Shared node bookkeeping

Any time a property references a QNode there is a risk that the node gets
destroyed and then the property is left pointing to a dangling pointer.

To handle such cases, setters of such properties are able to use a helper
that internally connect QObject::destroyed signal to a setter removal method.

Change-Id: I42428c851d0e3d2d88ab0cf6a5b75605334ec648
Task-number: QTBUG-53456
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

8 files changed, 63 insertions, 0 deletions

diff --git a/src/input/frontend/qabstractaxisinput.cpp b/src/input/frontend/qabstractaxisinput.cpp
index 77966eb1d..ff7c69c12 100644
--- a/src/input/frontend/qabstractaxisinput.cpp
+++ b/src/input/frontend/qabstractaxisinput.cpp
@@ -73,10 +73,21 @@ void QAbstractAxisInput::setSourceDevice(QAbstractPhysicalDevice *sourceDevice)
     Q_D(QAbstractAxisInput);
     if (d->m_sourceDevice != sourceDevice) {
 
+        if (d->m_sourceDevice)
+            d->unregisterDestructionHelper(d->m_sourceDevice);
+
+        // We need to add it as a child of the current node if it has been declared inline
+        // Or not previously added as a child of the current node so that
+        // 1) The backend gets notified about it's creation
+        // 2) When the current node is destroyed, it gets destroyed as well
         if (sourceDevice && !sourceDevice->parent())
             sourceDevice->setParent(this);
 
         d->m_sourceDevice = sourceDevice;
+        // Ensures proper bookkeeping
+        if (d->m_sourceDevice)
+            d->registerDestructionHelper(sourceDevice, &QAbstractAxisInput::setSourceDevice, d->m_sourceDevice);
+
         emit sourceDeviceChanged(sourceDevice);
     }
 }
diff --git a/src/input/frontend/qaction.cpp b/src/input/frontend/qaction.cpp
index 11a8d3ab6..2d98cc9e8 100644
--- a/src/input/frontend/qaction.cpp
+++ b/src/input/frontend/qaction.cpp
@@ -125,6 +125,9 @@ void QAction::addInput(QAbstractActionInput *input)
         if (!input->parent())
             input->setParent(this);
 
+        // Ensures proper bookkeeping
+        d->registerDestructionHelper(input, &QAction::removeInput, d->m_inputs);
+
         if (d->m_changeArbiter != nullptr) {
             const auto change = Qt3DCore::QPropertyNodeAddedChangePtr::create(id(), input);
             change->setPropertyName("input");
@@ -148,6 +151,9 @@ void QAction::removeInput(QAbstractActionInput *input)
         }
 
         d->m_inputs.removeOne(input);
+
+        // Remove bookkeeping connection
+        d->unregisterDestructionHelper(input);
     }
 }
 
diff --git a/src/input/frontend/qactioninput.cpp b/src/input/frontend/qactioninput.cpp
index d3441d284..0be75ec07 100644
--- a/src/input/frontend/qactioninput.cpp
+++ b/src/input/frontend/qactioninput.cpp
@@ -137,12 +137,20 @@ void QActionInput::setSourceDevice(QAbstractPhysicalDevice *sourceDevice)
     Q_D(QActionInput);
     if (d->m_sourceDevice != sourceDevice) {
 
+        if (d->m_sourceDevice)
+            d->unregisterDestructionHelper(d->m_sourceDevice);
+
         // Check and set parent if needed
         // to force creation in the backend
         if (sourceDevice && !sourceDevice->parent())
             sourceDevice->setParent(this);
 
         d->m_sourceDevice = sourceDevice;
+
+        // Ensures proper bookkeeping
+        if (d->m_sourceDevice)
+            d->registerDestructionHelper(sourceDevice, &QActionInput::setSourceDevice, d->m_sourceDevice);
+
         emit sourceDeviceChanged(sourceDevice);
     }
 }
diff --git a/src/input/frontend/qaxis.cpp b/src/input/frontend/qaxis.cpp
index a12b277e9..3b84e0205 100644
--- a/src/input/frontend/qaxis.cpp
+++ b/src/input/frontend/qaxis.cpp
@@ -83,6 +83,9 @@ void QAxis::addInput(QAbstractAxisInput *input)
         if (!input->parent())
             input->setParent(this);
 
+        // Ensures proper bookkeeping
+        d->registerDestructionHelper(input, &QAxis::removeInput, d->m_inputs);
+
         if (d->m_changeArbiter != nullptr) {
             const auto change = Qt3DCore::QPropertyNodeAddedChangePtr::create(id(), input);
             change->setPropertyName("input");
@@ -103,6 +106,9 @@ void QAxis::removeInput(QAbstractAxisInput *input)
         }
 
         d->m_inputs.removeOne(input);
+
+        // Remove bookkeeping connection
+        d->unregisterDestructionHelper(input);
     }
 }
 
diff --git a/src/input/frontend/qinputchord.cpp b/src/input/frontend/qinputchord.cpp
index a85efa0d2..8260e66da 100644
--- a/src/input/frontend/qinputchord.cpp
+++ b/src/input/frontend/qinputchord.cpp
@@ -152,6 +152,9 @@ void QInputChord::addChord(QAbstractActionInput *input)
     if (!d->m_chords.contains(input)) {
         d->m_chords.push_back(input);
 
