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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
62 QStaticText provides a way to cache layout data for a block of text so that it can be drawn
63 more efficiently than by using QPainter::drawText() in which the layout information is
64 recalculated with every call.
66 The class primarily provides an optimization for cases where the text, its font and the
67 transformations on the painter are static over several paint events. If the text or its layout
68 is changed for every iteration, QPainter::drawText() is the more efficient alternative, since
69 the static text's layout would have to be recalculated to take the new state into consideration.
71 Translating the painter will not cause the layout of the text to be recalculated, but will cause
72 a very small performance impact on drawStaticText(). Altering any other parts of the painter's
73 transformation or the painter's font will cause the layout of the static text to be
74 recalculated. This should be avoided as often as possible to maximize the performance
75 benefit of using QStaticText.
77 In addition, only affine transformations are supported by drawStaticText(). Calling
78 drawStaticText() on a projected painter will perform slightly worse than using the regular
79 drawText() call, so this should be avoided.
82 class MyWidget: public QWidget
85 MyWidget(QWidget *parent = 0) : QWidget(parent), m_staticText("This is static text")
88 void paintEvent(QPaintEvent *)
90 QPainter painter(this);
91 painter.drawStaticText(0, 0, m_staticText);
95 QStaticText m_staticText;
99 The QStaticText class can be used to mimic the behavior of QPainter::drawText() to a specific
100 point with no boundaries, and also when QPainter::drawText() is called with a bounding
103 If a bounding rectangle is not required, create a QStaticText object without setting a preferred
104 text width. The text will then occupy a single line.
106 If you set a text width on the QStaticText object, this will bound the text. The text will
107 be formatted so that no line exceeds the given width. The text width set for QStaticText will
108 not automatically be used for clipping. To achieve clipping in addition to line breaks, use
109 QPainter::setClipRect(). The position of the text is decided by the argument passed to
110 QPainter::drawStaticText() and can change from call to call with a minimal impact on
113 For extra convenience, it is possible to apply formatting to the text using the HTML subset
114 supported by QTextDocument. QStaticText will attempt to guess the format of the input text using
115 Qt::mightBeRichText(), and interpret it as rich text if this function returns true. To force
116 QStaticText to display its contents as either plain text or rich text, use the function
117 QStaticText::setTextFormat() and pass in, respectively, Qt::PlainText and Qt::RichText.
119 QStaticText can only represent text, so only HTML tags which alter the layout or appearance of
120 the text will be respected. Adding an image to the input HTML, for instance, will cause the
121 image to be included as part of the layout, affecting the positions of the text glyphs, but it
122 will not be displayed. The result will be an empty area the size of the image in the output.
123 Similarly, using tables will cause the text to be laid out in table format, but the borders
126 If it's the first time the static text is drawn, or if the static text, or the painter's font
127 has been altered since the last time it was drawn, the text's layout has to be
128 recalculated. On some paint engines, changing the matrix of the painter will also cause the
129 layout to be recalculated. In particular, this will happen for any engine except for the
130 OpenGL2 paint engine. Recalculating the layout will impose an overhead on the
131 QPainter::drawStaticText() call where it occurs. To avoid this overhead in the paint event, you
132 can call prepare() ahead of time to ensure that the layout is calculated.
134 \sa QPainter::drawText(), QPainter::drawStaticText(), QTextLayout, QTextDocument
138 \enum QStaticText::PerformanceHint
140 This enum the different performance hints that can be set on the QStaticText. These hints
141 can be used to indicate that the QStaticText should use additional caches, if possible,
142 to improve performance at the expense of memory. In particular, setting the performance hint
143 AggressiveCaching on the QStaticText will improve performance when using the OpenGL graphics
144 system or when drawing to a QOpenGLWidget.
146 \value ModerateCaching Do basic caching for high performance at a low memory cost.
147 \value AggressiveCaching Use additional caching when available. This may improve performance
148 at a higher memory cost.
152 Constructs an empty QStaticText
154 QStaticText::QStaticText()
155 : data(new QStaticTextPrivate)
160 Constructs a QStaticText object with the given \a text.
162 QStaticText::QStaticText(const QString &text)
163 : data(new QStaticTextPrivate)
170 Constructs a QStaticText object which is a copy of \a other.
172 QStaticText::QStaticText(const QStaticText &other)
178 Destroys the QStaticText.
180 QStaticText::~QStaticText()
182 Q_ASSERT(!data || data->ref.load() >= 1);
188 void QStaticText::detach()
190 if (data->ref.load() != 1)
195 Prepares the QStaticText object for being painted with the given \a matrix and the given \a font
196 to avoid overhead when the actual drawStaticText() call is made.
