如何在不添加换行符的情况下将文本附加到QPlainTextEdit,并在底部保持滚动？

Question

我需要将文本追加到QPlainTextEdit不添加新行的文本,但是这两种方法appendPlainText(),并appendHtml()实际上增加了新的段落.

我可以手动执行以下操作QTextCursor:

QTextCursor text_cursor = QTextCursor(my_plain_text_edit->document());
text_cursor.movePosition(QTextCursor::End);

text_cursor.insertText("string to append. ");

这是有效的,但如果它在追加之前我还需要保持在底部滚动.

我试图从Qt的源文件副本的逻辑,但我坚持就可以了,因为那里实际上QPlainTextEditPrivate是使用类,我找不到这样做没有它的方法:比如说,我没有看到的方法verticalOffset()在QPlainTextEdit.

实际上,这些来源包含许多奇怪的东西(至少在初看起来),我不知道如何实现它.

以下是源代码append():http://code.qt.io/cgit/qt/qt.git/tree/src/gui/widgets/qplaintextedit.cpp#n2763

Answer 1

我只想引用我在这里找到的内容:

http://www.jcjc-dev.com/2013/03/qt-48-appending-text-to-qtextedit.html

我们只需要将光标移动到QTextEdit中内容的末尾并使用insertPlainText.在我的代码中,它看起来像这样:

myTextEdit->moveCursor (QTextCursor::End);
myTextEdit->insertPlainText (myString);
myTextEdit->moveCursor (QTextCursor::End);

就如此容易.如果您的应用程序需要在附加文本之前将光标保持在原位,您可以使用QTextCursor::position()和QTextCursor::setPosition()方法,或

只需在修改其位置之前复制光标,然后将其[QTextCursor QTextEdit::textCursor()]设置为光标[void QTextEdit::setTextCursor(const QTextCursor & cursor)].

这是一个例子:

QTextCursor prev_cursor = myTextEdit->textCursor();
myTextEdit->moveCursor (QTextCursor::End);
myTextEdit->insertPlainText (myString);
myTextEdit->setTextCursor (&prev_cursor);

Answer 2

目前的答案对我来说不是一个选择.使用以下方法添加没有新行的html要简单得多.

//logs is a QPlainTextEdit object
ui.logs->moveCursor(QTextCursor::End);
ui.logs->textCursor().insertHtml(out);
ui.logs->moveCursor(QTextCursor::End);

Answer 3

好的，我不确定我的解决方案是否真的“不错”，但它似乎对我有用：我只是QPlainTextEdit_My从 继承了新类QPlainTextEdit，并添加了新方法appendPlainTextNoNL(), appendHtmlNoNL(), insertNL()。

请注意：阅读有关参数的评论check_nl并check_br仔细阅读，这很重要！我花了几个小时来弄清楚为什么我的小部件在没有新段落的情况下附加文本时如此缓慢。

/******************************************************************************************
 * INCLUDED FILES
 *****************************************************************************************/

#include "qplaintextedit_my.h"
#include <QScrollBar>
#include <QTextCursor>
#include <QStringList>
#include <QRegExp>


/******************************************************************************************
 * CONSTRUCTOR, DESTRUCTOR
 *****************************************************************************************/

QPlainTextEdit_My::QPlainTextEdit_My(QWidget *parent) :
   QPlainTextEdit(parent)
{

}

QPlainTextEdit_My::QPlainTextEdit_My(const QString &text, QWidget *parent) :
   QPlainTextEdit(text, parent)
{

}        

/******************************************************************************************
 * METHODS
 *****************************************************************************************/

/* private      */

/* protected    */

/* public       */

/**
 * append html without adding new line (new paragraph)
 *
 * @param html       html text to append
 * @param check_nl   if true, then text will be splitted by \n char,
 *                   and each substring will be added as separate QTextBlock.
 *                   NOTE: this important: if you set this to false,
 *                   then you should append new blocks manually (say, by calling appendNL() )
 *                   because one huge block will significantly slow down your widget.
 */
void QPlainTextEdit_My::appendPlainTextNoNL(const QString &text, bool check_nl)
{
   QScrollBar *p_scroll_bar = this->verticalScrollBar();
   bool bool_at_bottom = (p_scroll_bar->value() == p_scroll_bar->maximum());

   if (!check_nl){
      QTextCursor text_cursor = QTextCursor(this->document());
      text_cursor.movePosition(QTextCursor::End);
      text_cursor.insertText(text);
   } else {
      QTextCursor text_cursor = QTextCursor(this->document());
      text_cursor.beginEditBlock();

      text_cursor.movePosition(QTextCursor::End);

      QStringList string_list = text.split('\n');

      for (int i = 0; i < string_list.size(); i++){
         text_cursor.insertText(string_list.at(i));
         if ((i + 1) < string_list.size()){
            text_cursor.insertBlock();
         }
      }


      text_cursor.endEditBlock();
   }

   if (bool_at_bottom){
      p_scroll_bar->setValue(p_scroll_bar->maximum());
   }
}

/**
 * append html without adding new line (new paragraph)
 *
 * @param html       html text to append
 * @param check_br   if true, then text will be splitted by "<br>" tag,
 *                   and each substring will be added as separate QTextBlock.
 *                   NOTE: this important: if you set this to false,
 *                   then you should append new blocks manually (say, by calling appendNL() )
 *                   because one huge block will significantly slow down your widget.
 */
void QPlainTextEdit_My::appendHtmlNoNL(const QString &html, bool check_br)
{
   QScrollBar *p_scroll_bar = this->verticalScrollBar();
   bool bool_at_bottom = (p_scroll_bar->value() == p_scroll_bar->maximum());

   if (!check_br){
      QTextCursor text_cursor = QTextCursor(this->document());
      text_cursor.movePosition(QTextCursor::End);
      text_cursor.insertHtml(html);
   } else {

      QTextCursor text_cursor = QTextCursor(this->document());
      text_cursor.beginEditBlock();

      text_cursor.movePosition(QTextCursor::End);

      QStringList string_list = html.split(QRegExp("\\<br\\s*\\/?\\>", Qt::CaseInsensitive));

      for (int i = 0; i < string_list.size(); i++){
         text_cursor.insertHtml( string_list.at(i) );
         if ((i + 1) < string_list.size()){
            text_cursor.insertBlock();
         }
      }

      text_cursor.endEditBlock();
   }

   if (bool_at_bottom){
      p_scroll_bar->setValue(p_scroll_bar->maximum());
   }
}

/**
 * Just insert new QTextBlock to the text.
 * (in fact, adds new paragraph)
 */
void QPlainTextEdit_My::insertNL()
{
   QScrollBar *p_scroll_bar = this->verticalScrollBar();
   bool bool_at_bottom = (p_scroll_bar->value() == p_scroll_bar->maximum());

   QTextCursor text_cursor = QTextCursor(this->document());
   text_cursor.movePosition(QTextCursor::End);
   text_cursor.insertBlock();

   if (bool_at_bottom){
      p_scroll_bar->setValue(p_scroll_bar->maximum());
   }
}

我很困惑，因为在原始代码中有更复杂的计算atBottom：

const bool atBottom =  q->isVisible()
                       && (control->blockBoundingRect(document->lastBlock()).bottom() - verticalOffset()
                           <= viewport->rect().bottom());

和needScroll：

if (atBottom) {
    const bool needScroll =  !centerOnScroll
                             || control->blockBoundingRect(document->lastBlock()).bottom() - verticalOffset()
                             > viewport->rect().bottom();
    if (needScroll)
        vbar->setValue(vbar->maximum());
}

但我的简单解决方案似乎也有效。