qt-creator/src/libs/utils/layoutbuilder.cpp

// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0

#include "layoutbuilder.h"

#include "qtcassert.h"

#include <QFormLayout>
#include <QGridLayout>
#include <QGroupBox>
#include <QLabel>
#include <QPushButton>
#include <QStackedLayout>
#include <QSplitter>
#include <QStyle>
#include <QTabWidget>
#include <QTextEdit>

namespace Layouting {

/*!
    \enum Utils::LayoutBuilder::LayoutType
    \inmodule QtCreator

    The LayoutType enum describes the type of \c QLayout a layout builder
    operates on.

    \value Form
    \value Grid
    \value HBox
    \value VBox
*/

/*!
    \class Utils::LayoutBuilder::LayoutItem
    \inmodule QtCreator

    \brief The LayoutItem class represents widgets, layouts, and aggregate
    items for use in conjunction with layout builders.

    Layout items are typically implicitly constructed when adding items to a
    \c LayoutBuilder instance using \c LayoutBuilder::addItem() or
    \c LayoutBuilder::addItems() and never stored in user code.
*/

/*!
    Constructs a layout item instance representing an empty cell.
 */
LayoutItem::LayoutItem()
{}


/*!
    \fn  template <class T> LayoutItem(const T &t)

    Constructs a layout item proxy for \a t.

    T could be
    \list
    \li  \c {QString}
    \li  \c {QWidget *}
    \li  \c {QLayout *}
    \endlist
 */


/*!
    Constructs a layout item representing something that knows how to add it
    to a layout by itself.
 */
QLayout *LayoutBuilder::createLayout() const
{
    QLayout *layout = nullptr;
    switch (m_layoutType) {
    case LayoutBuilder::FormLayout: {
        auto formLayout = new QFormLayout;
        formLayout->setFieldGrowthPolicy(QFormLayout::AllNonFixedFieldsGrow);
        layout = formLayout;
        break;
    }
    case LayoutBuilder::GridLayout: {
        auto gridLayout = new QGridLayout;
        layout = gridLayout;
        break;
    }
    case LayoutBuilder::HBoxLayout: {
        auto hboxLayout = new QHBoxLayout;
        layout = hboxLayout;
        break;
    }
    case LayoutBuilder::VBoxLayout: {
        auto vboxLayout = new QVBoxLayout;
        layout = vboxLayout;
        break;
    }
    case LayoutBuilder::StackLayout: {
        auto stackLayout = new QStackedLayout;
        layout = stackLayout;
        break;
    }
    }
    QTC_ASSERT(layout, return nullptr);
    if (m_spacing)
        layout->setSpacing(*m_spacing);
    return layout;
}

static QWidget *widgetForItem(QLayoutItem *item)
{
    if (QWidget *w = item->widget())
        return w;
    if (item->spacerItem())
        return nullptr;
    QLayout *l = item->layout();
    if (!l)
        return nullptr;
    for (int i = 0, n = l->count(); i < n; ++i) {
        if (QWidget *w = widgetForItem(l->itemAt(i)))
            return w;
    }
    return nullptr;
}

static QLabel *createLabel(const QString &text)
{
    auto label = new QLabel(text);
    label->setTextInteractionFlags(Qt::TextSelectableByMouse);
    return label;
}

static void addItemToBoxLayout(QBoxLayout *layout, const LayoutItem &item)
{
    if (QWidget *w = item.widget) {
        layout->addWidget(w);
    } else if (QLayout *l = item.layout) {
        layout->addLayout(l);
    } else if (item.specialType == LayoutItem::SpecialType::Stretch) {
        layout->addStretch(item.specialValue.toInt());
    } else if (item.specialType == LayoutItem::SpecialType::Space) {
        layout->addSpacing(item.specialValue.toInt());
    } else if (item.specialType == LayoutItem::SpecialType::HorizontalRule) {
        layout->addWidget(Layouting::createHr());
    } else if (!item.text.isEmpty()) {
        layout->addWidget(createLabel(item.text));
    } else {
        QTC_CHECK(false);
    }
}

static void flushPendingFormItems(QFormLayout *formLayout,
                                  LayoutBuilder::LayoutItems &pendingFormItems)
{
    QTC_ASSERT(formLayout, return);

    if (pendingFormItems.empty())
        return;

