Print: improve table printing by using QTableView

The current QTextDocument implementation is slow due to
HTML parsing. By using QTableView with QAbstractTableModel
we boost the performance of the table print drastically.
This patch completely replaces the old solution.

There is a hidden QTableView widget which is populated
with all data and rendered using a QPainter attached to
the printer device.

A couple of new classes are added in models.h/cpp
that handle the table print model and these are then used
in printlayout.h/cpp.

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

1 files changed, 100 insertions, 123 deletions

diff --git a/qt-ui/printlayout.cpp b/qt-ui/printlayout.cpp
index 7061f082b..7a4944ede 100644
--- a/qt-ui/printlayout.cpp
+++ b/qt-ui/printlayout.cpp
@@ -1,9 +1,10 @@
+#include <QtCore/qmath.h>
 #include <QDebug>
 #include <QPainter>
 #include <QDesktopWidget>
 #include <QApplication>
-#include <QTextDocument>
-#include <QAbstractTextDocumentLayout>
+#include <QTableView>
+#include <QHeaderView>
 #include "mainwindow.h"
 #include "profilegraphics.h"
 #include "printlayout.h"
@@ -21,8 +22,6 @@ struct options {
 };
 */
 
-#define TABLE_PRINT_COL 7
-
 PrintLayout::PrintLayout(PrintDialog *dialogPtr, QPrinter *printerPtr, struct options *optionsPtr)
 {
 	dialog = dialogPtr;
@@ -30,20 +29,21 @@ PrintLayout::PrintLayout(PrintDialog *dialogPtr, QPrinter *printerPtr, struct op
 	printOptions = optionsPtr;
 
 	// table print settings
-	tableColumnNames.append(tr("Dive#"));
-	tableColumnNames.append(tr("Date"));
-	tableColumnNames.append(tr("Depth"));
-	tableColumnNames.append(tr("Duration"));
-	tableColumnNames.append(tr("Master"));
-	tableColumnNames.append(tr("Buddy"));
-	tableColumnNames.append(tr("Location"));
-	tableColumnWidths.append("7");
-	tableColumnWidths.append("10");
-	tableColumnWidths.append("10");
-	tableColumnWidths.append("10");
-	tableColumnWidths.append("15");
-	tableColumnWidths.append("15");
-	tableColumnWidths.append("100");
+	tablePrintHeadingBackground = 0xffeeeeee;
+	tablePrintColumnNames.append(tr("Dive#"));
+	tablePrintColumnNames.append(tr("Date"));
+	tablePrintColumnNames.append(tr("Depth"));
+	tablePrintColumnNames.append(tr("Duration"));
+	tablePrintColumnNames.append(tr("Master"));
+	tablePrintColumnNames.append(tr("Buddy"));
+	tablePrintColumnNames.append(tr("Location"));
+	tablePrintColumnWidths.append(7);
+	tablePrintColumnWidths.append(10);
+	tablePrintColumnWidths.append(10);
+	tablePrintColumnWidths.append(10);
+	tablePrintColumnWidths.append(15);
+	tablePrintColumnWidths.append(15);
+	tablePrintColumnWidths.append(33);
 }
 
 void PrintLayout::print()
@@ -74,6 +74,10 @@ void PrintLayout::setup()
 
 	scaleX = (qreal)printerDpi/(qreal)screenDpiX;
 	scaleY = (qreal)printerDpi/(qreal)screenDpiY;
+
+	// a printer page scalled to screen DPI
+	scaledPageW = pageRect.width() / scaleX;
+	scaledPageH = pageRect.height() / scaleY;
 }
 
 // experimental
@@ -90,7 +94,7 @@ void PrintLayout::printSixDives() const
 	profile->clear();
 	profile->setPrintMode(true, !printOptions->color_selected);
 	QSize originalSize = profile->size();
-	profile->resize(pageRect.height()/scaleY, pageRect.width()/scaleX);
+	profile->resize(scaledPageW, scaledPageH);
 
 	int i;
 	struct dive *dive;
@@ -122,127 +126,100 @@ void PrintLayout::printTwoDives() const
 	// nop
 }
 
