QAbstractItemView为截断的项显示ToolTip（使用事件过滤）

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#ifndef ATOOLTIPPER_H
#define ATOOLTIPPER_H

#include <QObject>

class AToolTipper : public QObject
{
    Q_OBJECT
public:
    explicit AToolTipper(QObject *parent = 0);
    
    virtual bool eventFilter(QObject *, QEvent *);

protected:
    bool headerViewEventFilter(QObject *, QEvent *);
};

#endif // ATOOLTIPPER_H

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#include "atooltipper.h"
#include <QHelpEvent>
#include <QAbstractItemView>
#include <QHeaderView>
#include <QTreeView>
#include <QTableView>
#include <QToolTip>

AToolTipper::AToolTipper(QObject *parent) :
    QObject(parent)
{
}

bool AToolTipper::eventFilter(QObject *obj, QEvent *event)
{
    if (event->type() == QEvent::ToolTip)
    {
        QAbstractItemView *view = qobject_cast<QAbstractItemView*>(obj->parent());
        if (!view)
        {
            return false;
        }

        QHeaderView *headerView = qobject_cast<QHeaderView*>(view);
        if (headerView)
        {
            return headerViewEventFilter(obj, event);
        }

        QHelpEvent *helpEvent = static_cast<QHelpEvent*>(event);
        QPoint pos = helpEvent->pos();
        QModelIndex index = view->indexAt(pos);
        if (!index.isValid())
        {
            return false;
        }

        QString itemText = view->model()->data(index).toString();

        // 图标处理
        QSize iconSize(0, 0);
        QIcon icon = view->model()->data(index, Qt::DecorationRole).value<QIcon>();
        if (!icon.isNull())
        {
            QList<QSize> listSize = icon.availableSizes();
            if (listSize.size() > 0)
            {
                iconSize.setWidth(listSize.at(0).width());
                iconSize.setHeight(listSize.at(0).height());
            }
        }

        // 计算列头高度
        int headerHeight = 0;
        int headerWidth = 0;
        QTreeView *treeView = qobject_cast<QTreeView*>(view);
        if (treeView)
        {
            headerHeight = treeView->header()->height();
        }
        else
        {
            QTableView *tableView = qobject_cast<QTableView*>(view);
            if (tableView)
            {
                headerHeight = tableView->horizontalHeader()->height();
                headerWidth = tableView->verticalHeader()->width();
            }
        }

        // 文本边距
        const int textMargin = view->style()->pixelMetric(QStyle::PM_FocusFrameHMargin) + 1;
        const int iconMargin = iconSize.width() > 0 ? (view->style()->pixelMetric(QStyle::PM_FocusFrameHMargin) + 1) : 0;
        QRect rect = view->visualRect(index);
        QRect textRect = rect.adjusted(textMargin + iconSize.width() + iconMargin * 2, 0, -textMargin, 0); //实际可用矩形

        QFontMetrics fm(view->font());
        int flags = view->model()->data(index, Qt::TextAlignmentRole).toInt();
        QSize itemTextSize = fm.boundingRect(textRect, flags | Qt::TextLongestVariant | Qt::TextWordWrap, itemText).size();

        if ((itemTextSize.width() > textRect.width() || itemTextSize.height() > textRect.height()) && !itemText.isEmpty())
        {
            // 指定tip的限定矩形
            rect.adjust(headerWidth, headerHeight, headerWidth, headerHeight);
            QToolTip::showText(helpEvent->globalPos(), itemText, view, rect);
        }
        else
        {
            QToolTip::hideText();
        }
        return true;
    }

    return false;
}

bool AToolTipper::headerViewEventFilter(QObject *obj, QEvent *event)
{
    if (event->type() == QEvent::ToolTip)
    {
        QHeaderView *headerView = qobject_cast<QHeaderView*>(obj->parent());
        if (!headerView)
        {
            return false;
        }

        QHelpEvent *helpEvent = static_cast<QHelpEvent*>(event);
        QPoint pos = helpEvent->pos();
        int index = headerView->logicalIndexAt(pos);
        if (index < 0)
        {
            return false;
        }

        QString itemText = headerView->model()->headerData(index, headerView->orientation()).toString();
        const int textMargin = headerView->style()->pixelMetric(QStyle::PM_FocusFrameHMargin) + 1;
        int rectWidth = headerView->sectionSize(index) - textMargin * 2;
        int rectHeight = headerView->sizeHint().height();

        QFontMetrics fm(headerView->font());        
        int flag = headerView->model()->headerData(index, headerView->orientation(), Qt::TextAlignmentRole).toInt();
        QSize itemTextSize = fm.size(flag, itemText);
        if ((itemTextSize.width() > rectWidth || itemTextSize.height() > rectHeight) && !itemText.isEmpty())
        {
            QToolTip::showText(helpEvent->globalPos(), itemText, headerView);
        }
        else
        {
            QToolTip::hideText();
        }
        return true;
    }

    return false;
}

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tableView->viewport()->installEventFilter(new AToolTipper(tableView));
tableView->horizontalHeader()->viewport()->installEventFilter(new AToolTipper(tableView->horizontalHeader()));