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# mainwindow.cpp Example File
painting/fontsampler/mainwindow.cpp

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     #include <QtGui>

     #include "mainwindow.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);
         QPrintDialog dialog(&printer, this);
         if (dialog.exec() != QDialog::Accepted)
             return;

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

         printDocument(&printer);
     }

     void MainWindow::printDocument(QPrinter *printer)
     {
         printer->setFromTo(1, pageMap.count());

         QProgressDialog progress(tr("Preparing font samples..."), tr("&Cancel"),
                                  0, pageMap.count(), this);
         progress.setWindowModality(Qt::ApplicationModal);
         progress.setWindowTitle(tr("Font Sampler"));
         progress.setMinimum(printer->fromPage() - 1);
         progress.setMaximum(printer->toPage());

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

         for (int page = printer->fromPage(); page <= printer->toPage(); ++page) {

             if (!firstPage)
                 printer->newPage();

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

             printPage(page - 1, &painter, printer);
             progress.setValue(page);
             firstPage = false;
         }

         painter.end();
     }

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

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

         QPrinter printer(QPrinter::HighResolution);
         QPrintPreviewDialog preview(&printer, this);
         connect(&preview, SIGNAL(paintRequested(QPrinter *)),
                 this, SLOT(printDocument(QPrinter *)));
         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;
     }

     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();
     }