-void PrintLayout::printTable() const
+void PrintLayout::printTable()
 {
-	QTextDocument doc;
-	QSizeF pageSize;
-	pageSize.setWidth(pageRect.width());
-	pageSize.setHeight(pageRect.height());
-	doc.documentLayout()->setPaintDevice(printer);
-	doc.setPageSize(pageSize);
-
-	QString styleSheet(
-		"<style type='text/css'>"
-		"table {"
-		"	border-width: 1px;"
-		"	border-style: solid;"
-		"	border-color: #999999;"
-		"}"
-		"th {"
-		"	background-color: #eeeeee;"
-		"	font-size: small;"
-		"	padding: 3px 5px 3px 5px;"
-		"}"
-		"td {"
-		"	font-size: small;"
-		"	padding: 3px 5px 3px 5px;"
-		"}" 
-		"</style>"
-	);
-	// setDefaultStyleSheet() doesn't work here?
-	const QString heading(insertTableHeadingRow());
-	const QString lineBreak("<br>");
-	QString htmlText = styleSheet + "<table cellspacing='0' width='100%'>";
-	QString htmlTextPrev;
-	int pageCountNew = 1, pageCount = 0, lastPageWithHeading = 0;
-	bool insertHeading = true;
-
-	int i;
+	// create and setup a table
+	QTableView table;
+	table.setAttribute(Qt::WA_DontShowOnScreen);
+	table.setSelectionMode(QAbstractItemView::NoSelection);
+	table.setFocusPolicy(Qt::NoFocus);
+	table.horizontalHeader()->setVisible(false);
+	table.horizontalHeader()->setResizeMode(QHeaderView::Fixed);
+	table.verticalHeader()->setVisible(false);
+	table.verticalHeader()->setResizeMode(QHeaderView::ResizeToContents);
+	table.setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+	table.setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
+	// fit table to one page initially
+	table.resize(scaledPageW,  scaledPageH);
+
+	// create and fill a table model
+	TablePrintModel model;
 	struct dive *dive;
+	int i, row = 0;
+	addTablePrintHeadingRow(&model, row); // add one heading row
+	row++;
 	for_each_dive(i, dive) {
 		if (!dive->selected && printOptions->print_selected)
 			continue;
-		if (insertHeading) {
-			htmlTextPrev = htmlText;
-			htmlText += heading;
-			doc.setHtml(htmlText);
-			pageCount = doc.pageCount();
-			// prevent adding two headings on the same page
-			if (pageCount == lastPageWithHeading) {
-				htmlText = htmlTextPrev;
-				// add line breaks until a new page is reached
-				while (pageCount == lastPageWithHeading) {
-					htmlTextPrev = htmlText;
-					htmlText += lineBreak;
-					doc.setHtml(htmlText);
-					pageCount = doc.pageCount();
-				}
-				// revert last line break from the new page and add heading
-				htmlText = htmlTextPrev;
-				htmlText += heading;
-			}
-			insertHeading = false;
-			lastPageWithHeading = pageCount;
-		}
-		htmlTextPrev = htmlText;
-		htmlText += insertTableDataRow(dive);
-		doc.setHtml(htmlText);
-		pageCount = pageCountNew;
-		pageCountNew = doc.pageCount();
-		// if the page count increases revert and add heading instead
-		if (pageCountNew > pageCount) {
-			htmlText = htmlTextPrev;
-			insertHeading = true;
+		addTablePrintDataRow(&model, row, dive);
+		row++;
+	}
+	table.setModel(&model); // set model to table
+	// resize columns to percentages from page width
+	for (int i = 0; i < model.columns; i++) {
+		int pw = qCeil((qreal)(tablePrintColumnWidths.at(i) * table.width()) / 100);
+		table.horizontalHeader()->resizeSection(i, pw);
+	}
+	// reset the model at this point
+	model.callReset();
+
+	// a list of vertical offsets where pages begin and some helpers
+	QList<unsigned int> pageIndexes;
+	pageIndexes.append(0);
+	int tableHeight = 0, rowH = 0, accH = 0;
+
+	// process all rows
+	for (int i = 0; i < model.rows; i++) {
+		rowH = table.rowHeight(i);
+		accH += rowH;
+		if (accH > scaledPageH) { // push a new page index and add a heading
+			pageIndexes.append(pageIndexes.last() + (accH - rowH));
+			addTablePrintHeadingRow(&model, i);
+			accH = 0;
 			i--;
 		}
+		tableHeight += rowH;
 	}
-	htmlText += "</table>";
-	doc.setHtml(htmlText);
-	doc.print(printer);
-}
+	pageIndexes.append(pageIndexes.last() + accH);
+	// resize the whole widget so that it can be rendered
+	table.resize(scaledPageW, tableHeight);
 
