons here so that we at least don't return early
+    // from the drag test underneath because of the faulty m_buttons state.
+    // FIXME: get m_buttons in sync with AppKit/NSEvent all over in QNSView.
+    m_buttons &= ~m_frameStrutButtons;
+
+    if (m_buttons != Qt::NoButton) {
+        // Don't send frame strut events if we are in the middle of
+        // a mouse drag that didn't start on the frame strut.
+        return;
+    }
+
     NSWindow *window = [self window];
     NSPoint windowPoint = [theEvent locationInWindow];