QWebPage / QPrinter - can't load page - c++

Question

I am new in Qt and I need to do a program who export html page to PDF
So, the main idea is use QWebPage for interpret html and export itself to pdf with QPrinter.
I have two class webview who use QWebPage and Print who use QPrinter.
In main.cpp I have connect LoadFinished to PrintPDF slot:
Print *pdf = new Print(args);
webview *nav = new webview();
nav->setPrinter(pdf->getPrinter());
if(nav->load(args) == false) {
qDebug() << "can't load page";
return 0;
}
//when the page page is ready, we will print it
QObject::connect(nav->getFrame(), SIGNAL(loadFinished(bool)), nav, SLOT(printPDF(bool)));
My webview.cpp class:
#include "webview.h"
webview::webview()
{
page = new QWebPage;
printer = 0;
}
webview::~webview()
{
delete page;
}
bool webview::load(Arguments *args)
{
QRegularExpression url("^(file|http)://");
QRegularExpression fullPath("^/");
QRegularExpressionMatch pathMatch = fullPath.match(args->getSource());
QRegularExpressionMatch urlMatch = url.match(args->getSource());
// see http://qt-project.org/doc/qt-4.8/qwebsettings.html#WebAttribute-enum for more informations
page->settings()->setAttribute(QWebSettings::LocalStorageEnabled, true);
page->settings()->setAttribute(QWebSettings::AutoLoadImages, true);
page->settings()->setAttribute(QWebSettings::JavascriptEnabled, true);
page->settings()->setAttribute(QWebSettings::PrintElementBackgrounds, true);
page->settings()->setAttribute(QWebSettings::PluginsEnabled, true);
if(pathMatch.hasMatch()) {
page->mainFrame()->load(QUrl::fromLocalFile(args->getSource()));
} else {
if (urlMatch.hasMatch()) {
page->mainFrame()->load(QUrl(args->getSource()));
} else {
fprintf(stderr, "%s\n", qPrintable(QApplication::translate("main", "Error: Invalide source file")));
return false;
}
}
return true;
}
void webview::printPDF(bool ok)
{
if(ok == true) {
qDebug() << "okay";
} else
qDebug() << "non okay";
if(printer != 0)
page->mainFrame()->print(printer);
}
This is what my console display:
non okay
QPainter::begin: A paint device can only be painted by one painter at a time.
I have no idea where the error might be due. The whole project is here
The arguments are:
./htmltopdf http://stackoverflow.com destinationFolder
(destinationFolder is not yet implemented, you must directly modify the source code)

Answer 1

You have more than one Painter in your Code. Search for it.
I thing the Problem is in your "Printer Class". With a Local Printer in the printPDF Method it works. Try it:
void webview::printPDF(bool ok)
{
QPrinter printer(QPrinter::HighResolution);
QString fileName = QFileDialog::getSaveFileName(this, "Export PDF",
QString(), "*.pdf");
printer.setPageSize(QPrinter::A4);
printer.setOrientation(QPrinter::Portrait);
printer.setOutputFormat(QPrinter::PdfFormat);
printer.setOutputFileName(fileName);
page()->mainFrame()->print(&printer);
}
UPDATE: Here a small working Example:
testview.cpp
#include "testview.h"
#include <QWebFrame>
#include "webview.h"
#include <QWebPage>
#include <QGridLayout>
testview::testview(QWidget *parent)
: QMainWindow(parent)
{
ui.setupUi(this);
QGridLayout* Layout = new QGridLayout(this);
webview* w = new webview(this);
w->setMinimumSize(500, 500);
centralWidget()->setLayout(Layout);
bool a = connect(w->page()->mainFrame(), SIGNAL(loadFinished(bool)), w, SLOT(printPDF(bool)));
w->page()->mainFrame()->load(QUrl("http://stackoverflow.com"));
}
testview::~testview()
{
}
webview.cpp
#include "webview.h"
#include <QPrinter>
#include <QWebFrame>
#include <QFileDialog>
webview::webview(QWidget *parent)
: QWebView(parent)
{
}
webview::~webview()
{
}
void webview::printPDF(bool ok)
{
QPrinter printer(QPrinter::HighResolution);
QString fileName = QFileDialog::getSaveFileName(this, "Export PDF",
QString(), "*.pdf");
printer.setPageSize(QPrinter::A4);
printer.setOrientation(QPrinter::Portrait);
printer.setOutputFormat(QPrinter::PdfFormat);
printer.setOutputFileName(fileName);
page()->mainFrame()->print(&printer);
}

Answer 2

The problem was elsewhere :
In my main.cpp I had this :
QObject::connect(nav->getFrame(), SIGNAL(loadFinished(bool)), nav, SLOT(printPDF(bool)));
[...]
delete args;
delete pdf;
delete nav;
return app.exec();
app.exec() is a kind of infinit loop who thaht handles Qt events and thus allows the program does not close.
If I proceed to delete before calling this function,then I will have freshly deallocated pointers that will be used
If I Do :
bool result = app.exec();
delete args;
delete pdf;
delete nav;
return result;
It's work fine !