mainwindow.cpp Example File
^{painting/fontsampler/mainwindow.cpp}

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 #include <QtGui>

 #include "mainwindow.h"
 #include "previewdialog.h"

 MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
 {
     setupUi(this);

     sampleSizes << 32 << 24 << 16 << 14 << 12 << 8 << 4 << 2 << 1;
     markedCount = 0;
     setupFontTree();

     connect(quitAction, SIGNAL(triggered()), qApp, SLOT(quit()));
     connect(fontTree, SIGNAL(currentItemChanged(QTreeWidgetItem *, QTreeWidgetItem *)),
             this, SLOT(showFont(QTreeWidgetItem *)));
     connect(fontTree, SIGNAL(itemChanged(QTreeWidgetItem *, int)),
             this, SLOT(updateStyles(QTreeWidgetItem *, int)));

     fontTree->setItemSelected(fontTree->topLevelItem(0), true);
     showFont(fontTree->topLevelItem(0));
 }

 void MainWindow::setupFontTree()
 {
     QFontDatabase database;
     fontTree->setColumnCount(1);
     fontTree->setHeaderLabels(QStringList() << tr("Font"));

     foreach (QString family, database.families()) {
         const QStringList styles = database.styles(family);
         if (styles.isEmpty())
             continue;

         QTreeWidgetItem *familyItem = new QTreeWidgetItem(fontTree);
         familyItem->setText(0, family);
         familyItem->setCheckState(0, Qt::Unchecked);

         foreach (QString style, styles) {
             QTreeWidgetItem *styleItem = new QTreeWidgetItem(familyItem);
             styleItem->setText(0, style);
             styleItem->setCheckState(0, Qt::Unchecked);
             styleItem->setData(0, Qt::UserRole,
                 QVariant(database.weight(family, style)));
             styleItem->setData(0, Qt::UserRole + 1,
                 QVariant(database.italic(family, style)));
         }
     }
 }

 void MainWindow::on_clearAction_triggered()
 {
     QTreeWidgetItem *currentItem = fontTree->currentItem();
     foreach (QTreeWidgetItem *item, fontTree->selectedItems())
         fontTree->setItemSelected(item, false);
     fontTree->setItemSelected(currentItem, true);
 }

 void MainWindow::on_markAction_triggered()
 {
     markUnmarkFonts(Qt::Checked);
 }

 void MainWindow::on_unmarkAction_triggered()
 {
     markUnmarkFonts(Qt::Unchecked);
 }

 void MainWindow::markUnmarkFonts(Qt::CheckState state)
 {
     QList<QTreeWidgetItem *> items = fontTree->selectedItems();
     foreach (QTreeWidgetItem *item, items) {
         if (item->checkState(0) != state)
             item->setCheckState(0, state);
     }
 }

 void MainWindow::showFont(QTreeWidgetItem *item)
 {
     if (!item)
         return;

     QString family;
     QString style;
     int weight;
     bool italic;

     if (item->parent()) {
         family = item->parent()->text(0);
         style = item->text(0);
         weight = item->data(0, Qt::UserRole).toInt();
         italic = item->data(0, Qt::UserRole + 1).toBool();
     } else {
         family = item->text(0);
         style = item->child(0)->text(0);
         weight = item->child(0)->data(0, Qt::UserRole).toInt();
         italic = item->child(0)->data(0, Qt::UserRole + 1).toBool();
     }

     QString oldText = textEdit->toPlainText().trimmed();
     bool modified = textEdit->document()->isModified();
     textEdit->clear();
     textEdit->document()->setDefaultFont(QFont(family, 32, weight, italic));

     QTextCursor cursor = textEdit->textCursor();
     QTextBlockFormat blockFormat;
     blockFormat.setAlignment(Qt::AlignCenter);
     cursor.insertBlock(blockFormat);

     if (modified)
         cursor.insertText(QString(oldText));
     else
         cursor.insertText(QString("%1 %2").arg(family).arg(style));

     textEdit->document()->setModified(modified);
 }

 void MainWindow::updateStyles(QTreeWidgetItem *item, int column)
 {
     if (!item || column != 0)
         return;

     Qt::CheckState state = item->checkState(0);
     QTreeWidgetItem *parent = item->parent();

     if (parent) {

         // Only count style items.
         if (state == Qt::Checked)
             ++markedCount;
         else
             --markedCount;

         if (state == Qt::Checked &&
             parent->checkState(0) == Qt::Unchecked) {
             // Mark parent items when child items are checked.
             parent->setCheckState(0, Qt::Checked);

         } else if (state == Qt::Unchecked &&
                    parent->checkState(0) == Qt::Checked) {

             bool marked = false;
             for (int row = 0; row < parent->childCount(); ++row) {
                 if (parent->child(row)->checkState(0) == Qt::Checked) {
                     marked = true;
                     break;
                 }
             }
             // Unmark parent items when all child items are unchecked.
             if (!marked)
                 parent->setCheckState(0, Qt::Unchecked);
         }
     } else {
         int row;
         int number = 0;
         for (row = 0; row < item->childCount(); ++row) {
             if (item->child(row)->checkState(0) == Qt::Checked)
                 ++number;
         }

