获取空行的格式

Question

我对 QTextBlock::iterator 的工作原理有点困惑：

文档在普通文本上显示了如何使用它的清晰示例：

QTextBlock::iterator it;
for (it = currentBlock.begin(); !(it.atEnd()); ++it) {
    QTextFragment currentFragment = it.fragment();
    if (currentFragment.isValid())
        processFragment(currentFragment);
}

我在空文本行上遇到问题。在这些方面，

it = currentBlock.begin();
if(it.atEnd())
    // returns true !

我仍然需要能够读取格式（字符和块）

我应该检查最后的块吗？除了新行之外，还有其他方法可以测试块吗？

我目前的解决方案：同时检查最后一个迭代器，与 "for" 循环分开，并测试它是否是文档中的最后一个块（如果我尝试获取最后一个块的片段在文档中，程序崩溃了）。

看来我在违背文档...我应该如何获取空行的格式？

编辑：

我的旧解决方案：

QTextBlock currentBlock = document()->findBlock(selStart);
QTextBlock lastBlock = document()->lastBlock();
while (currentBlock.isValid())
{
    QTextBlock::iterator it = currentBlock.begin();
    if(currentBlock != lastBlock && it.atEnd())
    {
        QTextFragment currentFragment = it.fragment();
        if (currentFragment.isValid())
        {
            QTextCharFormat f = currentFragment.charFormat();
            // do something
        }
    } 
    else
    {
        for (; !(it.atEnd()); ++it)
        {
            QTextFragment currentFragment = it.fragment();
            if (currentFragment.isValid())
            {
                // do stuff
                QTextCharFormat f = currentFragment.charFormat();
                // do stuff
            }
        }
    }
}

基于 Tarod 回答的新解决方案消除了一项测试（但似乎行为不太一致）

QTextBlock currentBlock = document()->findBlock(selStart);
QTextBlock lastBlock = document()->lastBlock();
while (currentBlock.isValid())
{
    QTextBlock::iterator it = currentBlock.begin();
    if(currentBlock != lastBlock && it.atEnd())
    {
        QTextCharFormat f = currentBlock.charFormat();
        // do something
    } 
    else
    {
        for (; !(it.atEnd()); ++it)
        {
            QTextFragment currentFragment = it.fragment();
            if (currentFragment.isValid())
            {
                // do stuff
                QTextCharFormat f = currentFragment.charFormat();
                // do stuff
            }
        }
    }
}

我仍然需要检查最后一个块并避免在空块时使用它，有时它会崩溃。

Answer 1

我认为问题在于您只是遍历 QTextBlock 并阅读其文本片段的内容。在这种情况下，对于一个空 QTextBlock，如您所证明的，currentBlock.begin() == it.atEnd() 因为 QTextBlock 没有任何文本片段。

您应该遍历所有文档文本块，获取所需信息，如果需要，遍历每个文本块以阅读文本片段的序列。

在下面的示例中，#3 块是一个空行 (\n\n)。尽管由于 QTextBlockFormat 和 QTextCharFormat.

我们仍然有关于此文本块的信息，但您不会看到行 qDebug() << "I am a QTextBlock with text!" 打印出来

main.cpp

#include <QApplication>
#include "graphicstextitem_3.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    GraphicsTextItem_3 g3;
    g3.show();

    return a.exec();
}

graphicstextitem_3.h

#ifndef GRAPHICSTEXTITEM_3_H
#define GRAPHICSTEXTITEM_3_H

#include <QMainWindow>

class QGraphicsScene;
class QGraphicsView;
class QGraphicsTextItem;

class GraphicsTextItem_3 : public QMainWindow
{
    Q_OBJECT
public:
    explicit GraphicsTextItem_3(QMainWindow *parent = 0);

private:
     QGraphicsScene *scene;
     QGraphicsView *view;
     QGraphicsTextItem *item;

signals:

public slots:
};

#endif // GRAPHICSTEXTITEM_3_H

graphicstextitem_3.cpp

#include "graphicstextitem_3.h"
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsTextItem>
#include <QTextCursor>
#include <QTextDocument>
#include <QTextBlock>
#include <QDebug>

GraphicsTextItem_3::GraphicsTextItem_3(QMainWindow *parent) : QMainWindow(parent)
{
    scene = new QGraphicsScene(this);
    view = new QGraphicsView(scene);

    item = new QGraphicsTextItem("Block 0\n Block 1\n Block 2\n\n Block 4");
    item->setTextInteractionFlags(Qt::TextEditorInteraction);
    QFont f = item->font();
    f.setPointSize(30);
    item->setFont(f);

    QTextDocument* doc = item->document();

    for (QTextBlock it = doc->begin(); it != doc->end(); it = it.next())
    {
        QTextBlockFormat block_format = it.blockFormat();
        QTextCharFormat char_format = it.charFormat();

        qDebug() << "*** Block number: " << it.blockNumber()
                 << " with text: " << it.text();

        qDebug() << "* Block format info: "
                 << " leftMargin: " << block_format.leftMargin()
                 << " rightMargin: " << block_format.rightMargin()
                 << " topMargin: " << block_format.topMargin()
                 << " bottomMargin: " << block_format.bottomMargin()
                 << " lineHeight: " << block_format.lineHeight();

        qDebug() << "* Char format info: "
                 << " pointSize: " << char_format.font().pointSize()
                 << " fontFamily: " << char_format.font().family();

        QTextBlock::iterator tb_it = it.begin();

        if (tb_it.atEnd())
        {
            qDebug() << "it.begin() == tb_it.atEnd()";
            /* The application crashes if we get the fragment */
            // tb_it.fragment();
        }

        for (tb_it = it.begin(); !(tb_it.atEnd()); ++tb_it) {
            QTextFragment currentFragment = tb_it.fragment();

            if (currentFragment.isValid())
            {
                qDebug() << "I am a QTextBlock with text!"
                         << " Out of here empty QTextBlock!"
                         << " You - shall not - pass!";
            }
        }
    }

    scene->addItem(item);
    view->setFixedSize(640, 480);

    this->setCentralWidget(view);
}

Answer 2

这是伪代码（对我有用）。简而言之，当方法 atEnd() returns TRUE，然后你追加一个新的 line.

QTextEdit * pwTextEdit = whatever your source;
QTextDocument * poDocument = pwTextEdit->document();

QTextBlock oTextBlock = poDocument->begin();
while (oTextBlock.isValid())
{
    QTextBlock::iterator oTextBlockIterator(oTextBlock.begin());
    while (TRUE)
    {
        if (oTextBlockIterator.atEnd())
        {
            // Append your '\n' here
            break;
        }
        QTextFragment oTextFragment = oTextBlockIterator.fragment();
        QString sText = oTextFragment.text();
        // Process the text from sText
        oTextBlockIterator++;
    }
    oTextBlock = oTextBlock.next();
}

获取空行的格式

Getting formatting of empty lines

formatting

qt

qgraphicsitem

qgraphicstextitem