KDReportsFontScaler.cpp

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/****************************************************************************
**
** This file is part of the KD Reports library.
**
** SPDX-FileCopyrightText: 2007-2022 Klarälvdalens Datakonsult AB, a KDAB Group company <info@kdab.com>
**
** SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDAB-KDReports OR LicenseRef-KDAB-KDReports-US
**
** Licensees holding valid commercial KD Reports licenses may use this file in
** accordance with the KD Reports Commercial License Agreement provided with
** the Software.
**
** Contact info@kdab.com if any conditions of this licensing are not clear to you.
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****************************************************************************/
 
#include "KDReportsFontScaler_p.h"
#include <QDebug>
#include <QFont>
#include <QFontMetricsF>
 
using namespace KDReports;
 
FontScaler::FontScaler(const QFont &initialFont)
    : m_font(initialFont)
    , m_fontMetrics(m_font)
    , m_initialFontMetrics(m_fontMetrics)
    , m_scalingFactor(1.0)
{
}
 
void FontScaler::setFontAndScalingFactor(const QFont &font, qreal scalingFactor)
{
#ifdef DEBUG_LAYOUT
    // qDebug() << "setFontAndScalingFactor scalingFactor=" << scalingFactor;
#endif
    m_font = font;
    m_scalingFactor = scalingFactor;
    if (m_font.pixelSize() == -1)
        m_font.setPointSizeF(m_font.pointSizeF() * scalingFactor);
    else
        m_font.setPixelSize(qRound(m_font.pixelSize() * scalingFactor));
    m_fontMetrics = QFontMetricsF(m_font);
    m_initialFontMetrics = m_fontMetrics;
}
 
void FontScaler::applyAdditionalScalingFactor(qreal factor)
{
    // TODO this should be calculated in the end, using finalWidth/initialWidth. It's currently messed up by the -0.1 below for instance.
    m_scalingFactor *= factor;
 
    if (m_font.pixelSize() == -1) {
        if (factor > 0.99 && factor < 1.000) // applying 0.999 forever can take a very long time ;)
            m_font.setPointSizeF(m_font.pointSizeF() - 0.1);
        else
            m_font.setPointSizeF(m_font.pointSizeF() * factor);
    } else {
        if (m_font.pixelSize() > 2 && factor > 0.99 && factor < 1.000)
            m_font.setPixelSize(m_font.pixelSize() - 1);
        else
            m_font.setPixelSize(int(m_font.pixelSize() * factor));
    }
#ifdef DEBUG_LAYOUT
    qDebug() << " applyAdditionalScalingFactor" << factor << "combined factor:" << m_scalingFactor << "pointSize:" << m_font.pointSizeF() << "pixelSize:" << m_font.pixelSize();
#endif
    m_fontMetrics = QFontMetricsF(m_font);
}
 
static qreal textWidthForMetrics(const QFontMetricsF &fm, const QString &text)
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    return fm.width(text);
#else
    return fm.size(Qt::TextSingleLine, text).width();
#endif
}
 
qreal FontScaler::textWidth(const QString &text) const
{
    return textWidthForMetrics(m_fontMetrics, text);
}
 
void FontScaler::setFactorForHeight(qreal wantedHeight)
{
#ifdef DEBUG_LAYOUT
    qDebug() << " FontScaler::setFactorForHeight" << wantedHeight;
#endif
    Q_ASSERT(wantedHeight > 0);
    qreal height = m_fontMetrics.height();
    int iterations = 0;
 
    while (height > wantedHeight && height > 3.0 /* seems to be the min we can get */) {
        const qreal factor = wantedHeight / height;
        applyAdditionalScalingFactor(factor);
        qreal prevHeight = height;
        height = m_fontMetrics.height();
#ifdef DEBUG_LAYOUT
        qDebug() << " FontScaler: height=" << height << factor << m_scalingFactor;
#endif
        if (++iterations > 10 && height == prevHeight) {
            // We're not getting anywhere, probably we're hitting a minimum width when
            // trying to use a very, very small font (see unittest testFontScalerVerySmall)
            break;
        }
        if (m_font.pixelSize() == 1) {
            break;
        }
    }
}
 
void FontScaler::setFactorForWidth(qreal wantedFactor, const QString &sampleText)
{
#ifdef DEBUG_LAYOUT
    qDebug() << " FontScaler::setFactorForWidth" << wantedFactor;
#endif
    // Just applying that scaling factor for the font size isn't enough,
    // fonts do not scale proportionnally. We need do this like
    // "scale the font so that this text fits into this width"
    const qreal initialWidth = textWidthForMetrics(m_initialFontMetrics, sampleText);
    const qreal wantedWidth = initialWidth * wantedFactor;
    qreal width = textWidth(sampleText);
#ifdef DEBUG_LAYOUT
    qDebug() << " FontScaler: sampleText with initialFontMetrics:" << initialWidth << "with current fontMetrics:" << width << "wanted:" << wantedWidth;
#endif
 
    int iterations = 0;
 
    while (width > wantedWidth) {
        qreal factor = wantedWidth / width;
        applyAdditionalScalingFactor(factor);
        qreal prevWidth = width;
        width = textWidth(sampleText);
#ifdef DEBUG_LAYOUT
        qDebug() << "  FontScaler: width=" << width << "factor=" << factor << "m_scalingFactor=" << m_scalingFactor;
#endif
        if (++iterations > 10 && width == prevWidth) {
            // We're not getting anywhere, probably we're hitting a minimum width when
            // trying to use a very, very small font (see unittest testFontScalerVerySmall)
            break;
        }
    }
}