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 <jpnurmi@digia.com>

src/widgets/kernel/qboxlayout.cpp

@@ -140,6 +140,7 @@ public:
     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 @@ public:
 
     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 @@ public:
     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 @@ public:
         }
         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 @@ public:
     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 @@ public:
 
     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"

tests/auto/widgets/kernel/qstackedlayout/tst_qstackedlayout.cpp

@@ -70,6 +70,7 @@ private slots:
     void removeWidget();
     void keepFocusAfterSetCurrent();
     void heigthForWidth();
+    void replaceWidget();
 
 private:
     QWidget *testWidget;
@@ -393,6 +394,27 @@ void tst_QStackedLayout::heigthForWidth()
 
 }
 
+void tst_QStackedLayout::replaceWidget()
+{
+    QWidget w;
+    QStackedLayout *stackLayout = new QStackedLayout(&w);
+
+    QLineEdit *replaceFrom = new QLineEdit;
+    QLineEdit *replaceTo = new QLineEdit;
+    stackLayout->addWidget(new QLineEdit());
+    stackLayout->addWidget(replaceFrom);
+    stackLayout->addWidget(new QLineEdit());
+    stackLayout->setCurrentWidget(replaceFrom);
+
+    QCOMPARE(stackLayout->indexOf(replaceFrom), 1);
+    QCOMPARE(stackLayout->indexOf(replaceTo), -1);
+    stackLayout->replaceWidget(replaceFrom, replaceTo);
+
+    QCOMPARE(stackLayout->indexOf(replaceFrom), -1);
+    QCOMPARE(stackLayout->indexOf(replaceTo), 1);
+    QCOMPARE(stackLayout->currentWidget(), replaceTo);
+}
+
 QTEST_MAIN(tst_QStackedLayout)
 #include "tst_qstackedlayout.moc"
 

tests/manual/widgets/kernel/kernel.pro

@@ -1,2 +1,2 @@
 TEMPLATE = subdirs
-SUBDIRS = qtooltip sizeonhide
+SUBDIRS = qtooltip sizeonhide layoutreplace

tests/manual/widgets/kernel/layoutreplace/main.cpp

@@ -0,0 +1,137 @@
+/****************************************************************************
+**
+** Copyright (C) 2013 Thorbjørn Martsum - tmartsum[at]gmail.com
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QGridLayout>
+#include <QFormLayout>
+#include <QStackedLayout>
+#include <QPushButton>
+#include <QLabel>
+#include <QApplication>
+
+class ReplaceButton : public QPushButton
+{
+    Q_OBJECT
+public:
+    ReplaceButton(const QString &text = QString("click to replace")) : QPushButton(text)
+    {
+        static int v = 0;
+        ++v;
+        QString txt = QString("click to replace %1").arg(v);
+        setText(txt);
+        connect(this, SIGNAL(clicked()), this, SLOT(replace()));
+    }
+protected slots:
+    void replace()
+    {
+        if (!parentWidget())
+            return;
+        static int n = 0;
+        ++n;
+        if (parentWidget()->layout()->replaceWidget(this, new QLabel(QString("replaced(%1)").arg(n))))
+            deleteLater();
+    }
+};
+
+class StackButtonChange : public QPushButton
+{
+    Q_OBJECT
+public:
+    StackButtonChange(QStackedLayout *l) : QPushButton("stack wdg change")
+    {
+        sl = l;
+        connect(this, SIGNAL(clicked()), this, SLOT(changeWdg()));
+    }
+protected slots:
+    void changeWdg()
+    {
+        int index = sl->indexOf(sl->currentWidget());
+        ++index;
+        if (index >= sl->count())
+            index = 0;
+        sl->setCurrentWidget(sl->itemAt(index)->widget());
+        sl->parentWidget()->update();
+    }
+protected:
+    QStackedLayout *sl;
+};
+
+int main(int argc, char **argv)                                                                                                                                                               {
+    QApplication app(argc, argv);
+    QWidget wdg1;
+    QGridLayout *l1 = new QGridLayout();
+    l1->addWidget(new ReplaceButton(), 1, 1, 2, 2, Qt::AlignCenter);
+    l1->addWidget(new ReplaceButton(), 3, 1, 1, 1, Qt::AlignRight);
+    l1->addWidget(new ReplaceButton(), 1, 3, 1, 1, Qt::AlignLeft);
+    l1->addWidget(new ReplaceButton(), 2, 3, 1, 1, Qt::AlignLeft);
+    l1->addWidget(new ReplaceButton(), 3, 2, 1, 1, Qt::AlignRight);
+    wdg1.setLayout(l1);
+    wdg1.setWindowTitle("QGridLayout");
+    wdg1.setGeometry(100, 100, 100, 100);
+    wdg1.show();
+
+    QWidget wdg2;
+    QFormLayout *l2 = new QFormLayout();
+    l2->addRow(QString("Label1"), new ReplaceButton());
+    l2->addRow(QString("Label2"), new ReplaceButton());
+    l2->addRow(new ReplaceButton(), new ReplaceButton());
+    wdg2.setLayout(l2);
+    wdg2.setWindowTitle("QFormLayout");
+    wdg2.setGeometry(100 + wdg1.sizeHint().width() + 5, 100, 100, 100);
+    wdg2.show();
+
+    QWidget wdg3;
+    QBoxLayout *l3 = new QVBoxLayout(); // new QHBoxLayout()
+    QStackedLayout *sl = new QStackedLayout();
+    sl->addWidget(new ReplaceButton());
+    sl->addWidget(new ReplaceButton());
+    sl->addWidget(new ReplaceButton());
+    l3->addLayout(sl);
+    l3->addWidget(new StackButtonChange(sl));
+    l3->addWidget(new ReplaceButton());
+    l3->addWidget(new ReplaceButton());
+    wdg3.setLayout(l3);
+    wdg3.setWindowTitle("QStackedLayout + BoxLayout");
+    wdg3.setGeometry(100, 100 + wdg1.sizeHint().height() + 30, 100 , 100);
+    wdg3.show();
+
+    app.exec();
+}
+#include "main.moc"

tests/manual/widgets/kernel/layoutreplace/main.pro

@@ -0,0 +1,2 @@
+SOURCES = main.cpp
+QT += widgets