Add widget replace function to QLayout

Sometimes it is nice to be able to replace a widget in a layout.

Change-Id: I23a6a65e417e94d53bc48639503db1a142bc3f10
Reviewed-by: J-P Nurmi <[email protected]>

Author: tmartsum

src/widgets/kernel/qboxlayout.cpp

@@ -140,6 +140,7 @@ class QBoxLayoutPrivate : public QLayoutPrivate
     void calcHfw(int);
 
     void effectiveMargins(int *left, int *top, int *right, int *bottom) const;
+    QLayoutItem* replaceAt(int index, QLayoutItem*) Q_DECL_OVERRIDE;
 };
 
 QBoxLayoutPrivate::~QBoxLayoutPrivate()
@@ -444,6 +445,21 @@ void QBoxLayoutPrivate::calcHfw(int w)
     hfwMinHeight = mh;
 }
 
+QLayoutItem* QBoxLayoutPrivate::replaceAt(int index, QLayoutItem *item)
+{
+    Q_Q(QBoxLayout);
+    if (!item)
+        return 0;
+    QBoxLayoutItem *b = list.value(index);
+    if (!b)
+        return 0;
+    QLayoutItem *r = b->item;
+
+    b->item = item;
+    q->invalidate();
+    return r;
+}
+
 
 /*!
     \class QBoxLayout

src/widgets/kernel/qformlayout.cpp

@@ -246,6 +246,7 @@ class QFormLayoutPrivate : public QLayoutPrivate
 
     int hSpacing;
     int vSpacing;
+    QLayoutItem* replaceAt(int index, QLayoutItem*) Q_DECL_OVERRIDE;
 };
 
 QFormLayoutPrivate::QFormLayoutPrivate()
@@ -1001,6 +1002,32 @@ QStyle* QFormLayoutPrivate::getStyle() const
         return QApplication::style();
 }
 
+QLayoutItem* QFormLayoutPrivate::replaceAt(int index, QLayoutItem *newitem)
+{
+    Q_Q(QFormLayout);
+    if (!newitem)
+        return 0;
+    const int storageIndex = storageIndexFromLayoutItem(m_matrix, m_things.value(index));
+    if (storageIndex == -1) {
+        // ### Qt6 - fix warning too when this class becomes public
+        qWarning("QFormLayoutPrivate::replaceAt: Invalid index %d", index);
+        return 0;
+    }
+
+    int row, col;
+    QFormLayoutPrivate::ItemMatrix::storageIndexToPosition(storageIndex, &row, &col);
+    Q_ASSERT(m_matrix(row, col));
+
+    QFormLayoutItem *item = m_matrix(row, col);
+    Q_ASSERT(item);
+
+    QLayoutItem *olditem = item->item;
+    item->item = newitem;
+
+    q->invalidate();
+    return olditem;
+}
+
 /*!
     \class QFormLayout
     \since 4.4

src/widgets/kernel/qgridlayout.cpp

@@ -85,6 +85,7 @@ class QGridBox
     void setGeometry(const QRect &r) { item_->setGeometry(r); }
     Qt::Alignment alignment() const { return item_->alignment(); }
     QLayoutItem *item() { return item_; }
+    void setItem(QLayoutItem *newitem) { item_ = newitem; }
     QLayoutItem *takeItem() { QLayoutItem *i = item_; item_ = 0; return i; }
 
     int hStretch() { return item_->widget() ?
@@ -171,6 +172,18 @@ class QGridLayoutPrivate : public QLayoutPrivate
         }
         return 0;
     }
+    QLayoutItem* replaceAt(int index, QLayoutItem *newitem) Q_DECL_OVERRIDE
+    {
+        if (!newitem)
+            return 0;
+        QLayoutItem *item = 0;
+        QGridBox *b = things.value(index);
+        if (b) {
+            item = b->takeItem();
+            b->setItem(newitem);
+        }
+        return item;
+    }
 
