JUCE/modules/juce_gui_basics/widgets/juce_ListBox.cpp

/*
  ==============================================================================

   This file is part of the JUCE 6 technical preview.
   Copyright (c) 2020 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For this technical preview, this file is not subject to commercial licensing.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

class ListBox::RowComponent  : public Component,
                               public TooltipClient
{
public:
    RowComponent (ListBox& lb) : owner (lb) {}

    void paint (Graphics& g) override
    {
        if (auto* m = owner.getModel())
            m->paintListBoxItem (row, g, getWidth(), getHeight(), selected);
    }

    void update (const int newRow, const bool nowSelected)
    {
        if (row != newRow || selected != nowSelected)
        {
            repaint();
            row = newRow;
            selected = nowSelected;
        }

        if (auto* m = owner.getModel())
        {
            setMouseCursor (m->getMouseCursorForRow (row));

            customComponent.reset (m->refreshComponentForRow (newRow, nowSelected, customComponent.release()));

            if (customComponent != nullptr)
            {
                addAndMakeVisible (customComponent.get());
                customComponent->setBounds (getLocalBounds());
            }
        }
    }

    void performSelection (const MouseEvent& e, bool isMouseUp)
    {
        owner.selectRowsBasedOnModifierKeys (row, e.mods, isMouseUp);

        if (auto* m = owner.getModel())
            m->listBoxItemClicked (row, e);
    }

    bool isInDragToScrollViewport() const noexcept
    {
        if (auto* vp = owner.getViewport())
            return vp->isScrollOnDragEnabled() && (vp->canScrollVertically() || vp->canScrollHorizontally());

        return false;
    }

    void mouseDown (const MouseEvent& e) override
    {
        isDragging = false;
        isDraggingToScroll = false;
        selectRowOnMouseUp = false;

        if (isEnabled())
        {
            if (owner.selectOnMouseDown && ! (selected || isInDragToScrollViewport()))
                performSelection (e, false);
            else
                selectRowOnMouseUp = true;
        }
    }

    void mouseUp (const MouseEvent& e) override
    {
        if (isEnabled() && selectRowOnMouseUp && ! (isDragging || isDraggingToScroll))
            performSelection (e, true);
    }

    void mouseDoubleClick (const MouseEvent& e) override
    {
        if (isEnabled())
            if (auto* m = owner.getModel())
                m->listBoxItemDoubleClicked (row, e);
    }

    void mouseDrag (const MouseEvent& e) override
    {
        if (auto* m = owner.getModel())
        {
            if (isEnabled() && e.mouseWasDraggedSinceMouseDown() && ! isDragging)
            {
                SparseSet<int> rowsToDrag;

                if (owner.selectOnMouseDown || owner.isRowSelected (row))
                    rowsToDrag = owner.getSelectedRows();
                else
                    rowsToDrag.addRange (Range<int>::withStartAndLength (row, 1));

                if (rowsToDrag.size() > 0)
                {
                    auto dragDescription = m->getDragSourceDescription (rowsToDrag);

                    if (! (dragDescription.isVoid() || (dragDescription.isString() && dragDescription.toString().isEmpty())))
                    {
                        isDragging = true;
                        owner.startDragAndDrop (e, rowsToDrag, dragDescription, true);
                    }
                }
            }
        }

        if (! isDraggingToScroll)
            if (auto* vp = owner.getViewport())
                isDraggingToScroll = vp->isCurrentlyScrollingOnDrag();
    }

    void resized() override
    {
        if (customComponent != nullptr)
            customComponent->setBounds (getLocalBounds());
    }

    String getTooltip() override
    {
        if (auto* m = owner.getModel())
            return m->getTooltipForRow (row);

        return {};
    }

    ListBox& owner;
    std::unique_ptr<Component> customComponent;
    int row = -1;
    bool selected = false, isDragging = false, isDraggingToScroll = false, selectRowOnMouseUp = false;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (RowComponent)
};


//==============================================================================
class ListBox::ListViewport  : public Viewport
{
public:
    ListViewport (ListBox& lb)  : owner (lb)
    {
        setWantsKeyboardFocus (false);

        auto content = new Component();
        setViewedComponent (content);
        content->setWantsKeyboardFocus (false);
    }

