QSizePolicy - add retainSizeWhenHidden

Sometimes it is nice that hiding a widget does not affect the
layout. This patch makes that possible by allowing hidden
widgets to take up space.

Change-Id: Ifbc1cdee0e112950acc025919b98199ea9558db7
Reviewed-by: Jan Arve Sæther <jan-arve.saether@digia.com>
Reviewed-by: Thorbjørn Lund Martsum <tmartsum@gmail.com>

11 files changed, 217 insertions, 7 deletions

diff --git a/dist/changes-5.2.0 b/dist/changes-5.2.0
index a6beaa441d..dab73b7a2e 100644
--- a/dist/changes-5.2.0
+++ b/dist/changes-5.2.0
@@ -32,6 +32,8 @@ QtWidgets
 
 - QFileDialog::setDefaultSuffix() removes leading dot characters.
 
+- QSizePolicy got a retainSizeWhenHidden attribute.
+
 QtCore
 ------
 - [QTBUG-30250] QTime, QDateTime:
diff --git a/src/widgets/kernel/qlayout.cpp b/src/widgets/kernel/qlayout.cpp
index a65c34adf5..8541dd984d 100644
--- a/src/widgets/kernel/qlayout.cpp
+++ b/src/widgets/kernel/qlayout.cpp
@@ -1443,7 +1443,7 @@ QDataStream &operator<<(QDataStream &stream, const QSizePolicy &policy)
                     policy.bits.hfw << 8 |          // [8]
                     policy.bits.ctype << 9 |        // [9, 13]
                     policy.bits.wfh << 14 |         // [14]
-                  //policy.bits.padding << 15 |     // [15]
+                    policy.bits.retainSizeWhenHidden << 15 |     // [15]
                     policy.bits.verStretch << 16 |  // [16, 23]
                     policy.bits.horStretch << 24);  // [24, 31]
     return stream << data;
@@ -1468,7 +1468,7 @@ QDataStream &operator>>(QDataStream &stream, QSizePolicy &policy)
     policy.bits.hfw =        VALUE_OF_BITS(data, 8, 1);
     policy.bits.ctype =      VALUE_OF_BITS(data, 9, 5);
     policy.bits.wfh =        VALUE_OF_BITS(data, 14, 1);
-    policy.bits.padding =   0;
+    policy.bits.retainSizeWhenHidden =    VALUE_OF_BITS(data, 15, 1);
     policy.bits.verStretch = VALUE_OF_BITS(data, 16, 8);
     policy.bits.horStretch = VALUE_OF_BITS(data, 24, 8);
     return stream;
diff --git a/src/widgets/kernel/qlayoutitem.cpp b/src/widgets/kernel/qlayoutitem.cpp
index 223bcf1d9b..a99ea77ce2 100644
--- a/src/widgets/kernel/qlayoutitem.cpp
+++ b/src/widgets/kernel/qlayoutitem.cpp
@@ -682,7 +682,7 @@ bool QSpacerItem::isEmpty() const
 */
 bool QWidgetItem::isEmpty() const
 {
-    return wid->isHidden() || wid->isWindow();
+    return (wid->isHidden() && !wid->sizePolicy().retainSizeWhenHidden()) || wid->isWindow();
 }
 
 /*!
diff --git a/src/widgets/kernel/qsizepolicy.h b/src/widgets/kernel/qsizepolicy.h
index 2fe85cbe0c..9c6d67410a 100644
--- a/src/widgets/kernel/qsizepolicy.h
+++ b/src/widgets/kernel/qsizepolicy.h
@@ -131,6 +131,9 @@ public:
     void setHorizontalStretch(int stretchFactor) { bits.horStretch = static_cast<quint32>(qBound(0, stretchFactor, 255)); }
     void setVerticalStretch(int stretchFactor) { bits.verStretch = static_cast<quint32>(qBound(0, stretchFactor, 255)); }
 
+    bool retainSizeWhenHidden() const { return bits.retainSizeWhenHidden; }
+    void setRetainSizeWhenHidden(bool retainSize) { bits.retainSizeWhenHidden = retainSize; }
+
     void transpose();
 