     void getItemPosition(int index, int *row, int *column, int *rowSpan, int *columnSpan) const {
         if (index < things.count()) {

src/widgets/kernel/qlayout.cpp

@@ -1108,6 +1108,54 @@ bool QLayout::activate()
     return true;
 }
 
+/*!
+    \since 5.2
+
+    Searches for widget \a from and replaces it with widget \a to if found.
+    Returns the layout item that contains the widget \a from on success. Otherwise \c 0 is returned.
+    If \a recursive is \c true, sub-layouts are searched for doing the replacement. Notice that the returned item therefore might not belong to this layout, but to a sub-layout.
+
+    The returned layout item is no longer owned by the layout and should be either deleted or inserted to another layout. The widget \a from is no longer managed by the layout and may need to be deleted or hidden. The parent of widget \a from is left unchanged.
+
+    This function works for the built-in Qt layouts, but might not work for custom layouts.
+
+    \sa indexOf()
+*/
+
+//### Qt 6 make this function virtual
+QLayoutItem* QLayout::replaceWidget(QWidget *from, QWidget *to, bool recursive)
+{
+    Q_D(QLayout);
+    if (!from || !to)
+        return 0;
+
+    int index = -1;
+    QLayoutItem *item = 0;
+    for (int u = 0; u < count(); ++u) {
+        item = itemAt(u);
+        if (item->widget() == from) {
+            index = u;
+            break;
+        }
+        if (item && item->layout() && recursive) {
+            QLayoutItem *r = item->layout()->replaceWidget(from, to, true);
+            if (r)
+                return r;
+        }
+    }
+    if (index == -1)
+        return 0;
+
+    QLayoutItem *newitem = new QWidgetItem(to);
+    newitem->setAlignment(item->alignment());
+    QLayoutItem *r = d->replaceAt(index, newitem);
+    if (!r)
+        delete newitem;
+    else
+        addChildWidget(to);
+    return r;
+}
+
 /*!
     \fn QLayoutItem *QLayout::itemAt(int index) const
 

src/widgets/kernel/qlayout.h

@@ -130,6 +130,7 @@ class Q_WIDGETS_EXPORT QLayout : public QObject, public QLayoutItem
     virtual int count() const = 0;
     bool isEmpty() const;
     QSizePolicy::ControlTypes controlTypes() const;
+    QLayoutItem* replaceWidget(QWidget *from, QWidget *to, bool recursive = true);
 
     int totalHeightForWidth(int w) const;
     QSize totalMinimumSize() const;

src/widgets/kernel/qlayout_p.h

@@ -61,6 +61,7 @@ QT_BEGIN_NAMESPACE
 
 class QWidgetItem;
 class QSpacerItem;
+class QLayoutItem;
 
 class Q_WIDGETS_EXPORT QLayoutPrivate : public QObjectPrivate
 {
@@ -78,6 +79,7 @@ class Q_WIDGETS_EXPORT QLayoutPrivate : public QObjectPrivate
 
     static QWidgetItem *createWidgetItem(const QLayout *layout, QWidget *widget);
     static QSpacerItem *createSpacerItem(const QLayout *layout, int w, int h, QSizePolicy::Policy hPolicy = QSizePolicy::Minimum, QSizePolicy::Policy vPolicy = QSizePolicy::Minimum);
+    virtual QLayoutItem* replaceAt(int index, QLayoutItem *newitem) { Q_UNUSED(index); Q_UNUSED(newitem); return 0; }
 
     static QWidgetItemFactoryMethod widgetItemFactoryMethod;
     static QSpacerItemFactoryMethod spacerItemFactoryMethod;

src/widgets/kernel/qstackedlayout.cpp

@@ -53,11 +53,29 @@ class QStackedLayoutPrivate : public QLayoutPrivate
     Q_DECLARE_PUBLIC(QStackedLayout)
 public:
     QStackedLayoutPrivate() : index(-1), stackingMode(QStackedLayout::StackOne) {}
+    QLayoutItem* replaceAt(int index, QLayoutItem *newitem) Q_DECL_OVERRIDE;
     QList<QLayoutItem *> list;
     int index;
     QStackedLayout::StackingMode stackingMode;
 };
 