    RowComponent* getComponentForRow (const int row) const noexcept
    {
        return rows [row % jmax (1, rows.size())];
    }

    RowComponent* getComponentForRowIfOnscreen (const int row) const noexcept
    {
        return (row >= firstIndex && row < firstIndex + rows.size())
                 ? getComponentForRow (row) : nullptr;
    }

    int getRowNumberOfComponent (Component* const rowComponent) const noexcept
    {
        const int index = getViewedComponent()->getIndexOfChildComponent (rowComponent);
        const int num = rows.size();

        for (int i = num; --i >= 0;)
            if (((firstIndex + i) % jmax (1, num)) == index)
                return firstIndex + i;

        return -1;
    }

    void visibleAreaChanged (const Rectangle<int>&) override
    {
        updateVisibleArea (true);

        if (auto* m = owner.getModel())
            m->listWasScrolled();
    }

    void updateVisibleArea (const bool makeSureItUpdatesContent)
    {
        hasUpdated = false;

        auto& content = *getViewedComponent();
        auto newX = content.getX();
        auto newY = content.getY();
        auto newW = jmax (owner.minimumRowWidth, getMaximumVisibleWidth());
        auto newH = owner.totalItems * owner.getRowHeight();

        if (newY + newH < getMaximumVisibleHeight() && newH > getMaximumVisibleHeight())
            newY = getMaximumVisibleHeight() - newH;

        content.setBounds (newX, newY, newW, newH);

        if (makeSureItUpdatesContent && ! hasUpdated)
            updateContents();
    }

    void updateContents()
    {
        hasUpdated = true;
        auto rowH = owner.getRowHeight();
        auto& content = *getViewedComponent();

        if (rowH > 0)
        {
            auto y = getViewPositionY();
            auto w = content.getWidth();

            const int numNeeded = 2 + getMaximumVisibleHeight() / rowH;
            rows.removeRange (numNeeded, rows.size());

            while (numNeeded > rows.size())
            {
                auto newRow = new RowComponent (owner);
                rows.add (newRow);
                content.addAndMakeVisible (newRow);
            }

            firstIndex = y / rowH;
            firstWholeIndex = (y + rowH - 1) / rowH;
            lastWholeIndex = (y + getMaximumVisibleHeight() - 1) / rowH;

            for (int i = 0; i < numNeeded; ++i)
            {
                const int row = i + firstIndex;

                if (auto* rowComp = getComponentForRow (row))
                {
                    rowComp->setBounds (0, row * rowH, w, rowH);
                    rowComp->update (row, owner.isRowSelected (row));
                }
            }
        }

        if (owner.headerComponent != nullptr)
            owner.headerComponent->setBounds (owner.outlineThickness + content.getX(),
                                              owner.outlineThickness,
                                              jmax (owner.getWidth() - owner.outlineThickness * 2,
                                                    content.getWidth()),
                                              owner.headerComponent->getHeight());
    }

    void selectRow (const int row, const int rowH, const bool dontScroll,
                    const int lastSelectedRow, const int totalRows, const bool isMouseClick)
    {
        hasUpdated = false;

        if (row < firstWholeIndex && ! dontScroll)
        {
            setViewPosition (getViewPositionX(), row * rowH);
        }
        else if (row >= lastWholeIndex && ! dontScroll)
        {
            const int rowsOnScreen = lastWholeIndex - firstWholeIndex;

            if (row >= lastSelectedRow + rowsOnScreen
                 && rowsOnScreen < totalRows - 1
                 && ! isMouseClick)
            {
                setViewPosition (getViewPositionX(),
                                 jlimit (0, jmax (0, totalRows - rowsOnScreen), row) * rowH);
            }
            else
            {
                setViewPosition (getViewPositionX(),
                                 jmax (0, (row  + 1) * rowH - getMaximumVisibleHeight()));
            }
        }