 
@@ -150,7 +153,7 @@ private:
             quint32 ctype : 5;
             quint32 hfw : 1;
             quint32 wfh : 1;
-            quint32 padding : 1;   // feel free to use
+            quint32 retainSizeWhenHidden : 1;
         } bits;
         quint32 data;
     };
diff --git a/src/widgets/kernel/qsizepolicy.qdoc b/src/widgets/kernel/qsizepolicy.qdoc
index 6af694d999..2c088113e1 100644
--- a/src/widgets/kernel/qsizepolicy.qdoc
+++ b/src/widgets/kernel/qsizepolicy.qdoc
@@ -341,6 +341,23 @@
 */
 
 /*!
+    \fn void QSizePolicy::retainSizeWhenHidden() const
+
+    Returns if the layout should retain the widgets size when it is hidden. This is by default false.
+
+    \sa setRetainSizeWhenHidden()
+*/
+
+/*!
+   \fn void QSizePolicy::setRetainSizeWhenHidden(bool retainSize)
+
+    Set if a layout should retain the widgets size when it is hidden.
+    If \a retainSize is true the layout will not be changed by hiding the widget.
+
+    \sa retainSizeWhenHidden()
+*/
+
+/*!
     \enum QSizePolicy::ControlType
     \since 4.3
 
diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index a0c723fa0d..2d19175725 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -264,6 +264,7 @@ QWidgetPrivate::QWidgetPrivate(int version)
       , bg_role(QPalette::NoRole)
       , dirtyOpaqueChildren(1)
       , isOpaque(0)
+      , retainSizeWhenHiddenChanged(0)
       , inDirtyList(0)
       , isScrolled(0)
       , isMoved(0)
@@ -9254,6 +9255,10 @@ void QWidget::setSizePolicy(QSizePolicy policy)
     setAttribute(Qt::WA_WState_OwnSizePolicy);
     if (policy == d->size_policy)
         return;
+
+    if (d->size_policy.retainSizeWhenHidden() != policy.retainSizeWhenHidden())
+        d->retainSizeWhenHiddenChanged = 1;
+
     d->size_policy = policy;
 
 #ifndef QT_NO_GRAPHICSVIEW
@@ -9264,6 +9269,7 @@ void QWidget::setSizePolicy(QSizePolicy policy)
 #endif
 
     updateGeometry();
+    d->retainSizeWhenHiddenChanged = 0;
 
     if (isWindow() && d->maybeTopData())
         d->topData()->sizeAdjusted = false;
@@ -9392,7 +9398,9 @@ void QWidgetPrivate::updateGeometry_helper(bool forceUpdate)
         widgetItem->invalidateSizeCache();
     QWidget *parent;
     if (forceUpdate || !extra || extra->minw != extra->maxw || extra->minh != extra->maxh) {
-        if (!q->isWindow() && !q->isHidden() && (parent = q->parentWidget())) {
+        const int isHidden = q->isHidden() && !size_policy.retainSizeWhenHidden() && !retainSizeWhenHiddenChanged;
+
+        if (!q->isWindow() && !isHidden && (parent = q->parentWidget())) {
             if (parent->d_func()->layout)
                 parent->d_func()->layout->invalidate();
             else if (parent->isVisible())
diff --git a/src/widgets/kernel/qwidget_p.h b/src/widgets/kernel/qwidget_p.h
index 111dd7f9c5..0580f72e11 100644
--- a/src/widgets/kernel/qwidget_p.h
+++ b/src/widgets/kernel/qwidget_p.h
@@ -688,6 +688,7 @@ public:
     QPalette::ColorRole bg_role : 8;
     uint dirtyOpaqueChildren : 1;
     uint isOpaque : 1;
+    uint retainSizeWhenHiddenChanged : 1;
     uint inDirtyList : 1;
     uint isScrolled : 1;
     uint isMoved : 1;
diff --git a/tests/auto/widgets/kernel/qlayout/tst_qlayout.cpp b/tests/auto/widgets/kernel/qlayout/tst_qlayout.cpp
index 2b9b4fd761..ab2df2e250 100644
--- a/tests/auto/widgets/kernel/qlayout/tst_qlayout.cpp
+++ b/tests/auto/widgets/kernel/qlayout/tst_qlayout.cpp
@@ -84,6 +84,7 @@ private slots:
     void controlTypes();
     void controlTypes2();
     void adjustSizeShouldMakeSureLayoutIsActivated();
+    void testRetainSizeWhenHidden();
 };
 