    // If there are more than two items, we cram the last ones in one hbox.
    if (pendingFormItems.size() > 2) {
        auto hbox = new QHBoxLayout;
        hbox->setContentsMargins(0, 0, 0, 0);
        for (int i = 1; i < pendingFormItems.size(); ++i)
            addItemToBoxLayout(hbox, pendingFormItems.at(i));
        while (pendingFormItems.size() >= 2)
            pendingFormItems.pop_back();
        pendingFormItems.append(LayoutItem(hbox));
    }

    if (pendingFormItems.size() == 1) { // One one item given, so this spans both columns.
        if (auto layout = pendingFormItems.at(0).layout)
            formLayout->addRow(layout);
        else if (auto widget = pendingFormItems.at(0).widget)
            formLayout->addRow(widget);
    } else if (pendingFormItems.size() == 2) { // Normal case, both columns used.
        if (auto label = pendingFormItems.at(0).widget) {
            if (auto layout = pendingFormItems.at(1).layout)
                formLayout->addRow(label, layout);
            else if (auto widget = pendingFormItems.at(1).widget)
                formLayout->addRow(label, widget);
        } else  {
            if (auto layout = pendingFormItems.at(1).layout)
                formLayout->addRow(pendingFormItems.at(0).text, layout);
            else if (auto widget = pendingFormItems.at(1).widget)
                formLayout->addRow(pendingFormItems.at(0).text, widget);
        }
    } else {
        QTC_CHECK(false);
    }

    // Set up label as buddy if possible.
    const int lastRow = formLayout->rowCount() - 1;
    QLayoutItem *l = formLayout->itemAt(lastRow, QFormLayout::LabelRole);
    QLayoutItem *f = formLayout->itemAt(lastRow, QFormLayout::FieldRole);
    if (l && f) {
        if (QLabel *label = qobject_cast<QLabel *>(l->widget())) {
            if (QWidget *widget = widgetForItem(f))
                label->setBuddy(widget);
        }
    }

    pendingFormItems.clear();
}

static void doLayoutHelper(QLayout *layout,
                           const LayoutBuilder::LayoutItems &items,
                           const Layouting::AttachType attachType,
                           int currentGridRow = 0)
{
    int currentGridColumn = 0;
    LayoutBuilder::LayoutItems pendingFormItems;

    auto formLayout = qobject_cast<QFormLayout *>(layout);
    auto gridLayout = qobject_cast<QGridLayout *>(layout);
    auto boxLayout = qobject_cast<QBoxLayout *>(layout);
    auto stackLayout = qobject_cast<QStackedLayout *>(layout);

    for (const LayoutItem &item : items) {
        if (item.specialType == LayoutItem::SpecialType::Break) {
            if (formLayout)
                flushPendingFormItems(formLayout, pendingFormItems);
            else if (gridLayout) {
                if (currentGridColumn != 0) {
                    ++currentGridRow;
                    currentGridColumn = 0;
                }
            }
            continue;
        }

        QWidget *widget = item.widget;

        if (gridLayout) {
            Qt::Alignment align = {};
            if (attachType == Layouting::WithFormAlignment && currentGridColumn == 0)
                align = Qt::Alignment(widget->style()->styleHint(QStyle::SH_FormLayoutLabelAlignment));
            if (widget)
                gridLayout->addWidget(widget, currentGridRow, currentGridColumn, 1, item.span, align);
            else if (item.layout)
                gridLayout->addLayout(item.layout, currentGridRow, currentGridColumn, 1, item.span, align);
            else if (!item.text.isEmpty())
                gridLayout->addWidget(createLabel(item.text), currentGridRow, currentGridColumn, 1, 1, align);
            currentGridColumn += item.span;
        } else if (boxLayout) {
            addItemToBoxLayout(boxLayout, item);
        } else if (stackLayout) {
            stackLayout->addWidget(item.widget);
        } else {
            pendingFormItems.append(item);
        }
    }

