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42 #include "qstatictext.h"
43 #include "qstatictext_p.h"
44 #include <private/qtextengine_p.h>
45 #include <private/qfontengine_p.h>
46 #include <qabstracttextdocumentlayout.h>
52 \brief The QStaticText class enables optimized drawing of text when the text and its layout
60 QStaticText provides a way to cache layout data for a block of text so that it can be drawn
61 more efficiently than by using QPainter::drawText() in which the layout information is
62 recalculated with every call.
64 The class primarily provides an optimization for cases where the text, its font and the
65 transformations on the painter are static over several paint events. If the text or its layout
66 is changed for every iteration, QPainter::drawText() is the more efficient alternative, since
67 the static text's layout would have to be recalculated to take the new state into consideration.
69 Translating the painter will not cause the layout of the text to be recalculated, but will cause
70 a very small performance impact on drawStaticText(). Altering any other parts of the painter's
71 transformation or the painter's font will cause the layout of the static text to be
72 recalculated. This should be avoided as often as possible to maximize the performance
73 benefit of using QStaticText.
75 In addition, only affine transformations are supported by drawStaticText(). Calling
76 drawStaticText() on a projected painter will perform slightly worse than using the regular
77 drawText() call, so this should be avoided.
80 class MyWidget: public QWidget
83 MyWidget(QWidget *parent = 0) : QWidget(parent), m_staticText("This is static text")
86 void paintEvent(QPaintEvent *)
88 QPainter painter(this);
89 painter.drawStaticText(0, 0, m_staticText);
93 QStaticText m_staticText;
97 The QStaticText class can be used to mimic the behavior of QPainter::drawText() to a specific
98 point with no boundaries, and also when QPainter::drawText() is called with a bounding
101 If a bounding rectangle is not required, create a QStaticText object without setting a preferred
102 text width. The text will then occupy a single line.
104 If you set a text width on the QStaticText object, this will bound the text. The text will
105 be formatted so that no line exceeds the given width. The text width set for QStaticText will
106 not automatically be used for clipping. To achieve clipping in addition to line breaks, use
107 QPainter::setClipRect(). The position of the text is decided by the argument passed to
108 QPainter::drawStaticText() and can change from call to call with a minimal impact on
111 For extra convenience, it is possible to apply formatting to the text using the HTML subset
112 supported by QTextDocument. QStaticText will attempt to guess the format of the input text using
113 Qt::mightBeRichText(), and interpret it as rich text if this function returns true. To force
114 QStaticText to display its contents as either plain text or rich text, use the function
115 QStaticText::setTextFormat() and pass in, respectively, Qt::PlainText and Qt::RichText.
117 QStaticText can only represent text, so only HTML tags which alter the layout or appearance of
118 the text will be respected. Adding an image to the input HTML, for instance, will cause the
119 image to be included as part of the layout, affecting the positions of the text glyphs, but it
120 will not be displayed. The result will be an empty area the size of the image in the output.
121 Similarly, using tables will cause the text to be laid out in table format, but the borders
124 If it's the first time the static text is drawn, or if the static text, or the painter's font
125 has been altered since the last time it was drawn, the text's layout has to be
126 recalculated. On some paint engines, changing the matrix of the painter will also cause the
127 layout to be recalculated. In particular, this will happen for any engine except for the
128 OpenGL2 paint engine. Recalculating the layout will impose an overhead on the
129 QPainter::drawStaticText() call where it occurs. To avoid this overhead in the paint event, you
130 can call prepare() ahead of time to ensure that the layout is calculated.
132 \sa QPainter::drawText(), QPainter::drawStaticText(), QTextLayout, QTextDocument
136 \enum QStaticText::PerformanceHint
138 This enum the different performance hints that can be set on the QStaticText. These hints
139 can be used to indicate that the QStaticText should use additional caches, if possible,
140 to improve performance at the expense of memory. In particular, setting the performance hint
141 AggressiveCaching on the QStaticText will improve performance when using the OpenGL graphics
142 system or when drawing to a QOpenGLWidget.
144 \value ModerateCaching Do basic caching for high performance at a low memory cost.
145 \value AggressiveCaching Use additional caching when available. This may improve performance
146 at a higher memory cost.
150 Constructs an empty QStaticText
152 QStaticText::QStaticText()
153 : data(new QStaticTextPrivate)
158 Constructs a QStaticText object with the given \a text.
160 QStaticText::QStaticText(const QString &text)
161 : data(new QStaticTextPrivate)
168 Constructs a QStaticText object which is a copy of \a other.
170 QStaticText::QStaticText(const QStaticText &other)
176 Destroys the QStaticText.
178 QStaticText::~QStaticText()
180 Q_ASSERT(!data || data->ref >= 1);
186 void QStaticText::detach()
193 Prepares the QStaticText object for being painted with the given \a matrix and the given \a font
194 to avoid overhead when the actual drawStaticText() call is made.