 tst_QLayout::tst_QLayout()
@@ -350,5 +351,47 @@ void tst_QLayout::adjustSizeShouldMakeSureLayoutIsActivated()
     QCOMPARE(main.size(), QSize(200, 10));
 }
 
+void tst_QLayout::testRetainSizeWhenHidden()
+{
+    QWidget widget;
+    QBoxLayout layout(QBoxLayout::TopToBottom, &widget);
+
+    QLabel *label1 = new QLabel("label1 text", &widget);
+    layout.addWidget(label1);
+    QLabel *label2 = new QLabel("label2 text", &widget);
+    layout.addWidget(label2);
+
+    widget.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&widget));
+    int normalHeight = widget.height();
+
+    // a. Verify that a removed visible will mean lesser size after adjust
+    label1->hide();
+    widget.adjustSize();
+    int heightWithoutLabel1 = widget.height();
+    QVERIFY(heightWithoutLabel1 < normalHeight);
+
+    // b restore with verify that the size is the same
+    label1->show();
+    QCOMPARE(widget.sizeHint().height(), normalHeight);
+
+    // c verify that a policy with retainSizeWhenHidden is respected
+    QSizePolicy sp_remove = label1->sizePolicy();
+    QSizePolicy sp_retain = label1->sizePolicy();
+    sp_retain.setRetainSizeWhenHidden(true);
+
+    label1->setSizePolicy(sp_retain);
+    label1->hide();
+    QCOMPARE(widget.sizeHint().height(), normalHeight);
+
+    // d check that changing the policy to not wanting size will result in lesser size
+    label1->setSizePolicy(sp_remove);
+    QCOMPARE(widget.sizeHint().height(), heightWithoutLabel1);
+
+    // e verify that changing back the hidden widget to want the hidden size will ensure that it gets more size
+    label1->setSizePolicy(sp_retain);
+    QCOMPARE(widget.sizeHint().height(), normalHeight);
+}
+
 QTEST_MAIN(tst_QLayout)
 #include "tst_qlayout.moc"
diff --git a/tests/manual/widgets/kernel/kernel.pro b/tests/manual/widgets/kernel/kernel.pro
index 4d26c9ee19..968d71724f 100644
--- a/tests/manual/widgets/kernel/kernel.pro
+++ b/tests/manual/widgets/kernel/kernel.pro
@@ -1,3 +1,2 @@
 TEMPLATE = subdirs
-SUBDIRS = qtooltip
-
+SUBDIRS = qtooltip sizeonhide
diff --git a/tests/manual/widgets/kernel/sizeonhide/main.cpp b/tests/manual/widgets/kernel/sizeonhide/main.cpp
new file mode 100644
index 0000000000..e8b95dfe28
--- /dev/null
+++ b/tests/manual/widgets/kernel/sizeonhide/main.cpp
@@ -0,0 +1,134 @@
+/****************************************************************************
+**
+** Copyright (C) 2013 Thorbjørn Martsum - tmartsum[at]gmail.com
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtWidgets module 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 <QtWidgets>
+
+class KeepSizeExampleDlg : public QDialog
+{
+    Q_OBJECT
+public:
+    QGridLayout *gridLayout;
+    QHBoxLayout *horizontalLayout;
+    QVBoxLayout *verticalLayout;
+    QCheckBox *checkBox;
+    QCheckBox *checkBox2;
+    QCheckBox *checkBox3;
+    QCheckBox *checkBox4;
+    QGroupBox *groupBox;
+    QVBoxLayout *verticalLayout2;
+    QRadioButton *radioButton;
+    QRadioButton *radioButton2;
+    QRadioButton *radioButton3;
+    QTableView *tableView;
+    QPushButton *pushButton;
+    QSpacerItem *horizontalSpacer;
+
+    KeepSizeExampleDlg()
