如何仅在某些情况下有选择地发出 QTextTexid::textChanged 信号？

Question

能否仅在某些情况下触发 textChanged 信号？例如触发插入文本，插入 space 个字符但不返回 space?

我运行每次文本更改时都会检查 QTextEdit 中的键入字符，并根据结果突出显示背景中只读 QTextEdit 中的文本，用作永远在线的占位符文本用户在打字时查看。如果用户犯了错误，角色会以红色突出显示，并在错误修复后重置为初始背景颜色。按下后退 space 键时会出现问题，因为它被记录为错误，因此前一个字符也突出显示为红色。

 void Widget::onTextChanged()
 {
     QChar c;

     QString txt_contents = txtedit_->toPlainText();

     if(txt_contents.isEmpty()){
         c = '[=11=]';

         //reset text display
         txtdisplay_->clear();
         txtdisplay_->append(*label_text_);
     }
     else
         c = txtedit_->toPlainText().back();
  
     if(!texteditq_->isEmpty()){
         if(c == texteditq_->head()){
             //refresh text display
             correct_++;
             txtdisplay_->clear();
             txtdisplay_->append(*label_text_);

             //remove character that was used for the successful check from the
             //queue
             texteditq_->dequeue();
         }else{
             //set backgroud color to red for errors
             fmt_->setBackground(Qt::red);

             if(!txtedit_->toPlainText().isEmpty()){
                 //move cursor to the end of the editor, where the error is and save
                 //the position the error occurs at
                 c_edit_->movePosition(QTextCursor::End);
                 quint32 error_pos = c_edit_->position();

                 //move the cursor in the display for the background text and
                 //use the KeepAnchor move mode to highlight the misspelled char
                 c_display_->setPosition(error_pos-1,QTextCursor::MoveAnchor);
                 c_display_->setPosition(error_pos,QTextCursor::KeepAnchor);

                 //apply formating to that character
                 c_display_->setCharFormat(*fmt_);
             }
         }
     }
 }

Answer 1

根据 OP 的要求，我发布了一个名为 CustomTextEdit 的 class 解决方案，它是 subclassing QTextEdit。它挂接到 keyPressEvent() 并检查按下的键。如果它不是退格键，那么自定义信号 keyPressed() 将被发射。

class CustomTextEdit : public QTextEdit {
  Q_OBJECT
 public:
  explicit CustomTextEdit(QWidget *parent = nullptr) : QTextEdit(parent) {}

 signals:
  void keyPressed();

 protected:
  void keyPressEvent(QKeyEvent *e) override {
    if (e->key() != Qt::Key_Backspace) {
      emit keyPressed();
    }

    QTextEdit::keyPressEvent(e);
  }
};

如何仅在某些情况下有选择地发出 QTextTexid::textChanged 信号？

How to emit QTextTexid::textChanged signal only in certain cases selectively?

c++

qt

qwidget

qtextedit

textchanged