196 When drawStaticText() is called, the layout of the QStaticText will be recalculated if any part
197 of the QStaticText object has changed since the last time it was drawn. It will also be
198 recalculated if the painter's font is not the same as when the QStaticText was last drawn, or,
199 on any other paint engine than the OpenGL2 engine, if the painter's matrix has been altered
200 since the static text was last drawn.
202 To avoid the overhead of creating the layout the first time you draw the QStaticText after
203 making changes, you can use the prepare() function and pass in the \a matrix and \a font you
204 expect to use when drawing the text.
206 \sa QPainter::setFont(), QPainter::setMatrix()
208 void QStaticText::prepare(const QTransform &matrix, const QFont &font)
210 data->matrix = matrix;
217 Assigns \a other to this QStaticText.
219 QStaticText &QStaticText::operator=(const QStaticText &other)
226 Compares \a other to this QStaticText. Returns true if the texts, fonts and text widths
229 bool QStaticText::operator==(const QStaticText &other) const
231 return (data == other.data
232 || (data->text == other.data->text
233 && data->font == other.data->font
234 && data->textWidth == other.data->textWidth));
238 Compares \a other to this QStaticText. Returns true if the texts, fonts or maximum sizes
241 bool QStaticText::operator!=(const QStaticText &other) const
243 return !(*this == other);
247 Sets the text of the QStaticText to \a text.
249 \note This function will cause the layout of the text to require recalculation.
253 void QStaticText::setText(const QString &text)
261 Sets the text format of the QStaticText to \a textFormat. If \a textFormat is set to
262 Qt::AutoText (the default), the format of the text will try to be determined using the
263 function Qt::mightBeRichText(). If the text format is Qt::PlainText, then the text will be
264 displayed as is, whereas it will be interpreted as HTML if the format is Qt::RichText. HTML tags
265 that alter the font of the text, its color, or its layout are supported by QStaticText.
267 \note This function will cause the layout of the text to require recalculation.
269 \sa textFormat(), setText(), text()
271 void QStaticText::setTextFormat(Qt::TextFormat textFormat)
274 data->textFormat = textFormat;
279 Returns the text format of the QStaticText.
281 \sa setTextFormat(), setText(), text()
283 Qt::TextFormat QStaticText::textFormat() const
285 return Qt::TextFormat(data->textFormat);
289 Returns the text of the QStaticText.
293 QString QStaticText::text() const
299 Sets the performance hint of the QStaticText according to the \a
300 performanceHint provided. The \a performanceHint is used to
301 customize how much caching is done internally to improve
304 The default is QStaticText::ModerateCaching.
306 \note This function will cause the layout of the text to require recalculation.
308 \sa performanceHint()
310 void QStaticText::setPerformanceHint(PerformanceHint performanceHint)
312 if ((performanceHint == ModerateCaching && !data->useBackendOptimizations)
313 || (performanceHint == AggressiveCaching && data->useBackendOptimizations)) {
317 data->useBackendOptimizations = (performanceHint == AggressiveCaching);
322 Returns which performance hint is set for the QStaticText.
324 \sa setPerformanceHint()
326 QStaticText::PerformanceHint QStaticText::performanceHint() const
328 return data->useBackendOptimizations ? AggressiveCaching : ModerateCaching;
332 Sets the text option structure that controls the layout process to the given \a textOption.
336 void QStaticText::setTextOption(const QTextOption &textOption)
339 data->textOption = textOption;
344 Returns the current text option used to control the layout process.
346 QTextOption QStaticText::textOption() const
348 return data->textOption;
352 Sets the preferred width for this QStaticText. If the text is wider than the specified width,
353 it will be broken into multiple lines and grow vertically. If the text cannot be split into
354 multiple lines, it will be larger than the specified \a textWidth.
356 Setting the preferred text width to a negative number will cause the text to be unbounded.
358 Use size() to get the actual size of the text.
360 \note This function will cause the layout of the text to require recalculation.
