QFormLayout: take the correct row in takeRow()

I didn't even try to understand what the old code was trying to do;
once you're told by a user that the code is wrong, you see that it is.

Fixed by just using the row as passed to takeRow() instead of trying
to do some storage-index calculations. The m_matrix indexing operator
does it all for us.

Added a test that checks that the expected field widget gets
returned. Fixed expected test data that was wrong, and just checking
that the implementation behaves as implemented, instead of as
documented.

Amends change 8fbae648db3bc51bafacfe1f88e40561d357e60a.

[ChangeLog][QtWidget][QFormLayout] The functions takeRow() and
removeRow(), new in 5.8.0, now take and remove the correct row.

Task-number: QTBUG-58693
Task-number: QTBUG-15990
Change-Id: I7185ccbc6c03e2579741cad5c0c821d3ed165474
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

2 files changed, 13 insertions, 15 deletions

diff --git a/src/widgets/kernel/qformlayout.cpp b/src/widgets/kernel/qformlayout.cpp
index f3f7280030..6b134379c6 100644
--- a/src/widgets/kernel/qformlayout.cpp
+++ b/src/widgets/kernel/qformlayout.cpp
@@ -1551,24 +1551,19 @@ QFormLayout::TakeRowResult QFormLayout::takeRow(int row)
 {
     Q_D(QFormLayout);
 
-    const int storageIndex = storageIndexFromLayoutItem(d->m_matrix, d->m_things.value(row));
-    if (Q_UNLIKELY(storageIndex == -1)) {
+    if (Q_UNLIKELY(!(uint(row) < uint(d->m_matrix.rowCount())))) {
         qWarning("QFormLayout::takeRow: Invalid row %d", row);
         return TakeRowResult();
     }
 
-    int storageRow, dummy;
-    QFormLayoutPrivate::ItemMatrix::storageIndexToPosition(storageIndex, &storageRow, &dummy);
-    Q_ASSERT(d->m_matrix(storageRow, dummy));
-
-    QFormLayoutItem *label = d->m_matrix(storageRow, 0);
-    QFormLayoutItem *field = d->m_matrix(storageRow, 1);
+    QFormLayoutItem *label = d->m_matrix(row, 0);
+    QFormLayoutItem *field = d->m_matrix(row, 1);
 
     Q_ASSERT(field);
 
     d->m_things.removeOne(label);
     d->m_things.removeOne(field);
-    d->m_matrix.removeRow(storageRow);
+    d->m_matrix.removeRow(row);
 
     invalidate();
 
diff --git a/tests/auto/widgets/kernel/qformlayout/tst_qformlayout.cpp b/tests/auto/widgets/kernel/qformlayout/tst_qformlayout.cpp
index d8239b5a28..c324a4bd56 100644
--- a/tests/auto/widgets/kernel/qformlayout/tst_qformlayout.cpp
+++ b/tests/auto/widgets/kernel/qformlayout/tst_qformlayout.cpp
@@ -757,13 +757,14 @@ void tst_QFormLayout::removeRow()
 
     layout->removeRow(1);
 
-    QVERIFY(!w1);
-    QCOMPARE(layout->count(), 1);
+    QVERIFY(w1);
+    QVERIFY(!w2);
+    QCOMPARE(layout->count(), 2);
     QCOMPARE(layout->rowCount(), 1);
 
     layout->removeRow(0);
 
-    QVERIFY(!w2);
+    QVERIFY(!w1);
     QCOMPARE(layout->count(), 0);
     QCOMPARE(layout->rowCount(), 0);
 }
@@ -863,17 +864,19 @@ void tst_QFormLayout::takeRow()
 
     QVERIFY(w2);
     QVERIFY(result.fieldItem);
-    QVERIFY(result.labelItem);
-    QCOMPARE(layout->count(), 1);
+    QVERIFY(!result.labelItem);
+    QCOMPARE(layout->count(), 2);
     QCOMPARE(layout->rowCount(), 1);
+    QCOMPARE(result.fieldItem->widget(), w2.data());
 
     result = layout->takeRow(0);
 
     QVERIFY(w1);
     QVERIFY(result.fieldItem);
-    QVERIFY(!result.labelItem);
+    QVERIFY(result.labelItem);
     QCOMPARE(layout->count(), 0);
     QCOMPARE(layout->rowCount(), 0);
+    QCOMPARE(result.fieldItem->widget(), w1.data());
 
     result = layout->takeRow(0);