    if (formLayout)
        flushPendingFormItems(formLayout, pendingFormItems);
}


/*!
    Constructs a layout item from the contents of another LayoutBuilder
 */
void LayoutItem::setBuilder(const LayoutBuilder &builder)
{
    layout = builder.createLayout();
    doLayoutHelper(layout, builder.m_items, Layouting::WithoutMargins);
}

/*!
    \class Utils::LayoutBuilder::Space
    \inmodule QtCreator

    \brief The LayoutBuilder::Space class represents some empty space in a layout.
 */

/*!
    \class Utils::LayoutBuilder::Stretch
    \inmodule QtCreator

    \brief The LayoutBuilder::Stretch class represents some stretch in a layout.
 */

/*!
    \class Utils::LayoutBuilder
    \inmodule QtCreator

    \brief The LayoutBuilder class provides a convenient way to fill \c QFormLayout
    and \c QGridLayouts with contents.

    Filling a layout with items happens item-by-item, row-by-row.

    A LayoutBuilder instance is typically used locally within a function and never stored.

    \sa addItem(), addItems(), addRow(), finishRow()
*/

LayoutBuilder::LayoutBuilder(LayoutType layoutType, const LayoutItems &items)
    : m_layoutType(layoutType)
{
    m_items.reserve(items.size() * 2);
    for (const LayoutItem &item : items)
        addItem(item);
}

LayoutBuilder &LayoutBuilder::setSpacing(int spacing)
{
    m_spacing = spacing;
    return *this;
}

LayoutBuilder::LayoutBuilder() = default;

/*!
    Destructs a layout builder.
 */
LayoutBuilder::~LayoutBuilder() = default;

/*!
    Instructs a layout builder to finish the current row.
    This is implicitly called by LayoutBuilder's destructor.
 */
LayoutBuilder &LayoutBuilder::finishRow()
{
    addItem(Break());
    return *this;
}

/*!
    This starts a new row containing \a items. The row can be further extended by
    other items using \c addItem() or \c addItems().

    \sa finishRow(), addItem(), addItems()
 */
LayoutBuilder &LayoutBuilder::addRow(const LayoutItems &items)
{
    return finishRow().addItems(items);
}

/*!
    Adds the layout item \a item to the current row.
 */
LayoutBuilder &LayoutBuilder::addItem(const LayoutItem &item)
{
    if (item.onAdd) {
        item.onAdd(*this);
    } else {
        m_items.push_back(item);
    }
    return *this;
}

void LayoutBuilder::doLayout(QWidget *parent, Layouting::AttachType attachType) const
{
    QLayout *layout = createLayout();
    parent->setLayout(layout);

    doLayoutHelper(layout, m_items, attachType);
    if (attachType == Layouting::WithoutMargins)
        layout->setContentsMargins(0, 0, 0, 0);
}

/*!
    Adds the layout item \a items to the current row.
 */
LayoutBuilder &LayoutBuilder::addItems(const LayoutItems &items)
{
    for (const LayoutItem &item : items)
        addItem(item);
    return *this;
}

/*!
    Attach the constructed layout to the provided \c QWidget \a parent.

    This operation can only be performed once per LayoutBuilder instance.
 */
void LayoutBuilder::attachTo(QWidget *w, Layouting::AttachType attachType) const
{
    doLayout(w, attachType);
}

QWidget *LayoutBuilder::emerge(Layouting::AttachType attachType)
{
    auto w = new QWidget;
    doLayout(w, attachType);
    return w;
}

/*!
    Constructs a layout extender to extend an existing \a layout.