362 \sa textWidth(), size()
364 void QStaticText::setTextWidth(qreal textWidth)
367 data->textWidth = textWidth;
372 Returns the preferred width for this QStaticText.
376 qreal QStaticText::textWidth() const
378 return data->textWidth;
382 Returns the size of the bounding rect for this QStaticText.
386 QSizeF QStaticText::size() const
388 if (data->needsRelayout)
390 return data->actualSize;
393 QStaticTextPrivate::QStaticTextPrivate()
394 : textWidth(-1.0), items(0), itemCount(0), glyphPool(0), positionPool(0), charPool(0),
395 needsRelayout(true), useBackendOptimizations(false), textFormat(Qt::AutoText),
396 untransformedCoordinates(false)
400 QStaticTextPrivate::QStaticTextPrivate(const QStaticTextPrivate &other)
401 : text(other.text), font(other.font), textWidth(other.textWidth), matrix(other.matrix),
402 items(0), itemCount(0), glyphPool(0), positionPool(0), charPool(0), textOption(other.textOption),
403 needsRelayout(true), useBackendOptimizations(other.useBackendOptimizations),
404 textFormat(other.textFormat), untransformedCoordinates(other.untransformedCoordinates)
408 QStaticTextPrivate::~QStaticTextPrivate()
412 delete[] positionPool;
416 QStaticTextPrivate *QStaticTextPrivate::get(const QStaticText *q)
418 return q->data.data();
423 class DrawTextItemRecorder: public QPaintEngine
426 DrawTextItemRecorder(bool untransformedCoordinates, bool useBackendOptimizations)
427 : m_dirtyPen(false), m_useBackendOptimizations(useBackendOptimizations),
428 m_untransformedCoordinates(untransformedCoordinates), m_currentColor(Qt::black)
432 virtual void updateState(const QPaintEngineState &newState)
434 if (newState.state() & QPaintEngine::DirtyPen
435 && newState.pen().color() != m_currentColor) {
437 m_currentColor = newState.pen().color();
441 virtual void drawTextItem(const QPointF &position, const QTextItem &textItem)
443 const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);
445 QStaticTextItem currentItem;
446 currentItem.setFontEngine(ti.fontEngine);
447 currentItem.font = ti.font();
448 currentItem.charOffset = m_chars.size();
449 currentItem.numChars = ti.num_chars;
450 currentItem.glyphOffset = m_glyphs.size(); // Store offset into glyph pool
451 currentItem.positionOffset = m_glyphs.size(); // Offset into position pool
452 currentItem.useBackendOptimizations = m_useBackendOptimizations;
454 currentItem.color = m_currentColor;
456 QTransform matrix = m_untransformedCoordinates ? QTransform() : state->transform();
457 matrix.translate(position.x(), position.y());
459 QVarLengthArray<glyph_t> glyphs;
460 QVarLengthArray<QFixedPoint> positions;
461 ti.fontEngine->getGlyphPositions(ti.glyphs, matrix, ti.flags, glyphs, positions);
463 int size = glyphs.size();
464 Q_ASSERT(size == positions.size());
465 currentItem.numGlyphs = size;
467 m_glyphs.resize(m_glyphs.size() + size);
468 m_positions.resize(m_glyphs.size());
469 m_chars.resize(m_chars.size() + ti.num_chars);
471 glyph_t *glyphsDestination = m_glyphs.data() + currentItem.glyphOffset;
472 memcpy(glyphsDestination, glyphs.constData(), sizeof(glyph_t) * currentItem.numGlyphs);
474 QFixedPoint *positionsDestination = m_positions.data() + currentItem.positionOffset;
475 memcpy(positionsDestination, positions.constData(), sizeof(QFixedPoint) * currentItem.numGlyphs);
477 QChar *charsDestination = m_chars.data() + currentItem.charOffset;
478 memcpy(charsDestination, ti.chars, sizeof(QChar) * currentItem.numChars);
480 m_items.append(currentItem);
483 virtual void drawPolygon(const QPointF *, int , PolygonDrawMode )
485 /* intentionally empty */
488 virtual bool begin(QPaintDevice *) { return true; }
489 virtual bool end() { return true; }
490 virtual void drawPixmap(const QRectF &, const QPixmap &, const QRectF &) {}
491 virtual Type type() const
496 QVector<QStaticTextItem> items() const
501 QVector<QFixedPoint> positions() const
506 QVector<glyph_t> glyphs() const
511 QVector<QChar> chars() const
517 QVector<QStaticTextItem> m_items;
518 QVector<QFixedPoint> m_positions;
519 QVector<glyph_t> m_glyphs;
520 QVector<QChar> m_chars;
523 bool m_useBackendOptimizations;
524 bool m_untransformedCoordinates;
525 QColor m_currentColor;