198 When drawStaticText() is called, the layout of the QStaticText will be recalculated if any part
199 of the QStaticText object has changed since the last time it was drawn. It will also be
200 recalculated if the painter's font is not the same as when the QStaticText was last drawn, or,
201 on any other paint engine than the OpenGL2 engine, if the painter's matrix has been altered
202 since the static text was last drawn.
204 To avoid the overhead of creating the layout the first time you draw the QStaticText after
205 making changes, you can use the prepare() function and pass in the \a matrix and \a font you
206 expect to use when drawing the text.
208 \sa QPainter::setFont(), QPainter::setMatrix()
210 void QStaticText::prepare(const QTransform &matrix, const QFont &font)
212 data->matrix = matrix;
219 Assigns \a other to this QStaticText.
221 QStaticText &QStaticText::operator=(const QStaticText &other)
228 \fn void QStaticText::swap(QStaticText &other)
231 Swaps this static text instance with \a other. This function is
232 very fast and never fails.
236 Compares \a other to this QStaticText. Returns true if the texts, fonts and text widths
239 bool QStaticText::operator==(const QStaticText &other) const
241 return (data == other.data
242 || (data->text == other.data->text
243 && data->font == other.data->font
244 && data->textWidth == other.data->textWidth));
248 Compares \a other to this QStaticText. Returns true if the texts, fonts or maximum sizes
251 bool QStaticText::operator!=(const QStaticText &other) const
253 return !(*this == other);
257 Sets the text of the QStaticText to \a text.
259 \note This function will cause the layout of the text to require recalculation.
263 void QStaticText::setText(const QString &text)
271 Sets the text format of the QStaticText to \a textFormat. If \a textFormat is set to
272 Qt::AutoText (the default), the format of the text will try to be determined using the
273 function Qt::mightBeRichText(). If the text format is Qt::PlainText, then the text will be
274 displayed as is, whereas it will be interpreted as HTML if the format is Qt::RichText. HTML tags
275 that alter the font of the text, its color, or its layout are supported by QStaticText.
277 \note This function will cause the layout of the text to require recalculation.
279 \sa textFormat(), setText(), text()
281 void QStaticText::setTextFormat(Qt::TextFormat textFormat)
284 data->textFormat = textFormat;
289 Returns the text format of the QStaticText.
291 \sa setTextFormat(), setText(), text()
293 Qt::TextFormat QStaticText::textFormat() const
295 return Qt::TextFormat(data->textFormat);
299 Returns the text of the QStaticText.
303 QString QStaticText::text() const
309 Sets the performance hint of the QStaticText according to the \a
310 performanceHint provided. The \a performanceHint is used to
311 customize how much caching is done internally to improve
314 The default is QStaticText::ModerateCaching.
316 \note This function will cause the layout of the text to require recalculation.
318 \sa performanceHint()
320 void QStaticText::setPerformanceHint(PerformanceHint performanceHint)
322 if ((performanceHint == ModerateCaching && !data->useBackendOptimizations)
323 || (performanceHint == AggressiveCaching && data->useBackendOptimizations)) {
327 data->useBackendOptimizations = (performanceHint == AggressiveCaching);
332 Returns which performance hint is set for the QStaticText.
334 \sa setPerformanceHint()
336 QStaticText::PerformanceHint QStaticText::performanceHint() const
338 return data->useBackendOptimizations ? AggressiveCaching : ModerateCaching;
342 Sets the text option structure that controls the layout process to the given \a textOption.
346 void QStaticText::setTextOption(const QTextOption &textOption)
349 data->textOption = textOption;
354 Returns the current text option used to control the layout process.
356 QTextOption QStaticText::textOption() const
358 return data->textOption;
362 Sets the preferred width for this QStaticText. If the text is wider than the specified width,
363 it will be broken into multiple lines and grow vertically. If the text cannot be split into
364 multiple lines, it will be larger than the specified \a textWidth.
366 Setting the preferred text width to a negative number will cause the text to be unbounded.
368 Use size() to get the actual size of the text.
370 \note This function will cause the layout of the text to require recalculation.
