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**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of Qt Creator.
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** accordance with the commercial license agreement provided with the
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** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 as published by the Free Software
** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
** included in the packaging of this file. Please review the following
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#include "highlightscrollbar.h"

#include <utils/qtcassert.h>

#include <QPainter>
#include <QResizeEvent>
#include <QStyle>
#include <QStyleOptionSlider>
#include <QTimer>

using namespace Core;
using namespace Utils;

HighlightScrollBar::HighlightScrollBar(Qt::Orientation orientation, QWidget *parent)
    : QScrollBar(orientation, parent)
    , m_widget(parent)
    , m_overlay(new HighlightScrollBarOverlay(this))
{
    connect(m_overlay, &HighlightScrollBarOverlay::destroyed,
            this, &HighlightScrollBar::overlayDestroyed);
    // valueChanged(0) flashes transient scroll bars, which is needed
    // for a correct initialization.
    emit valueChanged(0);
}

HighlightScrollBar::~HighlightScrollBar()
{
    if (!m_overlay || m_overlay->parent() == this)
        return;

    delete m_overlay;
}

void HighlightScrollBar::setVisibleRange(float visibleRange)
{
    if (!m_overlay)
        return;
    m_overlay->m_visibleRange = visibleRange;
}

void HighlightScrollBar::setRangeOffset(float offset)
{
    if (!m_overlay)
        return;
    m_overlay->m_offset = offset;
}

void HighlightScrollBar::setColor(Id category, Theme::Color color)
{
    if (!m_overlay)
        return;
    m_overlay->m_colors[category] = color;
}

QRect HighlightScrollBar::overlayRect()
{
    QStyleOptionSlider opt;
    initStyleOption(&opt);
    return style()->subControlRect(QStyle::CC_ScrollBar, &opt, QStyle::SC_ScrollBarGroove, this);
}

void HighlightScrollBar::overlayDestroyed()
{
    m_overlay = 0;
}

void HighlightScrollBar::setPriority(Id category, HighlightScrollBar::Priority prio)
{
    if (!m_overlay)
        return;
    m_overlay->m_priorities[category] = prio;
    m_overlay->scheduleUpdate();
}

void HighlightScrollBar::addHighlights(Id category, QSet<int> highlights)
{
    if (!m_overlay)
        return;
    m_overlay->m_highlights[category].unite(highlights);
    m_overlay->scheduleUpdate();
}

void HighlightScrollBar::addHighlight(Id category, int highlight)
{
    if (!m_overlay)
        return;
    m_overlay->m_highlights[category] << highlight;
    m_overlay->scheduleUpdate();
}

void HighlightScrollBar::removeHighlights(Id category)
{
    if (!m_overlay)
        return;
    m_overlay->m_highlights.remove(category);
    m_overlay->scheduleUpdate();
}

void HighlightScrollBar::removeAllHighlights()
{
    if (!m_overlay)
        return;
    m_overlay->m_highlights.clear();
    m_overlay->scheduleUpdate();
}

bool HighlightScrollBar::eventFilter(QObject *obj, QEvent *event)
{
    if (obj == m_widget && m_overlay && m_widget == m_overlay->parent() &&
            (event->type() == QEvent::Resize || event->type() == QEvent::Move)) {
        QStyleOptionSlider opt;
        initStyleOption(&opt);
        const int width = style()->pixelMetric(QStyle::PM_ScrollBarExtent, &opt, this);
        m_overlay->move(m_widget->width() - width, 0);
        resize(width, m_widget->height());
    }
    return false;
}

void HighlightScrollBar::resizeEvent(QResizeEvent *event)
{
    if (!m_overlay)
        return;
    QScrollBar::resizeEvent(event);
    m_overlay->resize(size());
}

void HighlightScrollBar::moveEvent(QMoveEvent *event)
{
    if (!m_overlay)
        return;
    QScrollBar::moveEvent(event);
    m_overlay->adjustPosition();
}

void HighlightScrollBar::showEvent(QShowEvent *event)
{
    if (!m_overlay)
        return;
    QScrollBar::showEvent(event);
    if (parentWidget() != this) {
        m_widget->removeEventFilter(this);
        m_overlay->setParent(this);
        m_overlay->adjustPosition();
        m_overlay->show();
    }
}

