squawk/ui/utils/textmeter.cpp

// Squawk messenger. 
// Copyright (C) 2019  Yury Gubich <blue@macaw.me>
// 
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

#include "textmeter.h"
#include <QDebug>
#include <QApplication>

TextMeter::TextMeter():
    base(),
    fonts()
{
}

TextMeter::~TextMeter()
{
}

void TextMeter::initializeFonts(const QFont& font)
{
    fonts.clear();
    QList<QFontDatabase::WritingSystem> supported = base.writingSystems(font.family());
    std::set<QFontDatabase::WritingSystem> sup;
    std::set<QString> added({font.family()});
    for (const QFontDatabase::WritingSystem& system : supported) {
        sup.insert(system);
    }
    fonts.push_back(QFontMetrics(font));
    QString style = base.styleString(font);

    QList<QFontDatabase::WritingSystem> systems = base.writingSystems();
    for (const QFontDatabase::WritingSystem& system : systems) {
        if (sup.count(system) == 0) {
            QStringList families = base.families(system);
            if (!families.empty() && added.count(families.first()) == 0) {
                QString family(families.first());
                QFont nfont = base.font(family, style, font.pointSize());
                if (added.count(nfont.family()) == 0) {
                    added.insert(family);
                    fonts.push_back(QFontMetrics(nfont));
                    qDebug() << "Added font" << nfont.family() << "for" << system;
                }
            }
        }
    }
}

QSize TextMeter::boundingSize(const QString& text, const QSize& limits) const
{
//     QString str("ridiculus mus. Suspendisse potenti. Cras pretium venenatis enim, faucibus accumsan ex");
//     bool first = true;
//     int width = 0;
//     QStringList list = str.split(" ");
//     QFontMetrics m = fonts.front();
//     for (const QString& word : list) {
//         if (first) {
//             first = false;
//         } else {
//             width += m.horizontalAdvance(QChar::Space);
//         }
//         width += m.horizontalAdvance(word);
//         for (const QChar& ch : word) {
//             width += m.horizontalAdvance(ch);
//         }
//     }
//     qDebug() << "together:" << m.horizontalAdvance(str);
//     qDebug() << "apart:" << width;
//     I cant measure or wrap text this way, this simple example shows that even this gives differen result
//     The Qt implementation under it is thousands and thousands lines of code in QTextEngine
//     I simply can't get though it

    if (text.size() == 0) {
        return QSize (0, 0);
    }
    Helper current(limits.width());
    for (const QChar& ch : text) {
        if (newLine(ch)) {
            current.computeNewWord();
            if (current.height == 0) {
                current.height = fonts.front().lineSpacing();
            }
            current.beginNewLine();
        } else if (visible(ch)) {
            bool found = false;
            for (const QFontMetrics& metrics : fonts) {
                if (metrics.inFont(ch)) {
                    current.computeChar(ch, metrics);
                    found = true;
                    break;
                }
            }

            if (!found) {
                current.computeChar(ch, fonts.front());
            }
        }
    }
    current.computeNewWord();
    current.beginNewLine();

    int& height = current.size.rheight();
    if (height > 0) {
        height -= fonts.front().leading();
    }

    return current.size;
}

void TextMeter::Helper::computeChar(const QChar& ch, const QFontMetrics& metrics)
{
    int ha = metrics.horizontalAdvance(ch);
    if (newWord(ch)) {
        if (printOnLineBreak(ch)) {
            if (!lineOverflow(metrics, ha, ch)){
                computeNewWord();
            }
        } else {
            computeNewWord();
            delayedSpaceWidth = ha;
            lastSpace = ch;
        }
    } else {
        lineOverflow(metrics, ha, ch);
    }
}

void TextMeter::Helper::computeNewLine(const QFontMetrics& metrics, int horizontalAdvance, const QChar& ch)
{
    if (wordBeganWithTheLine) {
        text = word.chopped(1);
        width = wordWidth - horizontalAdvance;
        height = wordHeight;
    }
    if (width != metrics.horizontalAdvance(text)) {
        qDebug() << "Kerning Error" << width - metrics.horizontalAdvance(text);
    }
    beginNewLine();
    if (wordBeganWithTheLine) {
        word = ch;
        wordWidth = horizontalAdvance;
        wordHeight = metrics.lineSpacing();
    }

    wordBeganWithTheLine = true;
    delayedSpaceWidth = 0;
    lastSpace = QChar::Null;
}

void TextMeter::Helper::beginNewLine()
{
    size.rheight() += height;
    size.rwidth() = qMax(size.width(), width);
    qDebug() << text;
    text = "";
    width = 0;
    height = 0;
}

void TextMeter::Helper::computeNewWord()
{
    width += wordWidth + delayedSpaceWidth;
    height = qMax(height, wordHeight);
    if (lastSpace != QChar::Null) {
        text += lastSpace;
    }
    text += word;
    word = "";
    wordWidth = 0;
    wordHeight = 0;
    delayedSpaceWidth = 0;
    lastSpace = QChar::Null;
    wordBeganWithTheLine = false;
}

bool TextMeter::Helper::lineOverflow(const QFontMetrics& metrics, int horizontalAdvance, const QChar& ch)
{
    wordHeight = qMax(wordHeight, metrics.lineSpacing());
    wordWidth += horizontalAdvance;
    word += ch;
    if (width + delayedSpaceWidth + wordWidth > maxWidth) {
        computeNewLine(metrics, horizontalAdvance, ch);
        return true;
    }
    return false;
}


bool TextMeter::newLine(const QChar& ch)
{
    return ch == QChar::LineFeed;
}

bool TextMeter::newWord(const QChar& ch)
{
    return ch.isSpace() || ch.isPunct();
}

bool TextMeter::printOnLineBreak(const QChar& ch)
{
    return ch != QChar::Space;
}

bool TextMeter::visible(const QChar& ch)
{
    return true;
}

TextMeter::Helper::Helper(int p_maxWidth):
    width(0),
    height(0),
    wordWidth(0),
    wordHeight(0),
    delayedSpaceWidth(0),
    maxWidth(p_maxWidth),
    wordBeganWithTheLine(true),
    text(""),
    word(""),
    lastSpace(QChar::Null),
    size(0, 0)
{
}