qwt_plot_textlabel.cpp

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/* -*- mode: C++ ; c-file-style: "stroustrup" -*- *****************************
 * Qwt Widget Library
 * Copyright (C) 1997   Josef Wilgen
 * Copyright (C) 2002   Uwe Rathmann
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the Qwt License, Version 1.0
 *****************************************************************************/

#include "qwt_plot_textlabel.h"
#include "qwt_painter.h"
#include "qwt_text.h"
#include "qwt_math.h"

#include <qpainter.h>
#include <qpaintengine.h>
#include <qpixmap.h>

static QRect qwtItemRect( int renderFlags,
    const QRectF &rect, const QSizeF &itemSize )
{
    int x;
    if ( renderFlags & Qt::AlignLeft )
    {
        x = rect.left();
    }
    else if ( renderFlags & Qt::AlignRight )
    {
        x = rect.right() - itemSize.width();
    }
    else
    {
        x = rect.center().x() - 0.5 * itemSize.width();
    }

    int y;
    if ( renderFlags & Qt::AlignTop )
    {
        y = rect.top();
    }
    else if ( renderFlags & Qt::AlignBottom )
    {
        y = rect.bottom() - itemSize.height();
    }
    else
    {
        y = rect.center().y() - 0.5 * itemSize.height();
    }

    return QRect( x, y, itemSize.width(), itemSize.height() );
}

class QwtPlotTextLabel::PrivateData
{
public:
    PrivateData():
        margin( 5 )
    {
    }

    QwtText text;
    int margin;

    QPixmap pixmap;
};

QwtPlotTextLabel::QwtPlotTextLabel():
    QwtPlotItem( QwtText( "Label" ) )
{
    d_data = new PrivateData;

    setItemAttribute( QwtPlotItem::AutoScale, false );
    setItemAttribute( QwtPlotItem::Legend, false );

    setZ( 150 );
}

QwtPlotTextLabel::~QwtPlotTextLabel()
{
    delete d_data;
}

int QwtPlotTextLabel::rtti() const
{
    return QwtPlotItem::Rtti_PlotTextLabel;
}

void QwtPlotTextLabel::setText( const QwtText &text )
{
    if ( d_data->text != text )
    {
        d_data->text = text;

        invalidateCache();
        itemChanged();
    }
}

QwtText QwtPlotTextLabel::text() const
{
    return d_data->text;
}

void QwtPlotTextLabel::setMargin( int margin )
{
    margin = qMax( margin, 0 );
    if ( d_data->margin != margin )
    {
        d_data->margin = margin;
        itemChanged();
    }
}

int QwtPlotTextLabel::margin() const
{
    return d_data->margin;
}

void QwtPlotTextLabel::draw( QPainter *painter,
    const QwtScaleMap &xMap, const QwtScaleMap &yMap,
    const QRectF &canvasRect ) const
{
    Q_UNUSED( xMap );
    Q_UNUSED( yMap );

    const int m = d_data->margin;

    const QRectF rect = textRect( canvasRect.adjusted( m, m, -m, -m ),
        d_data->text.textSize( painter->font() ) );

    bool doCache = QwtPainter::roundingAlignment( painter );
    if ( doCache )
    {
        switch( painter->paintEngine()->type() )
        {
            case QPaintEngine::Picture:
            case QPaintEngine::User: // usually QwtGraphic
            {
                // don't use a cache for record/replay devices
                doCache = false;
                break;
            }
            default:;
        }
    }

    if ( doCache )
    {
        // when the paint device is aligning it is not one
        // where scalability matters ( PDF, SVG ).
        // As rendering a text label is an expensive operation
        // we use a cache.

        int pw = 0;
        if ( d_data->text.borderPen().style() != Qt::NoPen )
            pw = qMax( d_data->text.borderPen().width(), 1 );

        QRect pixmapRect;
        pixmapRect.setLeft( qwtFloor( rect.left() ) - pw );
        pixmapRect.setTop( qwtFloor( rect.top() ) - pw );
        pixmapRect.setRight( qwtCeil( rect.right() ) + pw );
        pixmapRect.setBottom( qwtCeil( rect.bottom() ) + pw );

#if QT_VERSION >= 0x050000
        const qreal pixelRatio = QwtPainter::devicePixelRatio( painter->device() );
        const QSize scaledSize = pixmapRect.size() * pixelRatio;
#else
        const QSize scaledSize = pixmapRect.size();
#endif

        if ( d_data->pixmap.isNull() ||
            ( scaledSize != d_data->pixmap.size() )  )
        {
            d_data->pixmap = QPixmap( scaledSize );
#if QT_VERSION >= 0x050000
            d_data->pixmap.setDevicePixelRatio( pixelRatio );
#endif
            d_data->pixmap.fill( Qt::transparent );

            const QRect r( pw, pw,
                pixmapRect.width() - 2 * pw, pixmapRect.height() - 2 * pw );

            QPainter pmPainter( &d_data->pixmap );
            d_data->text.draw( &pmPainter, r );
        }

        painter->drawPixmap( pixmapRect, d_data->pixmap );
    }
    else
    {
        d_data->text.draw( painter, rect );
    }
}

QRectF QwtPlotTextLabel::textRect(
    const QRectF &rect, const QSizeF &textSize ) const
{
    return qwtItemRect( d_data->text.renderFlags(), rect, textSize );
}

void QwtPlotTextLabel::invalidateCache()
{
    d_data->pixmap = QPixmap();
}