372 \sa textWidth(), size()
374 void QStaticText::setTextWidth(qreal textWidth)
377 data->textWidth = textWidth;
382 Returns the preferred width for this QStaticText.
386 qreal QStaticText::textWidth() const
388 return data->textWidth;
392 Returns the size of the bounding rect for this QStaticText.
396 QSizeF QStaticText::size() const
398 if (data->needsRelayout)
400 return data->actualSize;
403 QStaticTextPrivate::QStaticTextPrivate()
404 : textWidth(-1.0), items(0), itemCount(0), glyphPool(0), positionPool(0), charPool(0),
405 needsRelayout(true), useBackendOptimizations(false), textFormat(Qt::AutoText),
406 untransformedCoordinates(false)
410 QStaticTextPrivate::QStaticTextPrivate(const QStaticTextPrivate &other)
411 : text(other.text), font(other.font), textWidth(other.textWidth), matrix(other.matrix),
412 items(0), itemCount(0), glyphPool(0), positionPool(0), charPool(0), textOption(other.textOption),
413 needsRelayout(true), useBackendOptimizations(other.useBackendOptimizations),
414 textFormat(other.textFormat), untransformedCoordinates(other.untransformedCoordinates)
418 QStaticTextPrivate::~QStaticTextPrivate()
422 delete[] positionPool;
426 QStaticTextPrivate *QStaticTextPrivate::get(const QStaticText *q)
428 return q->data.data();
433 class DrawTextItemRecorder: public QPaintEngine
436 DrawTextItemRecorder(bool untransformedCoordinates, bool useBackendOptimizations)
437 : m_dirtyPen(false), m_useBackendOptimizations(useBackendOptimizations),
438 m_untransformedCoordinates(untransformedCoordinates), m_currentColor(Qt::black)
442 virtual void updateState(const QPaintEngineState &newState)
444 if (newState.state() & QPaintEngine::DirtyPen
445 && newState.pen().color() != m_currentColor) {
447 m_currentColor = newState.pen().color();
451 virtual void drawTextItem(const QPointF &position, const QTextItem &textItem)
453 const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);
455 QStaticTextItem currentItem;
456 currentItem.setFontEngine(ti.fontEngine);
457 currentItem.font = ti.font();
458 currentItem.charOffset = m_chars.size();
459 currentItem.numChars = ti.num_chars;
460 currentItem.glyphOffset = m_glyphs.size(); // Store offset into glyph pool
461 currentItem.positionOffset = m_glyphs.size(); // Offset into position pool
462 currentItem.useBackendOptimizations = m_useBackendOptimizations;
464 currentItem.color = m_currentColor;
466 QTransform matrix = m_untransformedCoordinates ? QTransform() : state->transform();
467 matrix.translate(position.x(), position.y());
469 QVarLengthArray<glyph_t> glyphs;
470 QVarLengthArray<QFixedPoint> positions;
471 ti.fontEngine->getGlyphPositions(ti.glyphs, matrix, ti.flags, glyphs, positions);
473 int size = glyphs.size();
474 Q_ASSERT(size == positions.size());
475 currentItem.numGlyphs = size;
477 m_glyphs.resize(m_glyphs.size() + size);
478 m_positions.resize(m_glyphs.size());
479 m_chars.resize(m_chars.size() + ti.num_chars);
481 glyph_t *glyphsDestination = m_glyphs.data() + currentItem.glyphOffset;
482 memcpy(glyphsDestination, glyphs.constData(), sizeof(glyph_t) * currentItem.numGlyphs);
484 QFixedPoint *positionsDestination = m_positions.data() + currentItem.positionOffset;
485 memcpy(positionsDestination, positions.constData(), sizeof(QFixedPoint) * currentItem.numGlyphs);
487 QChar *charsDestination = m_chars.data() + currentItem.charOffset;
488 memcpy(charsDestination, ti.chars, sizeof(QChar) * currentItem.numChars);
490 m_items.append(currentItem);
493 virtual void drawPolygon(const QPointF *, int , PolygonDrawMode )
495 /* intentionally empty */
498 virtual bool begin(QPaintDevice *) { return true; }
499 virtual bool end() { return true; }
500 virtual void drawPixmap(const QRectF &, const QPixmap &, const QRectF &) {}
501 virtual Type type() const
506 QVector<QStaticTextItem> items() const
511 QVector<QFixedPoint> positions() const
516 QVector<glyph_t> glyphs() const
521 QVector<QChar> chars() const
527 QVector<QStaticTextItem> m_items;
528 QVector<QFixedPoint> m_positions;
529 QVector<glyph_t> m_glyphs;
530 QVector<QChar> m_chars;
533 bool m_useBackendOptimizations;
534 bool m_untransformedCoordinates;
535 QColor m_currentColor;
538 class DrawTextItemDevice: public QPaintDevice