+    {
+        QWidget *form = this;
+        form->resize(408, 295);
+        gridLayout = new QGridLayout(form);
+        horizontalLayout = new QHBoxLayout();
+        verticalLayout = new QVBoxLayout();
+        checkBox = new QCheckBox(form);
+        verticalLayout->addWidget(checkBox);
+        checkBox2 = new QCheckBox(form);
+        verticalLayout->addWidget(checkBox2);
+        checkBox3 = new QCheckBox(form);
+        verticalLayout->addWidget(checkBox3);
+        checkBox4 = new QCheckBox(form);
+        verticalLayout->addWidget(checkBox4);
+        horizontalLayout->addLayout(verticalLayout);
+        groupBox = new QGroupBox(form);
+        verticalLayout2 = new QVBoxLayout(groupBox);
+        radioButton = new QRadioButton(groupBox);
+        verticalLayout2->addWidget(radioButton);
+        radioButton2 = new QRadioButton(groupBox);
+        verticalLayout2->addWidget(radioButton2);
+        radioButton3 = new QRadioButton(groupBox);
+        verticalLayout2->addWidget(radioButton3);
+        horizontalLayout->addWidget(groupBox);
+        gridLayout->addLayout(horizontalLayout, 0, 0, 1, 2);
+        tableView = new QTableView(form);
+        gridLayout->addWidget(tableView, 1, 0, 1, 2);
+        pushButton = new QPushButton(form);
+        gridLayout->addWidget(pushButton, 2, 0, 1, 1);
+        horizontalSpacer = new QSpacerItem(340, 20, QSizePolicy::Expanding, QSizePolicy::Minimum);
+        gridLayout->addItem(horizontalSpacer, 2, 1, 1, 1);
+        checkBox->setText(QString::fromUtf8("CheckBox1"));
+        checkBox2->setText(QString::fromUtf8("CheckBox2"));
+        checkBox3->setText(QString::fromUtf8("CheckBox - for client A only"));
+        checkBox4->setText(QString::fromUtf8("CheckBox - also for client A"));
+        groupBox->setTitle(QString::fromUtf8("Mode"));
+        radioButton->setText(QString::fromUtf8("Mode 1"));
+        radioButton2->setText(QString::fromUtf8("Mode 2"));
+        radioButton3->setText(QString::fromUtf8("Mode 3"));
+        pushButton->setText(QString::fromUtf8("&Hide/Show"));
+
+        QObject::connect(pushButton, SIGNAL(clicked()), this, SLOT(showOrHide()));
+    }
+
+    protected slots:
+    void showOrHide()
+    {
+        if (checkBox3->isVisible()) {
+            checkBox3->hide();
+            checkBox4->hide();
+        } else {
+            checkBox3->show();
+            checkBox4->show();
+        }
+    }
+};
+
+int main(int argc, char *argv[])
+{
+    QApplication app(argc, argv);
+    KeepSizeExampleDlg d;
+    QSizePolicy policyKeepSpace = d.checkBox3->sizePolicy();
+    policyKeepSpace.setRetainSizeWhenHidden(true);
+    d.checkBox3->setSizePolicy(policyKeepSpace);
+    d.checkBox4->setSizePolicy(policyKeepSpace);
+    d.show();
+    app.exec();
+}
+
+#include "main.moc"
diff --git a/tests/manual/widgets/kernel/sizeonhide/sizeonhide.pro b/tests/manual/widgets/kernel/sizeonhide/sizeonhide.pro
new file mode 100644
index 0000000000..1969392ab3
--- /dev/null
+++ b/tests/manual/widgets/kernel/sizeonhide/sizeonhide.pro
@@ -0,0 +1,3 @@
+TEMPLATE = app
+SOURCES = main.cpp
+QT += widgets core-private