QTreeView: add expandRecursively() to expand all items below an index

QTreeView only had functions to either expand all items or until a given
depth. What was missing is to expand all subitems for an index
programmatically which is added with this patch.

[ChangeLog][QtWidgets][QTreeView] Added expandRecursively() to expand
all items below a given index

Fixes: QTBUG-10482
Change-Id: I8fc4d50b0b7e90245840c99a0188f13c0670253a
Reviewed-by: Samuel Gaist <samuel.gaist@idiap.ch>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

3 files changed, 126 insertions, 49 deletions

diff --git a/src/widgets/itemviews/qtreeview.cpp b/src/widgets/itemviews/qtreeview.cpp
index 60da0eb6c3..743832b214 100644
--- a/src/widgets/itemviews/qtreeview.cpp
+++ b/src/widgets/itemviews/qtreeview.cpp
@@ -1985,21 +1985,7 @@ void QTreeView::keyPressEvent(QKeyEvent *event)
     if (d->isIndexValid(current) && d->model && d->itemsExpandable) {
         switch (event->key()) {
         case Qt::Key_Asterisk: {
-            // do layouting only once after expanding is done
-            d->doDelayedItemsLayout();
-            QStack<QModelIndex> parents;
-            parents.push(current);
-            while (!parents.isEmpty()) {
-                QModelIndex parent = parents.pop();
-                for (int row = 0; row < d->model->rowCount(parent); ++row) {
-                    QModelIndex child = d->model->index(row, 0, parent);
-                    if (!d->isIndexValid(child))
-                        break;
-                    parents.push(child);
-                    expand(child);
-                }
-            }
-            expand(current);
+            expandRecursively(current);
             break; }
         case Qt::Key_Plus:
             expand(current);
@@ -2694,7 +2680,7 @@ QSize QTreeView::viewportSizeHint() const
   \since 4.2
   Expands all expandable items.
 
-  Warning: if the model contains a large number of items,
+  \warning: if the model contains a large number of items,
   this function will take some time to execute.
 
   \sa collapseAll(), expand(), collapse(), setExpanded()
@@ -2710,6 +2696,50 @@ void QTreeView::expandAll()
 }
 
 /*!
+  \since 5.13
+  Expands the item at the given \a index and all its children to the
+  given \a depth. The \a depth is relative to the given \a index.
+  A \a depth of -1 will expand all children, a \a depth of 0 will
+  only expand the given \a index.
+
+  \warning: if the model contains a large number of items,
+  this function will take some time to execute.
+
+  \sa expandAll()
+*/
+void QTreeView::expandRecursively(const QModelIndex &index, int depth)
+{
+    Q_D(QTreeView);
+
+    if (depth < -1)
+        return;
+    // do layouting only once after expanding is done
+    d->doDelayedItemsLayout();
+    expand(index);
+    if (depth == 0)
+        return;
+    QStack<QPair<QModelIndex, int>> parents;
+    parents.push({index, 0});
+    while (!parents.isEmpty()) {
+        const QPair<QModelIndex, int> elem = parents.pop();
+        const QModelIndex &parent = elem.first;
+        const int curDepth = elem.second;
+        const int rowCount = d->model->rowCount(parent);
+        for (int row = 0; row < rowCount; ++row) {
+            const QModelIndex child = d->model->index(row, 0, parent);
+            if (!d->isIndexValid(child))
+                break;
+            if (depth == -1 || curDepth + 1 < depth)
+                parents.push({child, curDepth + 1});
+            if (d->isIndexExpanded(child))
+                continue;
+            if (d->storeExpanded(child))
+                emit expanded(child);
+        }
+    }
+}
+
+/*!
   \since 4.2
 
   Collapses all expanded items.
diff --git a/src/widgets/itemviews/qtreeview.h b/src/widgets/itemviews/qtreeview.h
index 33dbf1c1ce..ee65cf4265 100644
--- a/src/widgets/itemviews/qtreeview.h
+++ b/src/widgets/itemviews/qtreeview.h
@@ -160,6 +160,7 @@ public Q_SLOTS:
     void resizeColumnToContents(int column);
     void sortByColumn(int column);
     void expandAll();
+    void expandRecursively(const QModelIndex &index, int depth = -1);
     void collapseAll();
     void expandToDepth(int depth);
 
diff --git a/tests/auto/widgets/itemviews/qtreeview/tst_qtreeview.cpp b/tests/auto/widgets/itemviews/qtreeview/tst_qtreeview.cpp
index f4a73b8b4a..b8c36f9b21 100644
--- a/tests/auto/widgets/itemviews/qtreeview/tst_qtreeview.cpp
+++ b/tests/auto/widgets/itemviews/qtreeview/tst_qtreeview.cpp
@@ -1647,50 +1647,96 @@ void tst_QTreeView::expandAndCollapse()
     }
 }
 