+QLayoutItem* QStackedLayoutPrivate::replaceAt(int idx, QLayoutItem *newitem)
+{
+    Q_Q(QStackedLayout);
+    if (idx < 0 || idx >= list.size() || !newitem)
+        return 0;
+    QWidget *wdg = newitem->widget();
+    if (!wdg) {
+        qWarning("QStackedLayout::replaceAt: Only widgets can be added");
+        return 0;
+    }
+    QLayoutItem *orgitem = list.at(idx);
+    list.replace(idx, newitem);
+    if (idx == index)
+        q->setCurrentIndex(index);
+    return orgitem;
+}
+
 /*!
     \class QStackedLayout
 

tests/auto/widgets/kernel/qboxlayout/tst_qboxlayout.cpp

@@ -79,6 +79,7 @@ private slots:
 
     void taskQTBUG_7103_minMaxWidthNotRespected();
     void taskQTBUG_27420_takeAtShouldUnparentLayout();
+    void replaceWidget();
 };
 
 class CustomLayoutStyle : public QProxyStyle
@@ -328,7 +329,6 @@ void tst_QBoxLayout::taskQTBUG_27420_takeAtShouldUnparentLayout()
         QVERIFY(!inner.isNull());
 }
 
-
 struct Descr
 {
     Descr(int min, int sh, int max = -1, bool exp= false, int _stretch = 0, bool _empty = false)
@@ -507,5 +507,24 @@ void tst_QBoxLayout::testLayoutEngine()
     }
 }
 
+void tst_QBoxLayout::replaceWidget()
+{
+    QWidget w;
+    QBoxLayout *boxLayout = new QVBoxLayout(&w);
+
+    QLineEdit *replaceFrom = new QLineEdit;
+    QLineEdit *replaceTo = new QLineEdit;
+    boxLayout->addWidget(new QLineEdit());
+    boxLayout->addWidget(replaceFrom);
+    boxLayout->addWidget(new QLineEdit());
+
+    QCOMPARE(boxLayout->indexOf(replaceFrom), 1);
+    QCOMPARE(boxLayout->indexOf(replaceTo), -1);
+    boxLayout->replaceWidget(replaceFrom, replaceTo);
+
+    QCOMPARE(boxLayout->indexOf(replaceFrom), -1);
+    QCOMPARE(boxLayout->indexOf(replaceTo), 1);
+}
+
 QTEST_MAIN(tst_QBoxLayout)
 #include "tst_qboxlayout.moc"

tests/auto/widgets/kernel/qformlayout/tst_qformlayout.cpp

@@ -122,6 +122,7 @@ private slots:
     void itemAt();
     void takeAt();
     void layoutAlone();
+    void replaceWidget();
 /*
     void setGeometry(const QRect &rect);
     QSize minimumSize() const;
@@ -934,6 +935,54 @@ void tst_QFormLayout::taskQTBUG_27420_takeAtShouldUnparentLayout()
         QVERIFY(!inner.isNull());
 }
 