        if (! hasUpdated)
            updateContents();
    }

    void scrollToEnsureRowIsOnscreen (const int row, const int rowH)
    {
        if (row < firstWholeIndex)
        {
            setViewPosition (getViewPositionX(), row * rowH);
        }
        else if (row >= lastWholeIndex)
        {
            setViewPosition (getViewPositionX(),
                             jmax (0, (row  + 1) * rowH - getMaximumVisibleHeight()));
        }
    }

    void paint (Graphics& g) override
    {
        if (isOpaque())
            g.fillAll (owner.findColour (ListBox::backgroundColourId));
    }

    bool keyPressed (const KeyPress& key) override
    {
        if (Viewport::respondsToKey (key))
        {
            const int allowableMods = owner.multipleSelection ? ModifierKeys::shiftModifier : 0;

            if ((key.getModifiers().getRawFlags() & ~allowableMods) == 0)
            {
                // we want to avoid these keypresses going to the viewport, and instead allow
                // them to pass up to our listbox..
                return false;
            }
        }

        return Viewport::keyPressed (key);
    }

private:
    ListBox& owner;
    OwnedArray<RowComponent> rows;
    int firstIndex = 0, firstWholeIndex = 0, lastWholeIndex = 0;
    bool hasUpdated = false;

    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ListViewport)
};

//==============================================================================
struct ListBoxMouseMoveSelector  : public MouseListener
{
    ListBoxMouseMoveSelector (ListBox& lb) : owner (lb)
    {
        owner.addMouseListener (this, true);
    }

    ~ListBoxMouseMoveSelector() override
    {
        owner.removeMouseListener (this);
    }

    void mouseMove (const MouseEvent& e) override
    {
        auto pos = e.getEventRelativeTo (&owner).position.toInt();
        owner.selectRow (owner.getRowContainingPosition (pos.x, pos.y), true);
    }

    void mouseExit (const MouseEvent& e) override
    {
        mouseMove (e);
    }

    ListBox& owner;
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (ListBoxMouseMoveSelector)
};


//==============================================================================
ListBox::ListBox (const String& name, ListBoxModel* const m)
    : Component (name), model (m)
{
    viewport.reset (new ListViewport (*this));
    addAndMakeVisible (viewport.get());

    ListBox::setWantsKeyboardFocus (true);
    ListBox::colourChanged();
}

ListBox::~ListBox()
{
    headerComponent.reset();
    viewport.reset();
}

void ListBox::setModel (ListBoxModel* const newModel)
{
    if (model != newModel)
    {
        model = newModel;
        repaint();
        updateContent();
    }
}

void ListBox::setMultipleSelectionEnabled (bool b) noexcept         { multipleSelection = b; }
void ListBox::setClickingTogglesRowSelection (bool b) noexcept      { alwaysFlipSelection = b; }
void ListBox::setRowSelectedOnMouseDown (bool b) noexcept           { selectOnMouseDown = b; }

void ListBox::setMouseMoveSelectsRows (bool b)
{
    if (b)
    {
        if (mouseMoveSelector == nullptr)
            mouseMoveSelector.reset (new ListBoxMouseMoveSelector (*this));
    }
    else
    {
        mouseMoveSelector.reset();
    }
}

//==============================================================================
void ListBox::paint (Graphics& g)
{
    if (! hasDoneInitialUpdate)
        updateContent();

    g.fillAll (findColour (backgroundColourId));
}

void ListBox::paintOverChildren (Graphics& g)
{
    if (outlineThickness > 0)
    {
        g.setColour (findColour (outlineColourId));
        g.drawRect (getLocalBounds(), outlineThickness);
    }
}

void ListBox::resized()
{
    viewport->setBoundsInset (BorderSize<int> (outlineThickness + (headerComponent != nullptr ? headerComponent->getHeight() : 0),
                                               outlineThickness, outlineThickness, outlineThickness));

    viewport->setSingleStepSizes (20, getRowHeight());

    viewport->updateVisibleArea (false);
}

void ListBox::visibilityChanged()
{
    viewport->updateVisibleArea (true);
}

Viewport* ListBox::getViewport() const noexcept
{
    return viewport.get();
}

//==============================================================================
void ListBox::updateContent()
{
    hasDoneInitialUpdate = true;
    totalItems = (model != nullptr) ? model->getNumRows() : 0;

    bool selectionChanged = false;

    if (selected.size() > 0 && selected [selected.size() - 1] >= totalItems)
    {
        selected.removeRange ({ totalItems, std::numeric_limits<int>::max() });
        lastRowSelected = getSelectedRow (0);
        selectionChanged = true;
    }

    viewport->updateVisibleArea (isVisible());
    viewport->resized();

    if (selectionChanged && model != nullptr)
        model->selectedRowsChanged (lastRowSelected);
}