    This constructor can be used to continue the work of previous layout building.
    The type of the underlying layout and previous contents will be retained,
    new items will be added below existing ones.
 */

LayoutExtender::LayoutExtender(QLayout *layout, Layouting::AttachType attachType)
    : m_layout(layout), m_attachType(attachType)
{}

LayoutExtender::~LayoutExtender()
{
    QTC_ASSERT(m_layout, return);
    int currentGridRow = 0;
    if (auto gridLayout = qobject_cast<QGridLayout *>(m_layout))
        currentGridRow = gridLayout->rowCount();
    doLayoutHelper(m_layout, m_items, m_attachType, currentGridRow);
}

// Special items

Tab::Tab(const QString &tabName, const LayoutBuilder &item)
{
    text = tabName;
    widget = new QWidget;
    item.attachTo(widget);
}

// "Widgets"

static void applyItems(QWidget *widget, const QList<LayoutItem> &items)
{
    bool hadLayout = false;
    for (const LayoutItem &item : items) {
        if (item.setter) {
            item.setter(widget);
        } else if (item.layout && !hadLayout) {
            hadLayout = true;
            widget->setLayout(item.layout);
        } else {
            QTC_CHECK(false);
        }
    }
}

Group::Group(std::initializer_list<LayoutItem> items)
{
    widget = new QGroupBox;
    applyItems(widget, items);
}

PushButton::PushButton(std::initializer_list<LayoutItem> items)
{
    widget = new QPushButton;
    applyItems(widget, items);
}

TextEdit::TextEdit(std::initializer_list<LayoutItem> items)
{
    widget = new QTextEdit;
    applyItems(widget, items);
}

Splitter::Splitter(std::initializer_list<LayoutItem> items)
    : Splitter(new QSplitter(Qt::Vertical), items) {}

Splitter::Splitter(QSplitter *splitter, std::initializer_list<LayoutItem> items)
{
    widget = splitter;
    for (const LayoutItem &item : items)
        splitter->addWidget(item.widget);
}

TabWidget::TabWidget(std::initializer_list<Tab> tabs)
    : TabWidget(new QTabWidget, tabs) {}

TabWidget::TabWidget(QTabWidget *tabWidget, std::initializer_list<Tab> tabs)
{
    widget = tabWidget;
    for (const Tab &tab : tabs)
        tabWidget->addTab(tab.widget, tab.text);
}

// "Properties"

LayoutItem::Setter title(const QString &title)
{
    return [title](QObject *target) {
        if (auto groupBox = qobject_cast<QGroupBox *>(target)) {
            groupBox->setTitle(title);
            groupBox->setObjectName(title);
        } else {
            QTC_CHECK(false);
        }
    };
}

LayoutItem::Setter onClicked(const std::function<void ()> &func, QObject *guard)
{
    return [func, guard](QObject *target) {
        if (auto button = qobject_cast<QAbstractButton *>(target)) {
            QObject::connect(button, &QAbstractButton::clicked, guard ? guard : target, func);
        } else {
            QTC_CHECK(false);
        }
    };
}

LayoutItem::Setter text(const QString &text)
{
    return [text](QObject *target) {
        if (auto button = qobject_cast<QAbstractButton *>(target)) {
            button->setText(text);
        } else if (auto textEdit = qobject_cast<QTextEdit *>(target)) {
            textEdit->setText(text);
        } else {
            QTC_CHECK(false);
        }
    };
}

LayoutItem::Setter tooltip(const QString &toolTip)
{
    return [toolTip](QObject *target) {
        if (auto widget = qobject_cast<QWidget *>(target)) {
            widget->setToolTip(toolTip);
        } else {
            QTC_CHECK(false);
        }
    };
}

QWidget *createHr(QWidget *parent)
{
    auto frame = new QFrame(parent);
    frame->setFrameShape(QFrame::HLine);
    frame->setFrameShadow(QFrame::Sunken);
    return frame;
}

// Singletons.
Break br;
Stretch st;
Space empty(0);
HorizontalRule hr;

} // Layouting