void HighlightScrollBar::hideEvent(QHideEvent *event)
{
    if (!m_overlay)
        return;
    QScrollBar::hideEvent(event);
    if (parentWidget() != m_widget) {
        m_widget->installEventFilter(this);
        m_overlay->setParent(m_widget);
        m_overlay->adjustPosition();
        m_overlay->show();
    }
}

void HighlightScrollBar::changeEvent(QEvent *event)
{
    // Workaround for QTBUG-45579
    if (event->type() == QEvent::ParentChange)
        setStyle(style());
}

void HighlightScrollBarOverlay::scheduleUpdate()
{
    if (m_cacheUpdateScheduled)
        return;

    m_cacheUpdateScheduled = true;
    QTimer::singleShot(0, this, static_cast<void (QWidget::*)()>(&QWidget::update));
}

void HighlightScrollBarOverlay::updateCache()
{
    if (!m_cacheUpdateScheduled)
        return;

    m_cache.clear();
    foreach (const Id &category, m_highlights.keys()) {
        foreach (const int &highlight, m_highlights[category]) {
            Id highlightCategory = m_cache[highlight];
            if (highlightCategory.isValid() && (m_priorities[highlightCategory] >= m_priorities[category]))
                continue;
            m_cache[highlight] = category;
        }
    }
    m_cacheUpdateScheduled = false;
}

void HighlightScrollBarOverlay::adjustPosition()
{
    move(parentWidget()->mapFromGlobal(m_scrollBar->mapToGlobal(m_scrollBar->pos())));
}

void HighlightScrollBarOverlay::paintEvent(QPaintEvent *paintEvent)
{
    QWidget::paintEvent(paintEvent);

    updateCache();

    if (m_cache.isEmpty())
        return;

    const QRect &rect = m_scrollBar->overlayRect();

    Id previousCategory;
    QRect *previousRect = 0;

    const int scrollbarRange = m_scrollBar->maximum() + m_scrollBar->pageStep();
    const int range = qMax(m_visibleRange, float(scrollbarRange));
    const int horizontalMargin = 3;
    const int resultWidth = rect.width() - 2 * horizontalMargin + 1;
    const int resultHeight = qMin(int(rect.height() / range) + 1, 4);
    const int offset = rect.height() / range * m_offset;
    const int verticalMargin = ((rect.height() / range) - resultHeight) / 2;
    int previousBottom = -1;

    QHash<Id, QVector<QRect> > highlights;
    QMapIterator<int, Id> it(m_cache);
    while (it.hasNext()) {
        const Id currentCategory = it.next().value();

        // Calculate start and end
        int top = rect.top() + offset + verticalMargin + float(it.key()) / range * rect.height();
        const int bottom = top + resultHeight;

        if (QTC_GUARD(previousRect) && previousCategory == currentCategory && previousBottom + 1 >= top) {
            // If the previous highlight has the same category and is directly prior to this highlight
            // we just extend the previous highlight.
            previousRect->setBottom(bottom - 1);

        } else { // create a new highlight
            if (previousRect && previousBottom >= top) {
                // make sure that highlights with higher priority are drawn on top of other highlights
                // when rectangles are overlapping

                if (m_priorities[previousCategory] > m_priorities[currentCategory]) {
                    // Moving the top of the current highlight when the previous
                    // highlight has a higher priority
                    top = previousBottom + 1;
                    if (top == bottom) // if this would result in an empty highlight just skip
                        continue;
                } else {
                    previousRect->setBottom(top - 1); // move the end of the last highlight
                    if (previousRect->height() == 0) // if the result is an empty rect, remove it.
                        highlights[previousCategory].removeLast();
                }
            }
            highlights[currentCategory] << QRect(rect.left() + horizontalMargin, top,
                                                  resultWidth, bottom - top);
            previousRect = &highlights[currentCategory].last();
            previousCategory = currentCategory;
        }
        previousBottom = previousRect->bottom();
    }

    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, false);
    foreach (Id category, highlights.keys()) {
        const QColor &color = creatorTheme()->color(m_colors[category]);
        for (int i = 0, total = highlights[category].size(); i < total; ++i) {
            const QRect rect = highlights[category][i];
            painter.fillRect(rect, color);
        }
    }
}