//==============================================================================
void ListBox::selectRow (int row, bool dontScroll, bool deselectOthersFirst)
{
    selectRowInternal (row, dontScroll, deselectOthersFirst, false);
}

void ListBox::selectRowInternal (const int row,
                                 bool dontScroll,
                                 bool deselectOthersFirst,
                                 bool isMouseClick)
{
    if (! multipleSelection)
        deselectOthersFirst = true;

    if ((! isRowSelected (row))
         || (deselectOthersFirst && getNumSelectedRows() > 1))
    {
        if (isPositiveAndBelow (row, totalItems))
        {
            if (deselectOthersFirst)
                selected.clear();

            selected.addRange ({ row, row + 1 });

            if (getHeight() == 0 || getWidth() == 0)
                dontScroll = true;

            viewport->selectRow (row, getRowHeight(), dontScroll,
                                 lastRowSelected, totalItems, isMouseClick);

            lastRowSelected = row;
            model->selectedRowsChanged (row);
        }
        else
        {
            if (deselectOthersFirst)
                deselectAllRows();
        }
    }
}

void ListBox::deselectRow (const int row)
{
    if (selected.contains (row))
    {
        selected.removeRange ({ row, row + 1 });

        if (row == lastRowSelected)
            lastRowSelected = getSelectedRow (0);

        viewport->updateContents();
        model->selectedRowsChanged (lastRowSelected);
    }
}

void ListBox::setSelectedRows (const SparseSet<int>& setOfRowsToBeSelected,
                               const NotificationType sendNotificationEventToModel)
{
    selected = setOfRowsToBeSelected;
    selected.removeRange ({ totalItems, std::numeric_limits<int>::max() });

    if (! isRowSelected (lastRowSelected))
        lastRowSelected = getSelectedRow (0);

    viewport->updateContents();

    if (model != nullptr && sendNotificationEventToModel == sendNotification)
        model->selectedRowsChanged (lastRowSelected);
}

SparseSet<int> ListBox::getSelectedRows() const
{
    return selected;
}

void ListBox::selectRangeOfRows (int firstRow, int lastRow, bool dontScrollToShowThisRange)
{
    if (multipleSelection && (firstRow != lastRow))
    {
        const int numRows = totalItems - 1;
        firstRow = jlimit (0, jmax (0, numRows), firstRow);
        lastRow  = jlimit (0, jmax (0, numRows), lastRow);

        selected.addRange ({ jmin (firstRow, lastRow),
                             jmax (firstRow, lastRow) + 1 });

        selected.removeRange ({ lastRow, lastRow + 1 });
    }

    selectRowInternal (lastRow, dontScrollToShowThisRange, false, true);
}

void ListBox::flipRowSelection (const int row)
{
    if (isRowSelected (row))
        deselectRow (row);
    else
        selectRowInternal (row, false, false, true);
}

void ListBox::deselectAllRows()
{
    if (! selected.isEmpty())
    {
        selected.clear();
        lastRowSelected = -1;

        viewport->updateContents();

        if (model != nullptr)
            model->selectedRowsChanged (lastRowSelected);
    }
}

void ListBox::selectRowsBasedOnModifierKeys (const int row,
                                             ModifierKeys mods,
                                             const bool isMouseUpEvent)
{
    if (multipleSelection && (mods.isCommandDown() || alwaysFlipSelection))
    {
        flipRowSelection (row);
    }
    else if (multipleSelection && mods.isShiftDown() && lastRowSelected >= 0)
    {
        selectRangeOfRows (lastRowSelected, row);
    }
    else if ((! mods.isPopupMenu()) || ! isRowSelected (row))
    {
        selectRowInternal (row, false, ! (multipleSelection && (! isMouseUpEvent) && isRowSelected (row)), true);
    }
}

