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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>
48 #include <QtGui/qapplication.h>
54 \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 QGLWidget.
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 >= 1);
188 void QStaticText::detach()
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 Compares \a other to this QStaticText. Returns true if the texts, fonts and text widths
231 bool QStaticText::operator==(const QStaticText &other) const
233 return (data == other.data
234 || (data->text == other.data->text
235 && data->font == other.data->font
236 && data->textWidth == other.data->textWidth));
240 Compares \a other to this QStaticText. Returns true if the texts, fonts or maximum sizes
243 bool QStaticText::operator!=(const QStaticText &other) const
245 return !(*this == other);
249 Sets the text of the QStaticText to \a text.
251 \note This function will cause the layout of the text to require recalculation.
255 void QStaticText::setText(const QString &text)
263 Sets the text format of the QStaticText to \a textFormat. If \a textFormat is set to
264 Qt::AutoText (the default), the format of the text will try to be determined using the
265 function Qt::mightBeRichText(). If the text format is Qt::PlainText, then the text will be
266 displayed as is, whereas it will be interpreted as HTML if the format is Qt::RichText. HTML tags
267 that alter the font of the text, its color, or its layout are supported by QStaticText.
269 \note This function will cause the layout of the text to require recalculation.
271 \sa textFormat(), setText(), text()
273 void QStaticText::setTextFormat(Qt::TextFormat textFormat)
276 data->textFormat = textFormat;
281 Returns the text format of the QStaticText.
283 \sa setTextFormat(), setText(), text()
285 Qt::TextFormat QStaticText::textFormat() const
287 return Qt::TextFormat(data->textFormat);
291 Returns the text of the QStaticText.
295 QString QStaticText::text() const
301 Sets the performance hint of the QStaticText according to the \a
302 performanceHint provided. The \a performanceHint is used to
303 customize how much caching is done internally to improve
306 The default is QStaticText::ModerateCaching.
308 \note This function will cause the layout of the text to require recalculation.
310 \sa performanceHint()
312 void QStaticText::setPerformanceHint(PerformanceHint performanceHint)
314 if ((performanceHint == ModerateCaching && !data->useBackendOptimizations)
315 || (performanceHint == AggressiveCaching && data->useBackendOptimizations)) {
319 data->useBackendOptimizations = (performanceHint == AggressiveCaching);
324 Returns which performance hint is set for the QStaticText.
326 \sa setPerformanceHint()
328 QStaticText::PerformanceHint QStaticText::performanceHint() const
330 return data->useBackendOptimizations ? AggressiveCaching : ModerateCaching;
334 Sets the text option structure that controls the layout process to the given \a textOption.
338 void QStaticText::setTextOption(const QTextOption &textOption)
341 data->textOption = textOption;
346 Returns the current text option used to control the layout process.
348 QTextOption QStaticText::textOption() const
350 return data->textOption;
354 Sets the preferred width for this QStaticText. If the text is wider than the specified width,
355 it will be broken into multiple lines and grow vertically. If the text cannot be split into
356 multiple lines, it will be larger than the specified \a textWidth.
358 Setting the preferred text width to a negative number will cause the text to be unbounded.
360 Use size() to get the actual size of the text.
362 \note This function will cause the layout of the text to require recalculation.
364 \sa textWidth(), size()
366 void QStaticText::setTextWidth(qreal textWidth)
369 data->textWidth = textWidth;
374 Returns the preferred width for this QStaticText.
378 qreal QStaticText::textWidth() const
380 return data->textWidth;
