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?

问题描述

我需要将文本附加到 QPlainTextEdit 而不向文本添加换行符，但是 appendPlainText() 和 appendHtml() 两种方法都添加了实际上是新的段落.

I need to append text to QPlainTextEdit without adding a newline to the text, but both methods appendPlainText() and appendHtml() adds actually new paragraph.

我可以用 QTextCursor 手动完成:

I can do that manually with QTextCursor:

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

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

这行得通，但如果在追加之前滚动到底部，我还需要将滚动保持在底部.

That works, but I also need to keep scroll at bottom if it was at bottom before append.

我试图从 Qt 的源代码中复制逻辑，但我坚持下去，因为实际上使用了 QPlainTextEditPrivate 类，并且没有它我找不到做同样事情的方法:比如说，我在 QPlainTextEdit 中没有看到方法 verticalOffset().

I tried to copy logic from Qt's sources, but I stuck on it, because there actually QPlainTextEditPrivate class is used, and I can't find the way to do the same without it: say, I don't see method verticalOffset() in QPlainTextEdit.

实际上，这些来源包含许多奇怪的(至少乍一看)的东西，我不知道如何实现这一点.

Actually, these sources contain many weird (at the first look, at least) things, and I have no idea how to implement this.

这里是append()的源代码:http://code.qt.io/cgit/qt/qt.git/tree/src/gui/widgets/qplaintextedit.cpp#n2763

推荐答案

好吧，我不确定我的解决方案是否真的不错"，但它似乎对我有用:我刚刚创建了一个新类 QPlainTextEdit_My 继承自 QPlainTextEdit，新增方法 appendPlainTextNoNL()、appendHtmlNoNL()、insertNL()>.

Ok, I'm not sure if my solution is actually "nice", but it seems to work for me: I just made new class QPlainTextEdit_My inherited from QPlainTextEdit, and added new methods appendPlainTextNoNL(), appendHtmlNoNL(), insertNL().

请注意:仔细阅读关于参数check_nl和check_br的评论，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.

Please NOTE: read comments about params check_nl and check_br carefully, this is important! I spent several hours to figure out why is my widget so slow when I append text without new paragraphs.

/******************************************************************************************
 * 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 
 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('
');

      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，atBottom 的计算要复杂得多:

I'm confused because in original code there are much more complicated calculations of 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.

But my easy solution seems to work too.

这篇关于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?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！