541 DrawTextItemDevice(bool untransformedCoordinates, bool useBackendOptimizations)
543 m_paintEngine = new DrawTextItemRecorder(untransformedCoordinates,
544 useBackendOptimizations);
547 ~DrawTextItemDevice()
549 delete m_paintEngine;
552 int metric(PaintDeviceMetric m) const
563 case PdmPhysicalDpiX:
564 val = qt_defaultDpiX();
567 case PdmPhysicalDpiY:
568 val = qt_defaultDpiY();
578 qWarning("DrawTextItemDevice::metric: Invalid metric command");
583 virtual QPaintEngine *paintEngine() const
585 return m_paintEngine;
588 QVector<glyph_t> glyphs() const
590 return m_paintEngine->glyphs();
593 QVector<QFixedPoint> positions() const
595 return m_paintEngine->positions();
598 QVector<QStaticTextItem> items() const
600 return m_paintEngine->items();
603 QVector<QChar> chars() const
605 return m_paintEngine->chars();
609 DrawTextItemRecorder *m_paintEngine;
613 void QStaticTextPrivate::paintText(const QPointF &topLeftPosition, QPainter *p)
615 bool preferRichText = textFormat == Qt::RichText
616 || (textFormat == Qt::AutoText && Qt::mightBeRichText(text));
618 if (!preferRichText) {
619 QTextLayout textLayout;
620 textLayout.setText(text);
621 textLayout.setFont(font);
622 textLayout.setTextOption(textOption);
623 textLayout.setCacheEnabled(true);
625 qreal leading = QFontMetricsF(font).leading();
626 qreal height = -leading;
628 textLayout.beginLayout();
630 QTextLine line = textLayout.createLine();
634 if (textWidth >= 0.0)
635 line.setLineWidth(textWidth);
637 line.setPosition(QPointF(0.0, height));
638 height += line.height();
640 textLayout.endLayout();
642 actualSize = textLayout.boundingRect().size();
643 textLayout.draw(p, topLeftPosition);
645 QTextDocument document;
646 #ifndef QT_NO_CSSPARSER
647 QColor color = p->pen().color();
648 document.setDefaultStyleSheet(QString::fromLatin1("body { color: #%1%2%3 }")
649 .arg(QString::number(color.red(), 16), 2, QLatin1Char('0'))
650 .arg(QString::number(color.green(), 16), 2, QLatin1Char('0'))
651 .arg(QString::number(color.blue(), 16), 2, QLatin1Char('0')));
653 document.setDefaultFont(font);
654 document.setDocumentMargin(0.0);
655 #ifndef QT_NO_TEXTHTMLPARSER
656 document.setHtml(text);
658 document.setPlainText(text);
660 if (textWidth >= 0.0)
661 document.setTextWidth(textWidth);
663 document.adjustSize();
664 document.setDefaultTextOption(textOption);
667 p->translate(topLeftPosition);
668 QAbstractTextDocumentLayout::PaintContext ctx;
669 ctx.palette.setColor(QPalette::Text, p->pen().color());
670 document.documentLayout()->draw(p, ctx);
673 if (textWidth >= 0.0)
674 document.adjustSize(); // Find optimal size
676 actualSize = document.size();
680 void QStaticTextPrivate::init()
684 delete[] positionPool;
687 position = QPointF(0, 0);
689 DrawTextItemDevice device(untransformedCoordinates, useBackendOptimizations);
691 QPainter painter(&device);
692 painter.setFont(font);
693 painter.setTransform(matrix);
695 paintText(QPointF(0, 0), &painter);
698 QVector<QStaticTextItem> deviceItems = device.items();
699 QVector<QFixedPoint> positions = device.positions();
700 QVector<glyph_t> glyphs = device.glyphs();
701 QVector<QChar> chars = device.chars();
703 itemCount = deviceItems.size();
704 items = new QStaticTextItem[itemCount];
706 glyphPool = new glyph_t[glyphs.size()];
707 memcpy(glyphPool, glyphs.constData(), glyphs.size() * sizeof(glyph_t));
709 positionPool = new QFixedPoint[positions.size()];
710 memcpy(positionPool, positions.constData(), positions.size() * sizeof(QFixedPoint));
712 charPool = new QChar[chars.size()];
713 memcpy(charPool, chars.constData(), chars.size() * sizeof(QChar));
715 for (int i=0; i<itemCount; ++i) {
716 items[i] = deviceItems.at(i);
718 items[i].glyphs = glyphPool + items[i].glyphOffset;
719 items[i].glyphPositions = positionPool + items[i].positionOffset;
720 items[i].chars = charPool + items[i].charOffset;
723 needsRelayout = false;
726 QStaticTextItem::~QStaticTextItem()
728 if (m_userData != 0 && !m_userData->ref.deref())
730 m_fontEngine->ref.deref();
733 void QStaticTextItem::setFontEngine(QFontEngine *fe)
735 if (m_fontEngine != 0)
736 m_fontEngine->ref.deref();
738 if (m_fontEngine != 0)
739 m_fontEngine->ref.ref();