384 Returns the size of the bounding rect for this QStaticText.
388 QSizeF QStaticText::size() const
390 if (data->needsRelayout)
392 return data->actualSize;
395 QStaticTextPrivate::QStaticTextPrivate()
396 : textWidth(-1.0), items(0), itemCount(0), glyphPool(0), positionPool(0), charPool(0),
397 needsRelayout(true), useBackendOptimizations(false), textFormat(Qt::AutoText),
398 untransformedCoordinates(false)
402 QStaticTextPrivate::QStaticTextPrivate(const QStaticTextPrivate &other)
403 : text(other.text), font(other.font), textWidth(other.textWidth), matrix(other.matrix),
404 items(0), itemCount(0), glyphPool(0), positionPool(0), charPool(0), textOption(other.textOption),
405 needsRelayout(true), useBackendOptimizations(other.useBackendOptimizations),
406 textFormat(other.textFormat), untransformedCoordinates(other.untransformedCoordinates)
410 QStaticTextPrivate::~QStaticTextPrivate()
414 delete[] positionPool;
418 QStaticTextPrivate *QStaticTextPrivate::get(const QStaticText *q)
420 return q->data.data();
425 class DrawTextItemRecorder: public QPaintEngine
428 DrawTextItemRecorder(bool untransformedCoordinates, bool useBackendOptimizations)
429 : m_dirtyPen(false), m_useBackendOptimizations(useBackendOptimizations),
430 m_untransformedCoordinates(untransformedCoordinates), m_currentColor(Qt::black)
434 virtual void updateState(const QPaintEngineState &newState)
436 if (newState.state() & QPaintEngine::DirtyPen
437 && newState.pen().color() != m_currentColor) {
439 m_currentColor = newState.pen().color();
443 virtual void drawTextItem(const QPointF &position, const QTextItem &textItem)
445 const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);
447 QStaticTextItem currentItem;
448 currentItem.setFontEngine(ti.fontEngine);
449 currentItem.font = ti.font();
450 currentItem.charOffset = m_chars.size();
451 currentItem.numChars = ti.num_chars;
452 currentItem.glyphOffset = m_glyphs.size(); // Store offset into glyph pool
453 currentItem.positionOffset = m_glyphs.size(); // Offset into position pool
454 currentItem.useBackendOptimizations = m_useBackendOptimizations;
456 currentItem.color = m_currentColor;
458 QTransform matrix = m_untransformedCoordinates ? QTransform() : state->transform();
459 matrix.translate(position.x(), position.y());
461 QVarLengthArray<glyph_t> glyphs;
462 QVarLengthArray<QFixedPoint> positions;
463 ti.fontEngine->getGlyphPositions(ti.glyphs, matrix, ti.flags, glyphs, positions);
465 int size = glyphs.size();
466 Q_ASSERT(size == positions.size());
467 currentItem.numGlyphs = size;
469 m_glyphs.resize(m_glyphs.size() + size);
470 m_positions.resize(m_glyphs.size());
471 m_chars.resize(m_chars.size() + ti.num_chars);
473 glyph_t *glyphsDestination = m_glyphs.data() + currentItem.glyphOffset;
474 memcpy(glyphsDestination, glyphs.constData(), sizeof(glyph_t) * currentItem.numGlyphs);
476 QFixedPoint *positionsDestination = m_positions.data() + currentItem.positionOffset;
477 memcpy(positionsDestination, positions.constData(), sizeof(QFixedPoint) * currentItem.numGlyphs);
479 QChar *charsDestination = m_chars.data() + currentItem.charOffset;
480 memcpy(charsDestination, ti.chars, sizeof(QChar) * currentItem.numChars);
482 m_items.append(currentItem);
485 virtual void drawPolygon(const QPointF *, int , PolygonDrawMode )
487 /* intentionally empty */
490 virtual bool begin(QPaintDevice *) { return true; }
491 virtual bool end() { return true; }
492 virtual void drawPixmap(const QRectF &, const QPixmap &, const QRectF &) {}
493 virtual Type type() const
498 QVector<QStaticTextItem> items() const
503 QVector<QFixedPoint> positions() const
508 QVector<glyph_t> glyphs() const
513 QVector<QChar> chars() const
519 QVector<QStaticTextItem> m_items;
520 QVector<QFixedPoint> m_positions;
521 QVector<glyph_t> m_glyphs;
522 QVector<QChar> m_chars;
525 bool m_useBackendOptimizations;
526 bool m_untransformedCoordinates;
527 QColor m_currentColor;
530 class DrawTextItemDevice: public QPaintDevice
533 DrawTextItemDevice(bool untransformedCoordinates, bool useBackendOptimizations)
