Qtextedit边沿触发 用C++

如果您使用的是C++编写的Qt程序，可以使用类似的方法来检测QTextEdit的边沿触发事件。以下是一个示例：

#include <QTextEdit>
#include <QApplication>
#include <QEvent>
#include <QTextCursor>
#include <QPoint>

class MyTextEdit : public QTextEdit {
public:
    MyTextEdit(QWidget *parent = nullptr) : QTextEdit(parent) {
        setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
        setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
        setLineWrapMode(QTextEdit::NoWrap);
    }

    bool event(QEvent *event) override {
        if (event->type() == QEvent::MouseMove) {
            QTextCursor cursor = cursorForPosition(static_cast<QMouseEvent *>(event)->pos());
            if (cursor.atStart() || cursor.atEnd()) {
                QApplication::setOverrideCursor(Qt::ArrowCursor);
                return true;
            }
        }
        return QTextEdit::event(event);
    }

    void mousePressEvent(QMouseEvent *event) override {
        if (event->button() == Qt::LeftButton) {
            QTextCursor cursor = cursorForPosition(event->pos());
            if (cursor.atStart()) {
                setTextCursor(cursor);
                QApplication::setOverrideCursor(Qt::SizeHorCursor);
                m_drag_start_x = event->pos().x();
                return;
            } else if (cursor.atEnd()) {
                setTextCursor(cursor);
                QApplication::setOverrideCursor(Qt::SizeHorCursor);
                m_drag_start_x = event->pos().x();
                return;
            }
        }
        QTextEdit::mousePressEvent(event);
    }

    void mouseMoveEvent(QMouseEvent *event) override {
        if (event->buttons() & Qt::LeftButton) {
            int diff = event->pos().x() - m_drag_start_x;
            QTextCursor cursor = textCursor();
            if (cursor.atStart()) {
                if (diff < 0) {
                    return;
                }
                cursor.movePosition(QTextCursor::Left, QTextCursor::KeepAnchor);
            } else if (cursor.atEnd()) {
                if (diff > 0) {
                    return;
                }
                cursor.movePosition(QTextCursor::Right, QTextCursor::KeepAnchor);
            } else {
                return;
            }
            setTextCursor(cursor);
            m_drag_start_x = event->pos().x();
        } else {
            QTextEdit::mouseMoveEvent(event);
        }
    }

    void mouseReleaseEvent(QMouseEvent *event) override {
        if (event->button() == Qt::LeftButton) {
            QApplication::restoreOverrideCursor();
        }
        QTextEdit::mouseReleaseEvent(event);
    }

private:
    int m_drag_start_x = 0;
};

这段代码会在鼠标移动到文本编辑器的边缘时显示一个箭头光标，并且在鼠标按下并拖动边缘时，会使文本编辑器的宽度相应地增加或减少。