Examples: fix touch handling in painting examples

On macOS, we don't deliver a press event for the first press on the
track pad (Qt::WA_TouchPadAcceptSingleTouchEvents is not set by default,
so Qt doesn't deliver a single-press on the track pad as a touch event -
that makes some sense or at least maintains compatibility). Because of
that, point 0 is never added to the finger-mapping hash.

When point 0 is then released, we didn't check if we found a valid
iterator for that point ID, and the example crashed.

Fix this by checking that we have a valid iterator before dereferencing,
and by handling Stationary events in the same way as pressed (add the
point to the mapping if it's not already there).

Pick-to: 6.7 6.6 6.5
Fixes: QTBUG-110266
Change-Id: I32337b801aaabf9b821a97ddc15ad78747b5e6a2
Reviewed-by: Jan Arve Sæther <jan-arve.saether@qt.io>

1 files changed, 6 insertions, 3 deletions

diff --git a/examples/widgets/painting/shared/hoverpoints.cpp b/examples/widgets/painting/shared/hoverpoints.cpp
index 1df6f214ae..a917139613 100644
--- a/examples/widgets/painting/shared/hoverpoints.cpp
+++ b/examples/widgets/painting/shared/hoverpoints.cpp
@@ -127,6 +127,7 @@ bool HoverPoints::eventFilter(QObject *object, QEvent *event)
             const int id = point.id();
             switch (point.state()) {
             case QEventPoint::Pressed:
+            case QEventPoint::Stationary:
             {
                 // find the point, move it
                 const auto mappedPoints = m_fingerPointMapping.values();
@@ -151,7 +152,7 @@ bool HoverPoints::eventFilter(QObject *object, QEvent *event)
                     }
                 }
                 if (activePoint != -1) {
-                    m_fingerPointMapping.insert(point.id(), activePoint);
+                    m_fingerPointMapping.insert(id, activePoint);
                     movePoint(activePoint, point.position());
                 }
             }
@@ -160,8 +161,10 @@ bool HoverPoints::eventFilter(QObject *object, QEvent *event)
             {
                 // move the point and release
                 const auto it = m_fingerPointMapping.constFind(id);
-                movePoint(it.value(), point.position());
-                m_fingerPointMapping.erase(it);
+                if (it != m_fingerPointMapping.constEnd()) {
+                    movePoint(it.value(), point.position());
+                    m_fingerPointMapping.erase(it);
+                }
             }
             break;
             case QEventPoint::Updated: