自已实现 QTextDocument 的绘制

虽然 Qt  中的 QTextDocument  很强大。。但是有时我们还是需要把文档中的内容，绘制到别的地方。。。

 

这时就需要进行文档的绘制了 。。。

 

那么大致的方法是这样的。。

 

 

// myTextDraw.h #pragma once #include "stdafx.h" // 绘制QTextDocument中的指定区域 void drawDocument(QPainter* painter, const QTextDocument* doc, const QRectF& r, const QBrush& brush = Qt::NoBrush/*brush to draw all content.used for shadow draw*/); // 绘制Block及其内容 void drawTextLayout(QPainter* painter, const QTextBlock& block, const QSizeF& sizeToFill, const QBrush& brush); // 绘制文本及其内外边 void drawText(QPainter* painter, QPointF& p, QString& text, const QTextCharFormat& fmt, const QBrush& brush); qreal alignPos(Qt::Alignment a, const qreal& width, const qreal& textWidth); bool needDrawText(const QTextCharFormat& chf); void clearLetterSpacing(QTextDocument* doc, int* blockNum = NULL); void adjustAlignJustify(QTextDocument* doc, qreal DocWidth, int* blockNum = NULL);

 

// myTextDraw.cpp #include "myTextDraw.h" // 第一步 绘制 Document void drawDocument(QPainter* painter, const QTextDocument* doc, const QRectF& r, const QBrush& brush) { if(doc->isEmpty()) return; painter->save(); // 按区域绘制 if (r.isValid()) painter->setClipRect(r, Qt::IntersectClip); QSizeF size = doc->size(); QTextFrameFormat fmt = doc->rootFrame()->frameFormat(); size.setWidth(size.width() - fmt.leftMargin() - fmt.rightMargin()); for (QTextBlock bl = doc->begin(); bl != doc->end(); bl = bl.next()) { // 因为每个QTextDocument 中包含一个QTextLayout drawTextLayout(painter, bl, size , brush); } painter->restore(); } //第二步 绘制 Layout void drawTextLayout(QPainter* painter, const QTextBlock& block, const QSizeF& sizeToFill, const QBrush& brush) { if (!block.isValid()) return; QTextLayout* layout = block.layout(); if(!layout) return; if (layout->lineCount() < 1) return; // 基线，每绘制一行则Y下移一行的位置，X不变 QPointF baseLine = layout->position(); baseLine.setY(baseLine.y() + layout->lineAt(0).ascent()); // 输出位置，以基线Pos为基础，往右移动，每次换行，重置X位置 QPointF outPos = baseLine; // QTextLayout 下一级是 QTextBlock.. // QTextBlock 的下一级又是QTextFragment.. QTextBlock::iterator it; for (it = block.begin(); !(it.atEnd()); ++it) { QTextFragment fragment = it.fragment(); if (!fragment.isValid()) continue; // 获取文本 QString text = fragment.text(); if (text.isEmpty()) continue; // 获取文本格式 QTextCharFormat chf = fragment.charFormat(); int lineNoBegin = layout->lineForTextPosition(fragment.position() - block.position()).lineNumber(); int lineNoEnd = layout->lineForTextPosition(fragment.position() + fragment.length() - 1 - block.position()).lineNumber(); int j = fragment.position(); for (int i = lineNoBegin; i <= lineNoEnd; i++) { QTextLine line = layout->lineAt(i); // 计算输出位置X qreal offset = alignPos(layout->textOption().alignment(), sizeToFill.width(), line.naturalTextWidth()); outPos.setX(outPos.x() + offset); outPos.setY(baseLine.y()); // 获取属于本行的文本 QString textOnLine; while(j < fragment.position() + fragment.length()) { int c = block.position(); int d = line.textStart() + line.textLength(); if (j < c + d) textOnLine.append(text[j - fragment.position()]); else break; j++; } // 绘制属于本行的Fragment中的文本 drawText(painter, outPos, textOnLine, chf, brush); // 有换行的话，要更新BaseLine的Y及outPos的X if(i < lineNoEnd) { // 更新基线位置Y baseLine.setY(baseLine.y() + line.height()); outPos.setX(baseLine.x()); } } } } // 第三步 绘制文字 void drawText(QPainter* painter, QPointF& p, QString& text, const QTextCharFormat& fmt, const QBrush& brush) { painter->setRenderHint(QPainter::Antialiasing, true); painter->setRenderHint(QPainter::TextAntialiasing, true); QFont f = fmt.font(); f.resolve(QFont::AllPropertiesResolved); // 获得第个文字的大小。。 QFontMetricsF fm(f); QRectF textBoundingRect = fm.boundingRect(text); // draw text if(needDrawText(fmt) || brush.style() != Qt::NoBrush) { painter->setFont(f); QPen pen; if(brush.style() == Qt::NoBrush) { QBrush t = fmt.foreground(); if (t.style() == Qt::NoBrush) pen.setBrush(QBrush(QColor(255,255,255))); else if(t.style() != Qt::SolidPattern) pen = QPen(t,0); else { QColor c = t.color(); QColor cc = c.toRgb(); pen.setBrush(QBrush(cc)); } } else { if (brush.style() != Qt::SolidPattern) pen = QPen(brush, 0); else { pen.setBrush(brush); } } painter->setPen(pen); // draw text. painter->drawText(p, text); } p += QPointF(textBoundingRect.width(), 0); } qreal alignPos(Qt::Alignment a, const qreal& width, const qreal& textWidth) { if(a & Qt::AlignRight) return width - textWidth; else if(!(a & Qt::AlignLeft)) return (width - textWidth) / 2; return 0; } bool needDrawText(const QTextCharFormat& chf) { return true; } void clearLetterSpacing(QTextDocument* doc, int* blockNum) { bool bAllBlock = !blockNum ? true : false; QVector<QTextBlock> blocks; if (bAllBlock) { for(QTextBlock block = doc->begin(); block != doc->end(); block = block.next()) blocks.push_back(block); } else { blocks.push_back(doc->findBlockByNumber(*blockNum)); } // 清空所有文字的字间距 for(int idx = 0; idx < blocks.size(); idx++) { QTextCursor cursor(blocks[idx]); for (int i = 0; i < blocks[idx].layout()->lineCount(); i++) { cursor.select(QTextCursor::LineUnderCursor); QTextCharFormat fmt; fmt.setFontLetterSpacing(100); cursor.mergeCharFormat(fmt); cursor.movePosition(QTextCursor::Down); } } } // 将QTextDocument中的指定Block置为发散对其方式，DocWidth为限定宽度,注意本函数会破坏原有的字符间距 void adjustAlignJustify(QTextDocument* doc, qreal DocWidth, int* blockNum) { // 清空文字的字间距 clearLetterSpacing(doc, blockNum); // 获取要发散对其的Block bool bAllBlock = !blockNum ? true : false; QVector<QTextBlock> blocks; if (bAllBlock) { for(QTextBlock block = doc->begin(); block != doc->end(); block = block.next()) blocks.push_back(block); } else { blocks.push_back(doc->findBlockByNumber(*blockNum)); } // 获取Layout的Margin QTextFrameFormat frame = doc->rootFrame()->frameFormat(); // 发散对齐,计算字间距 for(int idx = 0; idx < blocks.size(); idx++) { QTextCursor cursor(blocks[idx]); for (int i = 0; i < blocks[idx].layout()->lineCount(); i++) { QTextLine line = blocks[idx].layout()->lineAt(i); // 计算最后一个字的宽度 cursor.setPosition(blocks[idx].position() + line.textStart() + line.textLength() - 1); cursor.setPosition(cursor.position() + 1, QTextCursor::KeepAnchor); QString text = cursor.selectedText(); if (text.isEmpty()) { cursor.movePosition(QTextCursor::Down); continue; } QFontMetricsF m(cursor.charFormat().font()); qreal lastCharWidth = m.width(text[0]); // 计算字符间距 qreal widthOfLayout = DocWidth - (frame.leftMargin() + frame.rightMargin()) - lastCharWidth; qreal widthOfText = line.naturalTextRect().width() - lastCharWidth; qreal percentOfSpacing = widthOfLayout / widthOfText * 100; if (percentOfSpacing > 100.0f) { // 选择第一个字到最后一个字的前一个字，设置这些字的字间距 cursor.setPosition(blocks[idx].position()); int pos = blocks[idx].position() + line.textStart() + line.textLength() - 1; cursor.setPosition(pos, QTextCursor::KeepAnchor); QTextCharFormat fmt; fmt.setFontLetterSpacing(percentOfSpacing); cursor.mergeCharFormat(fmt); } cursor.movePosition(QTextCursor::Down); } } }