QmlProfiler: Allow for a maximum depth in flame graph view

It gets unwieldy and eventually it produces a stack overflow if you
have insane recursion.

Change-Id: I8ae6bf018572d9b240aec01d5d3319544799e9bb
Reviewed-by: Christian Kandeler <christian.kandeler@theqtcompany.com>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

3 files changed, 39 insertions, 14 deletions

diff --git a/src/plugins/qmlprofilerextension/FlameGraphView.qml b/src/plugins/qmlprofilerextension/FlameGraphView.qml
index e834d1fad2..01e8600137 100644
--- a/src/plugins/qmlprofilerextension/FlameGraphView.qml
+++ b/src/plugins/qmlprofilerextension/FlameGraphView.qml
@@ -61,6 +61,7 @@ ScrollView {
             model: flameGraphModel
             sizeRole: FlameGraphModel.Duration
             sizeThreshold: 0.002
+            maximumDepth: 25
             y: flickable.height > height ? flickable.height - height : 0
 
             delegate: Item {
diff --git a/src/plugins/qmlprofilerextension/flamegraph.cpp b/src/plugins/qmlprofilerextension/flamegraph.cpp
index 1b7ba97826..17d7bbee91 100644
--- a/src/plugins/qmlprofilerextension/flamegraph.cpp
+++ b/src/plugins/qmlprofilerextension/flamegraph.cpp
@@ -126,7 +126,8 @@ QObject *FlameGraph::appendChild(QObject *parentObject, QQuickItem *parentItem,
 }
 
 
-int FlameGraph::buildNode(const QModelIndex &parentIndex, QObject *parentObject, int depth)
+int FlameGraph::buildNode(const QModelIndex &parentIndex, QObject *parentObject, int depth,
+                          int maximumDepth)
 {
     qreal position = 0;
     qreal skipped = 0;
@@ -135,18 +136,23 @@ int FlameGraph::buildNode(const QModelIndex &parentIndex, QObject *parentObject,
     QQmlContext *context = qmlContext(this);
     int rowCount = m_model->rowCount(parentIndex);
     int childrenDepth = depth;
-    for (int row = 0; row < rowCount; ++row) {
-        QModelIndex childIndex = m_model->index(row, 0, parentIndex);
-        qreal size = m_model->data(childIndex, m_sizeRole).toReal();
-        if (size / m_model->data(QModelIndex(), m_sizeRole).toReal() < m_sizeThreshold) {
-            skipped += size;
-            continue;
+    if (depth == maximumDepth - 1) {
+        skipped = parentSize;
+    } else {
+        for (int row = 0; row < rowCount; ++row) {
+            QModelIndex childIndex = m_model->index(row, 0, parentIndex);
+            qreal size = m_model->data(childIndex, m_sizeRole).toReal();
+            if (size / m_model->data(QModelIndex(), m_sizeRole).toReal() < m_sizeThreshold) {
+                skipped += size;
+                continue;
+            }
+
+            QObject *childObject = appendChild(parentObject, parentItem, context, childIndex,
+                                               position / parentSize, size / parentSize);
+            position += size;
+            childrenDepth = qMax(childrenDepth, buildNode(childIndex, childObject, depth + 1,
+                                                          maximumDepth));
         }
-
-        QObject *childObject = appendChild(parentObject, parentItem, context, childIndex,
-                                           position / parentSize, size / parentSize);
-        position += size;
-        childrenDepth = qMax(childrenDepth, buildNode(childIndex, childObject, depth + 1));
     }
 
     if (skipped > 0) {
@@ -169,7 +175,7 @@ void FlameGraph::rebuild()
         return;
     }
 
-    m_depth = buildNode(QModelIndex(), this, 0);
+    m_depth = buildNode(QModelIndex(), this, 0, m_maximumDepth);
     emit depthChanged(m_depth);
 }
 
diff --git a/src/plugins/qmlprofilerextension/flamegraph.h b/src/plugins/qmlprofilerextension/flamegraph.h
index 832752c3b8..d61cb1075c 100644
--- a/src/plugins/qmlprofilerextension/flamegraph.h
+++ b/src/plugins/qmlprofilerextension/flamegraph.h
@@ -109,6 +109,8 @@ class FlameGraph : public QQuickItem
     Q_PROPERTY(int sizeRole READ sizeRole WRITE setSizeRole NOTIFY sizeRoleChanged)
     Q_PROPERTY(qreal sizeThreshold READ sizeThreshold WRITE setSizeThreshold
                NOTIFY sizeThresholdChanged)
+    Q_PROPERTY(int maximumDepth READ maximumDepth WRITE setMaximumDepth
+               NOTIFY maximumDepthChanged)
     Q_PROPERTY(int depth READ depth NOTIFY depthChanged)
 
 public:
@@ -128,6 +130,19 @@ public:
 
     int depth() const;
 
+    int maximumDepth() const
+    {
+        return m_maximumDepth;
+    }
+
+    void setMaximumDepth(int maximumDepth)
+    {
+        if (maximumDepth != m_maximumDepth) {
+            m_maximumDepth = maximumDepth;
+            emit maximumDepthChanged();
+        }
+    }
+
     static FlameGraphAttached *qmlAttachedProperties(QObject *object);
 
 signals:
@@ -136,6 +151,7 @@ signals:
     void sizeRoleChanged(int role);
     void sizeThresholdChanged(qreal threshold);
     void depthChanged(int depth);
+    void maximumDepthChanged();
 
 private slots:
     void rebuild();
@@ -146,8 +162,10 @@ private:
     int m_sizeRole = 0;
     int m_depth = 0;
     qreal m_sizeThreshold = 0;
+    int m_maximumDepth = std::numeric_limits<int>::max();
 
-    int buildNode(const QModelIndex &parentIndex, QObject *parentObject, int depth);
+    int buildNode(const QModelIndex &parentIndex, QObject *parentObject, int depth,
+                  int maximumDepth);
     QObject *appendChild(QObject *parentObject, QQuickItem *parentItem, QQmlContext *context,
                          const QModelIndex &childIndex, qreal position, qreal size);
 };