+static void checkExpandState(const QAbstractItemModel &model, const QTreeView &view,
+                             const QModelIndex &startIdx, bool bIsExpanded, int *count)
+{
+    *count = 0;
+    QStack<QModelIndex> parents;
+    parents.push(startIdx);
+    if (startIdx.isValid()) {
+        QCOMPARE(view.isExpanded(startIdx), bIsExpanded);
+        *count += 1;
+    }
+    while (!parents.isEmpty()) {
+        const QModelIndex p = parents.pop();
+        const int rows = model.rowCount(p);
+        for (int r = 0; r < rows; ++r) {
+            const QModelIndex c = model.index(r, 0, p);
+            QCOMPARE(view.isExpanded(c), bIsExpanded);
+            parents.push(c);
+        }
+        *count += rows;
+    }
+}
+
 void tst_QTreeView::expandAndCollapseAll()
 {
-    QtTestModel model(3, 2);
-    model.levels = 2;
+    QStandardItemModel model;
+    // QtTestModel has a broken parent/child handling which will break the test
+    for (int i1 = 0; i1 < 3; ++i1) {
+        QStandardItem *s1 = new QStandardItem;
+        s1->setText(QString::number(i1));
+        model.appendRow(s1);
+        for (int i2 = 0; i2 < 3; ++i2) {
+            QStandardItem *s2 = new QStandardItem;
+            s2->setText(QStringLiteral("%1 - %2").arg(i1).arg(i2));
+            s1->appendRow(s2);
+            for (int i3 = 0; i3 < 3; ++i3) {
+                QStandardItem *s3 = new QStandardItem;
+                s3->setText(QStringLiteral("%1 - %2 - %3").arg(i1).arg(i2).arg(i3));
+                s2->appendRow(s3);
+            }
+        }
+    }
     QTreeView view;
     view.setUniformRowHeights(true);
     view.setModel(&model);
+    view.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&view));
 
-    QSignalSpy expandedSpy(&view, SIGNAL(expanded(QModelIndex)));
-    QSignalSpy collapsedSpy(&view, SIGNAL(collapsed(QModelIndex)));
+    QSignalSpy expandedSpy(&view, &QTreeView::expanded);
+    QSignalSpy collapsedSpy(&view, &QTreeView::collapsed);
+    int count;
 
     view.expandAll();
-    view.show();
-
+    checkExpandState(model, view, QModelIndex(), true, &count);
     QCOMPARE(collapsedSpy.count(), 0);
+    QCOMPARE(expandedSpy.count(),  39); // == 3 (first) + 9 (second) + 27 (third level)
+    QCOMPARE(count, 39);
 
-    QStack<QModelIndex> parents;
-    parents.push(QModelIndex());
-    int count = 0;
-    while (!parents.isEmpty()) {
-        QModelIndex p = parents.pop();
-        int rows = model.rowCount(p);
-        for (int r = 0; r < rows; ++r)
-            QVERIFY(view.isExpanded(model.index(r, 0, p)));
-        count += rows;
-        for (int r = 0; r < rows; ++r)
-            parents.push(model.index(r, 0, p));
-    }
-    QCOMPARE(expandedSpy.count(), 12); // == (3+1)*(2+1) from QtTestModel model(3, 2);
-
+    collapsedSpy.clear();
+    expandedSpy.clear();
     view.collapseAll();
-
-    parents.push(QModelIndex());
-    count = 0;
-    while (!parents.isEmpty()) {
-        QModelIndex p = parents.pop();
-        int rows = model.rowCount(p);
-        for (int r = 0; r < rows; ++r)
-            QVERIFY(!view.isExpanded(model.index(r, 0, p)));
-        count += rows;
-        for (int r = 0; r < rows; ++r)
-            parents.push(model.index(r, 0, p));
-    }
-    QCOMPARE(collapsedSpy.count(), 12);
+    checkExpandState(model, view, QModelIndex(), false, &count);
+    QCOMPARE(collapsedSpy.count(), 39);
+    QCOMPARE(expandedSpy.count(), 0);
+    QCOMPARE(count, 39);
+
+    collapsedSpy.clear();
+    expandedSpy.clear();
+    view.expandRecursively(model.index(0, 0));
+    QCOMPARE(expandedSpy.count(), 13); // 1 + 3 + 9
+
+    checkExpandState(model, view, model.index(0, 0), true, &count);
+    QCOMPARE(count, 13);
+    checkExpandState(model, view, model.index(1, 0), false, &count);
+    QCOMPARE(count, 13);
+    checkExpandState(model, view, model.index(2, 0), false, &count);
+    QCOMPARE(count, 13);
+
+    expandedSpy.clear();
+    view.collapseAll();
+    view.expandRecursively(model.index(0, 0), 1);
+    QCOMPARE(expandedSpy.count(), 4); // 1 + 3
+    view.expandRecursively(model.index(0, 0), 2);
+    QCOMPARE(expandedSpy.count(), 13); // (1 + 3) + 9
+
+    checkExpandState(model, view, model.index(0, 0), true, &count);
+    QCOMPARE(count, 13);
+    checkExpandState(model, view, model.index(1, 0), false, &count);
+    QCOMPARE(count, 13);
+    checkExpandState(model, view, model.index(2, 0), false, &count);
+    QCOMPARE(count, 13);
 }
 
 void tst_QTreeView::expandWithNoChildren()