characterwidget.cpp Example File

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 #include <QtGui>

 #include "characterwidget.h"

 CharacterWidget::CharacterWidget(QWidget *parent)
     : QWidget(parent)
 {
     squareSize = 24;
     columns = 16;
     lastKey = -1;
     setMouseTracking(true);
 }

 void CharacterWidget::updateFont(const QFont &font)
 {
     displayFont.setFamily(font.family());
     squareSize = qMax(24, QFontMetrics(displayFont).xHeight() * 3);
     adjustSize();
     update();
 }

 void CharacterWidget::updateSize(const QString &fontSize)
 {
     displayFont.setPointSize(fontSize.toInt());
     squareSize = qMax(24, QFontMetrics(displayFont).xHeight() * 3);
     adjustSize();
     update();
 }

 void CharacterWidget::updateStyle(const QString &fontStyle)
 {
     QFontDatabase fontDatabase;
     const QFont::StyleStrategy oldStrategy = displayFont.styleStrategy();
     displayFont = fontDatabase.font(displayFont.family(), fontStyle, displayFont.pointSize());
     displayFont.setStyleStrategy(oldStrategy);
     squareSize = qMax(24, QFontMetrics(displayFont).xHeight() * 3);
     adjustSize();
     update();
 }

 void CharacterWidget::updateFontMerging(bool enable)
 {
     if (enable)
         displayFont.setStyleStrategy(QFont::PreferDefault);
     else
         displayFont.setStyleStrategy(QFont::NoFontMerging);
     adjustSize();
     update();
 }

 QSize CharacterWidget::sizeHint() const
 {
     return QSize(columns*squareSize, (65536/columns)*squareSize);
 }

 void CharacterWidget::mouseMoveEvent(QMouseEvent *event)
 {
     QPoint widgetPosition = mapFromGlobal(event->globalPos());
     uint key = (widgetPosition.y()/squareSize)*columns + widgetPosition.x()/squareSize;

     QString text = QString::fromLatin1("<p>Character: <span style=\"font-size: 24pt; font-family: %1\">").arg(displayFont.family())
                   + QChar(key)
                   + QString::fromLatin1("</span><p>Value: 0x")
                   + QString::number(key, 16);
     QToolTip::showText(event->globalPos(), text, this);
 }

 void CharacterWidget::mousePressEvent(QMouseEvent *event)
 {
     if (event->button() == Qt::LeftButton) {
         lastKey = (event->y()/squareSize)*columns + event->x()/squareSize;
         if (QChar(lastKey).category() != QChar::NoCategory)
             emit characterSelected(QString(QChar(lastKey)));
         update();
     }
     else
         QWidget::mousePressEvent(event);
 }

 void CharacterWidget::paintEvent(QPaintEvent *event)
 {
     QPainter painter(this);
     painter.fillRect(event->rect(), QBrush(Qt::white));
     painter.setFont(displayFont);

     QRect redrawRect = event->rect();
     int beginRow = redrawRect.top()/squareSize;
     int endRow = redrawRect.bottom()/squareSize;
     int beginColumn = redrawRect.left()/squareSize;
     int endColumn = redrawRect.right()/squareSize;

     painter.setPen(QPen(Qt::gray));
     for (int row = beginRow; row <= endRow; ++row) {
         for (int column = beginColumn; column <= endColumn; ++column) {
             painter.drawRect(column*squareSize, row*squareSize, squareSize, squareSize);
         }
     }

     QFontMetrics fontMetrics(displayFont);
     painter.setPen(QPen(Qt::black));
     for (int row = beginRow; row <= endRow; ++row) {

         for (int column = beginColumn; column <= endColumn; ++column) {

             int key = row*columns + column;
             painter.setClipRect(column*squareSize, row*squareSize, squareSize, squareSize);

             if (key == lastKey)
                 painter.fillRect(column*squareSize + 1, row*squareSize + 1, squareSize, squareSize, QBrush(Qt::red));

             painter.drawText(column*squareSize + (squareSize / 2) - fontMetrics.width(QChar(key))/2,
                              row*squareSize + 4 + fontMetrics.ascent(),
                              QString(QChar(key)));
         }
     }
 }