528 class DrawTextItemDevice: public QPaintDevice
531 DrawTextItemDevice(bool untransformedCoordinates, bool useBackendOptimizations)
533 m_paintEngine = new DrawTextItemRecorder(untransformedCoordinates,
534 useBackendOptimizations);
537 ~DrawTextItemDevice()
539 delete m_paintEngine;
542 int metric(PaintDeviceMetric m) const
553 case PdmPhysicalDpiX:
554 val = qt_defaultDpiX();
557 case PdmPhysicalDpiY:
558 val = qt_defaultDpiY();
568 qWarning("DrawTextItemDevice::metric: Invalid metric command");
573 virtual QPaintEngine *paintEngine() const
575 return m_paintEngine;
578 QVector<glyph_t> glyphs() const
580 return m_paintEngine->glyphs();
583 QVector<QFixedPoint> positions() const
585 return m_paintEngine->positions();
588 QVector<QStaticTextItem> items() const
590 return m_paintEngine->items();
593 QVector<QChar> chars() const
595 return m_paintEngine->chars();
599 DrawTextItemRecorder *m_paintEngine;
603 void QStaticTextPrivate::paintText(const QPointF &topLeftPosition, QPainter *p)
605 bool preferRichText = textFormat == Qt::RichText
606 || (textFormat == Qt::AutoText && Qt::mightBeRichText(text));
608 if (!preferRichText) {
609 QTextLayout textLayout;
610 textLayout.setText(text);
611 textLayout.setFont(font);
612 textLayout.setTextOption(textOption);
614 qreal leading = QFontMetricsF(font).leading();
615 qreal height = -leading;
617 textLayout.beginLayout();
619 QTextLine line = textLayout.createLine();
623 if (textWidth >= 0.0)
624 line.setLineWidth(textWidth);
626 line.setPosition(QPointF(0.0, height));
627 height += line.height();
629 textLayout.endLayout();
631 actualSize = textLayout.boundingRect().size();
632 textLayout.draw(p, topLeftPosition);
634 QTextDocument document;
635 #ifndef QT_NO_CSSPARSER
636 QColor color = p->pen().color();
637 document.setDefaultStyleSheet(QString::fromLatin1("body { color: #%1%2%3 }")
638 .arg(QString::number(color.red(), 16), 2, QLatin1Char('0'))
639 .arg(QString::number(color.green(), 16), 2, QLatin1Char('0'))
640 .arg(QString::number(color.blue(), 16), 2, QLatin1Char('0')));
642 document.setDefaultFont(font);
643 document.setDocumentMargin(0.0);
644 #ifndef QT_NO_TEXTHTMLPARSER
645 document.setHtml(text);
647 document.setPlainText(text);
649 if (textWidth >= 0.0)
650 document.setTextWidth(textWidth);
652 document.adjustSize();
653 document.setDefaultTextOption(textOption);
656 p->translate(topLeftPosition);
657 QAbstractTextDocumentLayout::PaintContext ctx;
658 ctx.palette.setColor(QPalette::Text, p->pen().color());
659 document.documentLayout()->draw(p, ctx);
662 if (textWidth >= 0.0)
663 document.adjustSize(); // Find optimal size
665 actualSize = document.size();
669 void QStaticTextPrivate::init()
673 delete[] positionPool;
676 position = QPointF(0, 0);
678 DrawTextItemDevice device(untransformedCoordinates, useBackendOptimizations);
680 QPainter painter(&device);
681 painter.setFont(font);
682 painter.setTransform(matrix);
684 paintText(QPointF(0, 0), &painter);
687 QVector<QStaticTextItem> deviceItems = device.items();
688 QVector<QFixedPoint> positions = device.positions();
689 QVector<glyph_t> glyphs = device.glyphs();
690 QVector<QChar> chars = device.chars();
692 itemCount = deviceItems.size();
693 items = new QStaticTextItem[itemCount];
695 glyphPool = new glyph_t[glyphs.size()];
696 memcpy(glyphPool, glyphs.constData(), glyphs.size() * sizeof(glyph_t));
698 positionPool = new QFixedPoint[positions.size()];
699 memcpy(positionPool, positions.constData(), positions.size() * sizeof(QFixedPoint));
701 charPool = new QChar[chars.size()];
702 memcpy(charPool, chars.constData(), chars.size() * sizeof(QChar));
704 for (int i=0; i<itemCount; ++i) {
705 items[i] = deviceItems.at(i);
707 items[i].glyphs = glyphPool + items[i].glyphOffset;
708 items[i].glyphPositions = positionPool + items[i].positionOffset;
709 items[i].chars = charPool + items[i].charOffset;
712 needsRelayout = false;
715 QStaticTextItem::~QStaticTextItem()
717 if (m_userData != 0 && !m_userData->ref.deref())
719 m_fontEngine->ref.deref();
722 void QStaticTextItem::setFontEngine(QFontEngine *fe)
724 if (m_fontEngine != 0)
725 m_fontEngine->ref.deref();
727 if (m_fontEngine != 0)
728 m_fontEngine->ref.ref();