To see what I mean do the following steps:

• open in some browser (i use Firefox) https://en.wikipedia.org/wiki/Test
• copy the incomplete line "To make test edits on Wikipedia, please use the san"
  ==> Important here: stop the selection in the middle of the link!
• paste that line into the QTextWidget (you can also use drag & drop)
• click on the button "Clear"
  ==> the widget still thinks it is in the middle of a link.

How can I reset this?

I tried to set a new QTextDocument, but this dows not clear too.
I tried to turn of acceptRichText before setting the new plain text and turning it on afterwards, did not help.

Any idea?

Attached is a minimal example (compile in gcc with -std=c++11).

#include "QtCore/qdebug.h"
#include "QtWidgets/qapplication.h"
#include "QtWidgets/qwidget.h"
#include "QtWidgets/qboxlayout.h"
#include "QtWidgets/qtextedit.h"
#include "QtWidgets/qtoolbutton.h"

class Widget : public QWidget {
public:
  Widget() {
    QHBoxLayout *l = new QHBoxLayout(this);
    edit = new QTextEdit(this);
    edit->setAcceptDrops(true);
    QToolButton *button = new QToolButton(this);
    button->setText("Clear");
    l->addWidget(edit);
    l->addWidget(button);
    connect(button, &QToolButton::clicked, [this] (bool checked) { edit->setPlainText("I am plain text"); });
  }
  QTextEdit *edit;
};

int main(int argc, char **argv) {
  QApplication app(argc, argv);
  Widget w;
  w.show();
  app.exec();
  return 0;
}