父函数终止每当我试图调用QTextCharFormat上的QTextCursor选择

Question

我最近遇到了一个奇怪的问题，每当调用QTextCursor::mergeCharFormat/setCharFormat/setBlockCharFormat时，我的QPlainTextEdit::selectionChanged处理程序函数就会过早终止。此外，在终止之后，它被再次调用，并遇到同样的问题，导致无限循环。

我正在尝试复制许多文本编辑器(如notepad++)中存在的功能，当选择一个单词时，整个文档中所有相似的单词都会突出显示。我的TextEditor类从QPlainTextEdit过载。

最小可复制示例如下:

main.cpp:

#include "mainWindow.h"
#include <QtWidgets/QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
mainWindow w;
w.show();
return a.exec();
}

MainWindow.h:

#pragma once
#include <QtWidgets/QMainWindow>
#include "ui_mainWindow.h"
#include "TextEditor.h"
class mainWindow : public QMainWindow
{
Q_OBJECT
public:
mainWindow(QWidget *parent = Q_NULLPTR) : QMainWindow(parent)
{
ui.setupUi(this);
auto textEdit = new TextEditor(this);
textEdit->setPlainText("test lorem ipsum testn dolor sit test");
ui.tabWidget->addTab(textEdit, "Editor"); //Or any other way of adding the widget to the window
}
private:
Ui::mainWindowClass ui;
};

TextEditor.h:

regex荧光笔部分是基于这个SO答案。

#pragma once
#include <QPlainTextEdit>
class TextEditor : public QPlainTextEdit
{
Q_OBJECT
public:
TextEditor(QWidget* parent) : QPlainTextEdit(parent)
{
connect(this, &QPlainTextEdit::selectionChanged, this, &TextEditor::selectChangeHandler);
}
private:
void selectChangeHandler()
{
//Ignore empty selections
if (textCursor().selectionStart() >= textCursor().selectionEnd())
return;
//We only care about fully selected words (nonalphanumerical characters on either side of selection)
auto plaintext = toPlainText();
auto prevChar = plaintext.mid(textCursor().selectionStart() - 1, 1).toStdString()[0];
auto nextChar = plaintext.mid(textCursor().selectionEnd(), 1).toStdString()[0];
if (isalnum(prevChar) || isalnum(nextChar))
return;
auto qselection = textCursor().selectedText();
auto selection = qselection.toStdString();
//We also only care about selections that do not themselves contain nonalphanumerical characters
if (std::find_if(selection.begin(), selection.end(), [](char c) { return !isalnum(c); }) != selection.end())
return;
//Prepare text format
QTextCharFormat format;
format.setBackground(Qt::green);
//Find all words in our document that match the selected word and apply the background format to them
size_t pos = 0;
auto reg = QRegExp(qselection);
auto cur = textCursor();
auto index = reg.indexIn(plaintext, pos);
while (index >= 0)
{
//Select matched text and apply format
cur.setPosition(index);
cur.movePosition(QTextCursor::EndOfWord, QTextCursor::KeepAnchor, 1);
cur.mergeCharFormat(format); //This causes the selectChangeHandler function to terminate and then execute again, causing an infinite loop leading to a stack overflow
//Move to next match
pos = index + (size_t)reg.matchedLength();
index = reg.indexIn(plaintext, pos);
}
}
};

我怀疑格式由于某种原因未能应用，可能导致在Qt内部捕获的异常并终止父函数。我试着在有问题的区域周围添加我自己的try-catch处理程序，但它什么也没做(如预期的那样)。

我不确定这是我的错还是Qt内部的错误。有人知道我做错了什么或如何解决这个问题吗?

Answer 1

正在生成一个无限循环，因为似乎获取文本更改也会更改选择。一个可能的解决方案是使用QSignalBlocker阻塞信号:

void selectChangeHandler()
{
const QSignalBlocker blocker(this); // <--- this line
//Ignore empty selections
if (textCursor().selectionStart() >= textCursor().selectionEnd())
return;
// ...