         // Mark/unmark all child items when marking/unmarking top-level
         // items.
         if (state == Qt::Checked && number == 0) {
             for (row = 0; row < item->childCount(); ++row) {
                 if (item->child(row)->checkState(0) == Qt::Unchecked)
                     item->child(row)->setCheckState(0, Qt::Checked);
             }
         } else if (state == Qt::Unchecked && number > 0) {
             for (row = 0; row < item->childCount(); ++row) {
                 if (item->child(row)->checkState(0) == Qt::Checked)
                     item->child(row)->setCheckState(0, Qt::Unchecked);
             }
         }
     }

     printAction->setEnabled(markedCount > 0);
     printPreviewAction->setEnabled(markedCount > 0);
 }

 void MainWindow::on_printAction_triggered()
 {
     pageMap = currentPageMap();

     if (pageMap.count() == 0)
         return;

     QPrinter printer(QPrinter::HighResolution);
     if (!setupPrinter(printer))
         return;

     int from = printer.fromPage();
     int to = printer.toPage();
     if (from <= 0 && to <= 0) {
         from = 1;
         to = pageMap.keys().count();
     }

     QProgressDialog progress(tr("Printing font samples..."), tr("&Cancel"),
                              0, pageMap.count(), this);
     progress.setWindowModality(Qt::ApplicationModal);
     progress.setWindowTitle(tr("Printing"));
     progress.setMinimum(from - 1);
     progress.setMaximum(to);

     QPainter painter;
     painter.begin(&printer);
     bool firstPage = true;

     for (int index = from - 1; index < to; ++index) {

         if (!firstPage)
             printer.newPage();

         qApp->processEvents();
         if (progress.wasCanceled())
             break;

         printPage(index, painter, printer);
         progress.setValue(index + 1);
         firstPage = false;
     }

     painter.end();
 }

 void MainWindow::on_printPreviewAction_triggered()
 {
     pageMap = currentPageMap();

     if (pageMap.count() == 0)
         return;

     QPrinter printer;

     PreviewDialog preview(printer, this);
     connect(&preview,
         SIGNAL(pageRequested(int, QPainter &, QPrinter &)),
         this, SLOT(printPage(int, QPainter &, QPrinter &)),
         Qt::DirectConnection);

     preview.setNumberOfPages(pageMap.keys().count());
     preview.exec();
 }

 QMap<QString, StyleItems> MainWindow::currentPageMap()
 {
     QMap<QString, StyleItems> pageMap;

     for (int row = 0; row < fontTree->topLevelItemCount(); ++row) {
         QTreeWidgetItem *familyItem = fontTree->topLevelItem(row);
         QString family;

         if (familyItem->checkState(0) == Qt::Checked) {
             family = familyItem->text(0);
             pageMap[family] = StyleItems();
         }

         for (int childRow = 0; childRow < familyItem->childCount(); ++childRow) {
             QTreeWidgetItem *styleItem = familyItem->child(childRow);
             if (styleItem->checkState(0) == Qt::Checked)
                 pageMap[family].append(styleItem);
         }
     }

     return pageMap;
 }

 bool MainWindow::setupPrinter(QPrinter &printer)
 {
     QPrintDialog dialog(&printer, this);
     if (dialog.exec() == QDialog::Accepted)
         return true;
     else
         return false;
 }

 void MainWindow::printPage(int index, QPainter &painter, QPrinter &printer)
 {
     QString family = pageMap.keys()[index];
     StyleItems items = pageMap[family];

     // Find the dimensions of the text on each page.
     qreal width = 0.0;
     qreal height = 0.0;
     foreach (QTreeWidgetItem *item, items) {
         QString style = item->text(0);
         int weight = item->data(0, Qt::UserRole).toInt();
         bool italic = item->data(0, Qt::UserRole + 1).toBool();

         // Calculate the maximum width and total height of the text.
         foreach (int size, sampleSizes) {
             QFont font(family, size, weight, italic);
             font = QFont(font, painter.device());
             QFontMetricsF fontMetrics(font);
             QRectF rect = fontMetrics.boundingRect(
             QString("%1 %2").arg(family).arg(style));
             width = qMax(rect.width(), width);
             height += rect.height();
         }
     }

     qreal xScale = printer.pageRect().width() / width;
     qreal yScale = printer.pageRect().height() / height;
     qreal scale = qMin(xScale, yScale);

     qreal remainingHeight = printer.pageRect().height()/scale - height;
     qreal spaceHeight = (remainingHeight/4.0) / (items.count() + 1);
     qreal interLineHeight = (remainingHeight/4.0) / (sampleSizes.count() * items.count());

     painter.save();
     painter.translate(printer.pageRect().width()/2.0, printer.pageRect().height()/2.0);
     painter.scale(scale, scale);
     painter.setBrush(QBrush(Qt::black));

     qreal x = -width/2.0;
     qreal y = -height/2.0 - remainingHeight/4.0 + spaceHeight;

     foreach (QTreeWidgetItem *item, items) {
         QString style = item->text(0);
         int weight = item->data(0, Qt::UserRole).toInt();
         bool italic = item->data(0, Qt::UserRole + 1).toBool();

         // Draw each line of text.
         foreach (int size, sampleSizes) {
             QFont font(family, size, weight, italic);
             font = QFont(font, painter.device());
             QFontMetricsF fontMetrics(font);
             QRectF rect = fontMetrics.boundingRect(QString("%1 %2").arg(
                           font.family()).arg(style));
             y += rect.height();
             painter.setFont(font);
             painter.drawText(QPointF(x, y),
                              QString("%1 %2").arg(family).arg(style));
             y += interLineHeight;
         }
         y += spaceHeight;
     }

     painter.restore();
 }