int ListBox::getNumSelectedRows() const
{
    return selected.size();
}

int ListBox::getSelectedRow (const int index) const
{
    return (isPositiveAndBelow (index, selected.size()))
                ? selected [index] : -1;
}

bool ListBox::isRowSelected (const int row) const
{
    return selected.contains (row);
}

int ListBox::getLastRowSelected() const
{
    return isRowSelected (lastRowSelected) ? lastRowSelected : -1;
}

//==============================================================================
int ListBox::getRowContainingPosition (const int x, const int y) const noexcept
{
    if (isPositiveAndBelow (x, getWidth()))
    {
        const int row = (viewport->getViewPositionY() + y - viewport->getY()) / rowHeight;

        if (isPositiveAndBelow (row, totalItems))
            return row;
    }

    return -1;
}

int ListBox::getInsertionIndexForPosition (const int x, const int y) const noexcept
{
    if (isPositiveAndBelow (x, getWidth()))
        return jlimit (0, totalItems, (viewport->getViewPositionY() + y + rowHeight / 2 - viewport->getY()) / rowHeight);

    return -1;
}

Component* ListBox::getComponentForRowNumber (const int row) const noexcept
{
    if (auto* listRowComp = viewport->getComponentForRowIfOnscreen (row))
        return listRowComp->customComponent.get();

    return nullptr;
}

int ListBox::getRowNumberOfComponent (Component* const rowComponent) const noexcept
{
    return viewport->getRowNumberOfComponent (rowComponent);
}

Rectangle<int> ListBox::getRowPosition (int rowNumber, bool relativeToComponentTopLeft) const noexcept
{
    auto y = viewport->getY() + rowHeight * rowNumber;

    if (relativeToComponentTopLeft)
        y -= viewport->getViewPositionY();

    return { viewport->getX(), y,
             viewport->getViewedComponent()->getWidth(), rowHeight };
}

void ListBox::setVerticalPosition (const double proportion)
{
    auto offscreen = viewport->getViewedComponent()->getHeight() - viewport->getHeight();

    viewport->setViewPosition (viewport->getViewPositionX(),
                               jmax (0, roundToInt (proportion * offscreen)));
}

double ListBox::getVerticalPosition() const
{
    auto offscreen = viewport->getViewedComponent()->getHeight() - viewport->getHeight();

    return offscreen > 0 ? viewport->getViewPositionY() / (double) offscreen
                         : 0;
}

int ListBox::getVisibleRowWidth() const noexcept
{
    return viewport->getViewWidth();
}

void ListBox::scrollToEnsureRowIsOnscreen (const int row)
{
    viewport->scrollToEnsureRowIsOnscreen (row, getRowHeight());
}

//==============================================================================
bool ListBox::keyPressed (const KeyPress& key)
{
    const int numVisibleRows = viewport->getHeight() / getRowHeight();

    const bool multiple = multipleSelection
                            && lastRowSelected >= 0
                            && key.getModifiers().isShiftDown();