-QString PrintLayout::insertTableHeadingRow() const
-{
-	int i;
-	QString ret("<tr>");
-	for (i = 0; i < TABLE_PRINT_COL; i++)
-		ret += insertTableHeadingCol(i);
-	ret += "</tr>";
-	return ret;
-}
-
-QString PrintLayout::insertTableHeadingCol(int col) const
-{
-	QString ret("<th align='left' width='");
-	ret += tableColumnWidths.at(col);
-	ret += "%'>";
-	ret += tableColumnNames.at(col);
-	ret += "</th>";
-	return ret;
+	// attach a painter and render pages by using pageIndexes
+	QPainter painter(printer);
+	painter.setRenderHint(QPainter::Antialiasing);
+	painter.setRenderHint(QPainter::SmoothPixmapTransform);
+	painter.scale(scaleX, scaleY);
+	for (int i = 0; i < pageIndexes.size() - 1; i++) {
+		if (i > 0)
+			printer->newPage();
+		QRegion region(0, pageIndexes.at(i) - 1,
+		               table.width(),
+		               pageIndexes.at(i + 1) - pageIndexes.at(i) + 2);
+		table.render(&painter, QPoint(0, 0), region);
+	}
 }
 
-QString PrintLayout::insertTableDataRow(struct dive *dive) const
+void PrintLayout::addTablePrintDataRow(TablePrintModel *model, int row, struct dive *dive) const
 {
-	// use the DiveItem class
 	struct DiveItem di;
 	di.dive = dive;
-
-	// fill row
-	QString ret("<tr>");
-	ret += insertTableDataCol(QString::number(dive->number));
-	ret += insertTableDataCol(di.displayDate());
-	ret += insertTableDataCol(di.displayDepth());
-	ret += insertTableDataCol(di.displayDuration());
-	ret += insertTableDataCol(dive->divemaster);
-	ret += insertTableDataCol(dive->buddy);
-	ret += insertTableDataCol(dive->location);
-	ret += "</tr>";
-	return ret;
+	model->insertRow();
+	model->setData(model->index(row, 0), QString::number(dive->number), Qt::DisplayRole);
+	model->setData(model->index(row, 1), di.displayDate(), Qt::DisplayRole);
+	model->setData(model->index(row, 2), di.displayDepth(), Qt::DisplayRole);
+	model->setData(model->index(row, 3), di.displayDuration(), Qt::DisplayRole);
+	model->setData(model->index(row, 4), dive->divemaster, Qt::DisplayRole);
+	model->setData(model->index(row, 5), dive->buddy, Qt::DisplayRole);
+	model->setData(model->index(row, 6), dive->location, Qt::DisplayRole);
 }
 
-QString PrintLayout::insertTableDataCol(QString data) const
+void PrintLayout::addTablePrintHeadingRow(TablePrintModel *model, int row) const
 {
-	return "<td>" + data + "</td>";
+	model->insertRow(row);
+	for (int i = 0; i < model->columns; i++) {
+		model->setData(model->index(row, i), tablePrintColumnNames.at(i), Qt::DisplayRole);
+		model->setData(model->index(row, i), tablePrintHeadingBackground, Qt::BackgroundRole);
+	}
 }
 
 // experimental