535 m_paintEngine = new DrawTextItemRecorder(untransformedCoordinates,
536 useBackendOptimizations);
539 ~DrawTextItemDevice()
541 delete m_paintEngine;
544 int metric(PaintDeviceMetric m) const
555 case PdmPhysicalDpiX:
556 val = qt_defaultDpiX();
559 case PdmPhysicalDpiY:
560 val = qt_defaultDpiY();
570 qWarning("DrawTextItemDevice::metric: Invalid metric command");
575 virtual QPaintEngine *paintEngine() const
577 return m_paintEngine;
580 QVector<glyph_t> glyphs() const
582 return m_paintEngine->glyphs();
585 QVector<QFixedPoint> positions() const
587 return m_paintEngine->positions();
590 QVector<QStaticTextItem> items() const
592 return m_paintEngine->items();
595 QVector<QChar> chars() const
597 return m_paintEngine->chars();
601 DrawTextItemRecorder *m_paintEngine;
605 void QStaticTextPrivate::paintText(const QPointF &topLeftPosition, QPainter *p)
607 bool preferRichText = textFormat == Qt::RichText
608 || (textFormat == Qt::AutoText && Qt::mightBeRichText(text));
610 if (!preferRichText) {
611 QTextLayout textLayout;
612 textLayout.setText(text);
613 textLayout.setFont(font);
614 textLayout.setTextOption(textOption);
616 qreal leading = QFontMetricsF(font).leading();
617 qreal height = -leading;
619 textLayout.beginLayout();
621 QTextLine line = textLayout.createLine();
625 if (textWidth >= 0.0)
626 line.setLineWidth(textWidth);
628 line.setPosition(QPointF(0.0, height));
629 height += line.height();
631 textLayout.endLayout();
633 actualSize = textLayout.boundingRect().size();
634 textLayout.draw(p, topLeftPosition);
636 QTextDocument document;
637 #ifndef QT_NO_CSSPARSER
638 QColor color = p->pen().color();
639 document.setDefaultStyleSheet(QString::fromLatin1("body { color: #%1%2%3 }")
640 .arg(QString::number(color.red(), 16), 2, QLatin1Char('0'))
641 .arg(QString::number(color.green(), 16), 2, QLatin1Char('0'))
642 .arg(QString::number(color.blue(), 16), 2, QLatin1Char('0')));
644 document.setDefaultFont(font);
645 document.setDocumentMargin(0.0);
646 #ifndef QT_NO_TEXTHTMLPARSER
647 document.setHtml(text);
649 document.setPlainText(text);
651 if (textWidth >= 0.0)
652 document.setTextWidth(textWidth);
654 document.adjustSize();
655 document.setDefaultTextOption(textOption);
658 p->translate(topLeftPosition);
659 QAbstractTextDocumentLayout::PaintContext ctx;
660 ctx.palette.setColor(QPalette::Text, p->pen().color());
661 document.documentLayout()->draw(p, ctx);
664 if (textWidth >= 0.0)
665 document.adjustSize(); // Find optimal size
667 actualSize = document.size();
671 void QStaticTextPrivate::init()
675 delete[] positionPool;
678 position = QPointF(0, 0);
680 DrawTextItemDevice device(untransformedCoordinates, useBackendOptimizations);
682 QPainter painter(&device);
683 painter.setFont(font);
684 painter.setTransform(matrix);
686 paintText(QPointF(0, 0), &painter);
689 QVector<QStaticTextItem> deviceItems = device.items();
690 QVector<QFixedPoint> positions = device.positions();
691 QVector<glyph_t> glyphs = device.glyphs();
692 QVector<QChar> chars = device.chars();
694 itemCount = deviceItems.size();
695 items = new QStaticTextItem[itemCount];
697 glyphPool = new glyph_t[glyphs.size()];
698 memcpy(glyphPool, glyphs.constData(), glyphs.size() * sizeof(glyph_t));
700 positionPool = new QFixedPoint[positions.size()];
701 memcpy(positionPool, positions.constData(), positions.size() * sizeof(QFixedPoint));
703 charPool = new QChar[chars.size()];
704 memcpy(charPool, chars.constData(), chars.size() * sizeof(QChar));
706 for (int i=0; i<itemCount; ++i) {
707 items[i] = deviceItems.at(i);
709 items[i].glyphs = glyphPool + items[i].glyphOffset;
710 items[i].glyphPositions = positionPool + items[i].positionOffset;
711 items[i].chars = charPool + items[i].charOffset;
714 needsRelayout = false;
717 QStaticTextItem::~QStaticTextItem()
719 if (m_userData != 0 && !m_userData->ref.deref())
721 m_fontEngine->ref.deref();
724 void QStaticTextItem::setFontEngine(QFontEngine *fe)
726 if (m_fontEngine != 0)
727 m_fontEngine->ref.deref();
729 if (m_fontEngine != 0)
730 m_fontEngine->ref.ref();