+        // Ensures proper bookkeeping
+        d->registerDestructionHelper(input, &QInputChord::removeChord, d->m_chords);
+
         if (!input->parent())
             input->setParent(this);
 
@@ -180,6 +183,9 @@ void QInputChord::removeChord(QAbstractActionInput *input)
         }
 
         d->m_chords.removeOne(input);
+
+        // Remove bookkeeping connection
+        d->unregisterDestructionHelper(input);
     }
 }
 
diff --git a/src/input/frontend/qinputsequence.cpp b/src/input/frontend/qinputsequence.cpp
index 1786a9584..27f440ec7 100644
--- a/src/input/frontend/qinputsequence.cpp
+++ b/src/input/frontend/qinputsequence.cpp
@@ -205,6 +205,9 @@ void QInputSequence::addSequence(QAbstractActionInput *input)
     if (!d->m_sequences.contains(input)) {
         d->m_sequences.push_back(input);
 
+        // Ensures proper bookkeeping
+        d->registerDestructionHelper(input, &QInputSequence::removeSequence, d->m_sequences);
+
         if (!input->parent())
             input->setParent(this);
 
@@ -232,6 +235,9 @@ void QInputSequence::removeSequence(QAbstractActionInput *input)
         }
 
         d->m_sequences.removeOne(input);
+
+        // Remove bookkeeping connection
+        d->unregisterDestructionHelper(input);
     }
 }
 
diff --git a/src/input/frontend/qkeyboardhandler.cpp b/src/input/frontend/qkeyboardhandler.cpp
index a55e8ce9e..59128ad4d 100644
--- a/src/input/frontend/qkeyboardhandler.cpp
+++ b/src/input/frontend/qkeyboardhandler.cpp
@@ -196,10 +196,18 @@ void QKeyboardHandler::setSourceDevice(QKeyboardDevice *keyboardDevice)
     Q_D(QKeyboardHandler);
     if (d->m_keyboardDevice != keyboardDevice) {
 
+        if (d->m_keyboardDevice)
+            d->unregisterDestructionHelper(d->m_keyboardDevice);
+
         if (keyboardDevice && !keyboardDevice->parent())
             keyboardDevice->setParent(this);
 
         d->m_keyboardDevice = keyboardDevice;
+
+        // Ensures proper bookkeeping
+        if (d->m_keyboardDevice)
+            d->registerDestructionHelper(keyboardDevice, &QKeyboardHandler::setSourceDevice, d->m_keyboardDevice);
+
         emit sourceDeviceChanged(keyboardDevice);
     }
 }
diff --git a/src/input/frontend/qlogicaldevice.cpp b/src/input/frontend/qlogicaldevice.cpp
index f84b45001..90c2e4b05 100644
--- a/src/input/frontend/qlogicaldevice.cpp
+++ b/src/input/frontend/qlogicaldevice.cpp
@@ -171,6 +171,9 @@ void QLogicalDevice::addAction(QAction *action)
         if (!action->parent())
             action->setParent(this);
 
+        // Ensures proper bookkeeping
+        d->registerDestructionHelper(action, &QLogicalDevice::removeAction, d->m_actions);
+
         if (d->m_changeArbiter != nullptr) {
             const auto change = Qt3DCore::QPropertyNodeAddedChangePtr::create(id(), action);
             change->setPropertyName("action");
@@ -194,6 +197,9 @@ void QLogicalDevice::removeAction(QAction *action)
         }
 
         d->m_actions.removeOne(action);
+
+        // Remove bookkeeping connection
+        d->unregisterDestructionHelper(action);
     }
 }
 
@@ -225,6 +231,9 @@ void QLogicalDevice::addAxis(QAxis *axis)
         if (!axis->parent())
             axis->setParent(this);
 
+        // Ensures proper bookkeeping
+        d->registerDestructionHelper(axis, &QLogicalDevice::removeAxis, d->m_axes);
+
         if (d->m_changeArbiter != nullptr) {
             const auto change = Qt3DCore::QPropertyNodeAddedChangePtr::create(id(), axis);
             change->setPropertyName("axis");
@@ -247,6 +256,9 @@ void QLogicalDevice::removeAxis(QAxis *axis)
         }
 
         d->m_axes.removeOne(axis);
+
+        // Remove bookkeeping connection
+        d->unregisterDestructionHelper(axis);
     }
 }