    if (key.isKeyCode (KeyPress::upKey))
    {
        if (multiple)
            selectRangeOfRows (lastRowSelected, lastRowSelected - 1);
        else
            selectRow (jmax (0, lastRowSelected - 1));
    }
    else if (key.isKeyCode (KeyPress::downKey))
    {
        if (multiple)
            selectRangeOfRows (lastRowSelected, lastRowSelected + 1);
        else
            selectRow (jmin (totalItems - 1, jmax (0, lastRowSelected + 1)));
    }
    else if (key.isKeyCode (KeyPress::pageUpKey))
    {
        if (multiple)
            selectRangeOfRows (lastRowSelected, lastRowSelected - numVisibleRows);
        else
            selectRow (jmax (0, jmax (0, lastRowSelected) - numVisibleRows));
    }
    else if (key.isKeyCode (KeyPress::pageDownKey))
    {
        if (multiple)
            selectRangeOfRows (lastRowSelected, lastRowSelected + numVisibleRows);
        else
            selectRow (jmin (totalItems - 1, jmax (0, lastRowSelected) + numVisibleRows));
    }
    else if (key.isKeyCode (KeyPress::homeKey))
    {
        if (multiple)
            selectRangeOfRows (lastRowSelected, 0);
        else
            selectRow (0);
    }
    else if (key.isKeyCode (KeyPress::endKey))
    {
        if (multiple)
            selectRangeOfRows (lastRowSelected, totalItems - 1);
        else
            selectRow (totalItems - 1);
    }
    else if (key.isKeyCode (KeyPress::returnKey) && isRowSelected (lastRowSelected))
    {
        if (model != nullptr)
            model->returnKeyPressed (lastRowSelected);
    }
    else if ((key.isKeyCode (KeyPress::deleteKey) || key.isKeyCode (KeyPress::backspaceKey))
               && isRowSelected (lastRowSelected))
    {
        if (model != nullptr)
            model->deleteKeyPressed (lastRowSelected);
    }
    else if (multipleSelection && key == KeyPress ('a', ModifierKeys::commandModifier, 0))
    {
        selectRangeOfRows (0, std::numeric_limits<int>::max());
    }
    else
    {
        return false;
    }

    return true;
}

bool ListBox::keyStateChanged (const bool isKeyDown)
{
    return isKeyDown
            && (KeyPress::isKeyCurrentlyDown (KeyPress::upKey)
                || KeyPress::isKeyCurrentlyDown (KeyPress::pageUpKey)
                || KeyPress::isKeyCurrentlyDown (KeyPress::downKey)
                || KeyPress::isKeyCurrentlyDown (KeyPress::pageDownKey)
                || KeyPress::isKeyCurrentlyDown (KeyPress::homeKey)
                || KeyPress::isKeyCurrentlyDown (KeyPress::endKey)
                || KeyPress::isKeyCurrentlyDown (KeyPress::returnKey));
}

void ListBox::mouseWheelMove (const MouseEvent& e, const MouseWheelDetails& wheel)
{
    bool eventWasUsed = false;

    if (wheel.deltaX != 0.0f && getHorizontalScrollBar().isVisible())
    {
        eventWasUsed = true;
        getHorizontalScrollBar().mouseWheelMove (e, wheel);
    }

    if (wheel.deltaY != 0.0f && getVerticalScrollBar().isVisible())
    {
        eventWasUsed = true;
        getVerticalScrollBar().mouseWheelMove (e, wheel);
    }

    if (! eventWasUsed)
        Component::mouseWheelMove (e, wheel);
}

void ListBox::mouseUp (const MouseEvent& e)
{
    if (e.mouseWasClicked() && model != nullptr)
        model->backgroundClicked (e);
}

//==============================================================================
void ListBox::setRowHeight (const int newHeight)
{
    rowHeight = jmax (1, newHeight);
    viewport->setSingleStepSizes (20, rowHeight);
    updateContent();
}

int ListBox::getNumRowsOnScreen() const noexcept
{
    return viewport->getMaximumVisibleHeight() / rowHeight;
}

void ListBox::setMinimumContentWidth (const int newMinimumWidth)
{
    minimumRowWidth = newMinimumWidth;
    updateContent();
}

int ListBox::getVisibleContentWidth() const noexcept            { return viewport->getMaximumVisibleWidth(); }

ScrollBar& ListBox::getVerticalScrollBar() const noexcept       { return viewport->getVerticalScrollBar(); }
ScrollBar& ListBox::getHorizontalScrollBar() const noexcept     { return viewport->getHorizontalScrollBar(); }

void ListBox::colourChanged()
{
    setOpaque (findColour (backgroundColourId).isOpaque());
    viewport->setOpaque (isOpaque());
    repaint();
}

void ListBox::parentHierarchyChanged()
{
    colourChanged();
}

void ListBox::setOutlineThickness (int newThickness)
{
    outlineThickness = newThickness;
    resized();
}

void ListBox::setHeaderComponent (std::unique_ptr<Component> newHeaderComponent)
{
    headerComponent = std::move (newHeaderComponent);
    addAndMakeVisible (headerComponent.get());
    ListBox::resized();
}

void ListBox::repaintRow (const int rowNumber) noexcept
{
    repaint (getRowPosition (rowNumber, true));
}