+void tst_QFormLayout::replaceWidget()
+{
+    QWidget w;
+    QFormLayout *layout = new QFormLayout();
+    w.setLayout(layout);
+    QLineEdit *edit1 = new QLineEdit();
+    QLineEdit *edit2 = new QLineEdit();
+    QLineEdit *edit3 = new QLineEdit();
+    QLabel *label1 = new QLabel();
+    QLabel *label2 = new QLabel();
+
+    layout->addRow("Label", edit1);
+    layout->addRow(label1, edit2);
+
+    // Verify controls not in layout
+    QCOMPARE(layout->indexOf(edit3), -1);
+    QCOMPARE(layout->indexOf(label2), -1);
+
+    // Verify controls in layout
+    int editIndex = layout->indexOf(edit1);
+    int labelIndex = layout->indexOf(label1);
+    QVERIFY(editIndex > 0);
+    QVERIFY(labelIndex > 0);
+    int rownum;
+    QFormLayout::ItemRole role;
+
+    // replace editor
+    layout->replaceWidget(edit1, edit3);
+    edit1->hide(); // Not strictly needed for the test, but for normal usage it is.
+    QCOMPARE(layout->indexOf(edit1), -1);
+    QCOMPARE(layout->indexOf(edit3), editIndex);
+    QCOMPARE(layout->indexOf(label1), labelIndex);
+    rownum = -1;
+    role = QFormLayout::SpanningRole;
+    layout->getWidgetPosition(edit3, &rownum, &role);
+    QCOMPARE(rownum, 0);
+    QCOMPARE(role, QFormLayout::FieldRole);
+
+    layout->replaceWidget(label1, label2);
+    label1->hide();
+    QCOMPARE(layout->indexOf(label1), -1);
+    QCOMPARE(layout->indexOf(label2), labelIndex);
+    layout->getWidgetPosition(label2, &rownum, &role);
+    QCOMPARE(rownum, 1);
+    QCOMPARE(role, QFormLayout::LabelRole);
+
+}
+
 QTEST_MAIN(tst_QFormLayout)
 
 #include "tst_qformlayout.moc"

tests/auto/widgets/kernel/qgridlayout/tst_qgridlayout.cpp

@@ -101,6 +101,7 @@ private slots:
     void distributeMultiCell();
 
     void taskQTBUG_27420_takeAtShouldUnparentLayout();
+    void replaceWidget();
 
 private:
     QWidget *testWidget;
@@ -1656,5 +1657,49 @@ void tst_QGridLayout::taskQTBUG_27420_takeAtShouldUnparentLayout()
         QVERIFY(!inner.isNull());
 }
 
+void tst_QGridLayout::replaceWidget()
+{
+    QWidget wdg;
+    QGridLayout *l = new QGridLayout();
+    const int itemCount = 9;
+    QLabel *labels[itemCount];
+
+    // setup layout
+    for (int n = 0; n < itemCount; ++n) {
+        int x = n % 3;
+        int y = n / 3;
+        labels[n] = new QLabel(QString("label %1").arg(n));
+        Qt::Alignment align = (n % 3 ? Qt::AlignLeft : Qt::AlignRight);
+        l->addWidget(labels[n], x * 3, y * 3, (n % 2) + 1, (n + 1) % 2 + 1, align);
+    }
+    wdg.setLayout(l);
+
+    // iterate and replace
+    for (int n = 0; n < itemCount; n += 2) {
+        int i = l->indexOf(labels[n]);
+        int fromRow, fromCol, fromRowSpan, fromColSpan;
+        l->getItemPosition(i, &fromRow, &fromCol, &fromRowSpan, &fromColSpan);
+        Qt::Alignment fromAlign = l->itemAt(i)->alignment();
+        // do replace
+        QPushButton *pb = new QPushButton("replaced");
+        QLayoutItem *olditem = l->replaceWidget(labels[n], pb);
+        // verify
+        QCOMPARE(i, l->indexOf(pb));
+        QVERIFY(olditem != 0);
+        QCOMPARE(l->indexOf(labels[n]), -1);
+        int toRow, toCol, toRowSpan, toColSpan;
+        l->getItemPosition(i, &toRow, &toCol, &toRowSpan, &toColSpan);
+        QCOMPARE(fromRow, toRow);
+        QCOMPARE(fromCol, toCol);
+        QCOMPARE(fromRowSpan, toRowSpan);
+        QCOMPARE(fromColSpan, toColSpan);
+        Qt::Alignment toAlign = l->itemAt(i)->alignment();
+        QCOMPARE(fromAlign, toAlign);
+        // clean up
+        olditem->widget()->deleteLater();
+        delete olditem;
+    }
+}
+
 QTEST_MAIN(tst_QGridLayout)
 #include "tst_qgridlayout.moc"