Image ListBox::createSnapshotOfRows (const SparseSet<int>& rows, int& imageX, int& imageY)
{
    Rectangle<int> imageArea;
    auto firstRow = getRowContainingPosition (0, viewport->getY());

    for (int i = getNumRowsOnScreen() + 2; --i >= 0;)
    {
        if (rows.contains (firstRow + i))
        {
            if (auto* rowComp = viewport->getComponentForRowIfOnscreen (firstRow + i))
            {
                auto pos = getLocalPoint (rowComp, Point<int>());

                imageArea = imageArea.getUnion ({ pos.x, pos.y, rowComp->getWidth(), rowComp->getHeight() });
            }
        }
    }

    imageArea = imageArea.getIntersection (getLocalBounds());
    imageX = imageArea.getX();
    imageY = imageArea.getY();

    auto listScale = Component::getApproximateScaleFactorForComponent (this);
    Image snapshot (Image::ARGB, roundToInt (imageArea.getWidth() * listScale), roundToInt (imageArea.getHeight() * listScale), true);

    for (int i = getNumRowsOnScreen() + 2; --i >= 0;)
    {
        if (rows.contains (firstRow + i))
        {
            if (auto* rowComp = viewport->getComponentForRowIfOnscreen (firstRow + i))
            {
                Graphics g (snapshot);
                g.setOrigin (getLocalPoint (rowComp, Point<int>()) - imageArea.getPosition());

                auto rowScale = Component::getApproximateScaleFactorForComponent (rowComp);

                if (g.reduceClipRegion (rowComp->getLocalBounds() * rowScale))
                {
                    g.beginTransparencyLayer (0.6f);
                    g.addTransform (AffineTransform::scale (rowScale));
                    rowComp->paintEntireComponent (g, false);
                    g.endTransparencyLayer();
                }
            }
        }
    }

    return snapshot;
}

void ListBox::startDragAndDrop (const MouseEvent& e, const SparseSet<int>& rowsToDrag, const var& dragDescription, bool allowDraggingToOtherWindows)
{
    if (auto* dragContainer = DragAndDropContainer::findParentDragContainerFor (this))
    {
        int x, y;
        auto dragImage = createSnapshotOfRows (rowsToDrag, x, y);

        auto p = Point<int> (x, y) - e.getEventRelativeTo (this).position.toInt();
        dragContainer->startDragging (dragDescription, this, dragImage, allowDraggingToOtherWindows, &p, &e.source);
    }
    else
    {
        // to be able to do a drag-and-drop operation, the listbox needs to
        // be inside a component which is also a DragAndDropContainer.
        jassertfalse;
    }
}

//==============================================================================
Component* ListBoxModel::refreshComponentForRow (int, bool, Component* existingComponentToUpdate)
{
    ignoreUnused (existingComponentToUpdate);
    jassert (existingComponentToUpdate == nullptr); // indicates a failure in the code that recycles the components
    return nullptr;
}

void ListBoxModel::listBoxItemClicked (int, const MouseEvent&) {}
void ListBoxModel::listBoxItemDoubleClicked (int, const MouseEvent&) {}
void ListBoxModel::backgroundClicked (const MouseEvent&) {}
void ListBoxModel::selectedRowsChanged (int) {}
void ListBoxModel::deleteKeyPressed (int) {}
void ListBoxModel::returnKeyPressed (int) {}
void ListBoxModel::listWasScrolled() {}
var ListBoxModel::getDragSourceDescription (const SparseSet<int>&)      { return {}; }
String ListBoxModel::getTooltipForRow (int)                             { return {}; }
MouseCursor ListBoxModel::getMouseCursorForRow (int)                    { return MouseCursor::NormalCursor; }

} // namespace juce