如何從 QWebEngineView 打印
[英]How to print from QWebEngineView
問題描述
我正在嘗試從我的應用程序中打印一份報告，其中涉及文本和表格。 由於QTextDocument不夠用，我決定使用QWebEngineView和更復雜的 HTML/CSS，但 Qt 富文本引擎不支持。
我能夠從視圖創建 PDF，但是我有一些普遍的誤解，因為有時它會崩潰，並且打印而不是 PDF 創建會崩潰。
這是我的嘗試：
方法一：PDF創建
這是唯一的工作變體：
auto webView = new QWebEngineView();
webView->setHtml(contents);
const QString fn = QFileDialog::getSaveFileName(0, "Save pdf", ".", "PDF Files (*.pdf)");
if (!fn.isEmpty())
webView->page()->printToPdf(fn);
但是，這僅適用於對話框（？！）。 如果我像這樣改變它：
QString fn ="/Users/s710/Downloads/test.pdf";
auto webView = new QWebEngineView();
webView->setHtml(contents);
webView->page()->printToPdf(fn);
它將創建一個帶有空白頁面的 PDF。 所以我想以上只是偶然地起作用。
方法二：直接打印
這種方法崩潰了：
auto webView = new QWebEngineView();
webView->setHtml(contents);
QPrinter printer(QPrinter::QPrinter::ScreenResolution);
printer.setOutputFormat(QPrinter::NativeFormat);
printer.setPaperSize(QPrinter::A4);
printer.setPageMargins(12, 16, 12, 20, QPrinter::Millimeter);
webView->page()->print(&printer, [](bool){});
Crash:
1 QPrinter::pageRect() const (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtPrintSupport.framework/Versions/5/QtPrintSupport 0x100247fe4
2 QWebEnginePagePrivate::didPrintPage(unsigned long long, QByteArray const&) (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtWebEngineWidgets.framework/Versions/5/QtWebEngineWidgets 0x100200f0a
3 QtWebEngineCore::callbackOnPrintingFinished(QtWebEngineCore::WebContentsAdapterClient *, int, std::vector<char> const&) (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtWebEngineCore.framework/Versions/5/QtWebEngineCore 0x100899693
4 base::debug::TaskAnnotator::RunTask(const char *, base::PendingTask *) (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtWebEngineCore.framework/Versions/5/QtWebEngineCore 0x10295d402
5 base::MessageLoop::RunTask(base::PendingTask *) (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtWebEngineCore.framework/Versions/5/QtWebEngineCore 0x10298395f
6 base::MessageLoop::DoWork() (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtWebEngineCore.framework/Versions/5/QtWebEngineCore 0x102983ef9
7 std::__function::__func<QtWebEngineCore::(anonymous namespace)::MessagePumpForUIQt::MessagePumpForUIQt()::'lambda'(), std::allocator<QtWebEngineCore::(anonymous namespace)::MessagePumpForUIQt::MessagePumpForUIQt()::'lambda'()>, void ()>::operator()() (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtWebEngineCore.framework/Versions/5/QtWebEngineCore 0x100839f99
8 QObject::event(QEvent *) (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtCore.framework/Versions/5/QtCore 0x10824bcf6
...
方法三：等待webview加載完成，然后創建PDF
因此，由於似乎與阻止文件對話框有所不同，我認為當視圖尚未加載 HTML 時可能會出現問題。 我還讀到QWebEngineView資源繁重，所以我想我可以等待它完成加載。
但是，這也會崩潰
auto webView = new QWebEngineView();
QObject::connect(webView, &QWebEngineView::loadFinished, this, [&webView](bool ok)
{
QString fn ="/Users/s710/Downloads/test.pdf";
webView->page()->printToPdf(fn);
});
webView->setHtml(contents);
Crash:
1 QWebEnginePage::printToPdf(QString const&, QPageLayout const&) (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtWebEngineWidgets.framework/Versions/5/QtWebEngineWidgets 0x100204cd7
2 Printer::print(MonthItem *, QWidget *)::$_0::operator()(bool) const printer.cpp 203 0x100016eeb
3 QtPrivate::FunctorCall<QtPrivate::IndexesList<0>, QtPrivate::List<bool>, void, Printer::print(MonthItem *, QWidget *)::$_0>::call(Printer::print(MonthItem *, QWidget *)::$_0&, void * *) qobjectdefs_impl.h 146 0x100016dc8
4 void QtPrivate::Functor<Printer::print(MonthItem *, QWidget *)::$_0, 1>::call<QtPrivate::List<bool>, void>(Printer::print(MonthItem *, QWidget *)::$_0&, void *, void * *) qobjectdefs_impl.h 256 0x100016d71
5 QtPrivate::QFunctorSlotObject<Printer::print(MonthItem *, QWidget *)::$_0, 1, QtPrivate::List<bool>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void * *, bool *) qobjectdefs_impl.h 439 0x100016d1d
6 QMetaObject::activate(QObject *, int, int, void * *) (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtCore.framework/Versions/5/QtCore 0x10825153b
7 QWebEngineView::loadFinished(bool) (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtWebEngineWidgets.framework/Versions/5/QtWebEngineWidgets 0x10020cb3f
方法四：等待webview加載完成，然后打印
這也會崩潰：
auto webView = new QWebEngineView();
QObject::connect(webView, &QWebEngineView::loadFinished, this, [&webView](bool ok)
{
QPrinter printer(QPrinter::PrinterResolution);
printer.setOutputFormat(QPrinter::NativeFormat);
printer.setPaperSize(QPrinter::A4);
printer.setPageMargins(12, 16, 12, 20, QPrinter::Millimeter);
webView->page()->print(&printer, [](bool){});
});
webView->setHtml(contents);
Crash:
1 QWebEngineView::page() const (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtWebEngineWidgets.framework/Versions/5/QtWebEngineWidgets 0x10020f05d
2 Printer::print(MonthItem *, QWidget *)::$_0::operator()(bool) const printer.cpp 207 0x100016b35
3 QtPrivate::FunctorCall<QtPrivate::IndexesList<0>, QtPrivate::List<bool>, void, Printer::print(MonthItem *, QWidget *)::$_0>::call(Printer::print(MonthItem *, QWidget *)::$_0&, void * *) qobjectdefs_impl.h 146 0x100016a88
4 void QtPrivate::Functor<Printer::print(MonthItem *, QWidget *)::$_0, 1>::call<QtPrivate::List<bool>, void>(Printer::print(MonthItem *, QWidget *)::$_0&, void *, void * *) qobjectdefs_impl.h 256 0x100016a31
5 QtPrivate::QFunctorSlotObject<Printer::print(MonthItem *, QWidget *)::$_0, 1, QtPrivate::List<bool>, void>::impl(int, QtPrivate::QSlotObjectBase *, QObject *, void * *, bool *) qobjectdefs_impl.h 439 0x1000169dd
6 QMetaObject::activate(QObject *, int, int, void * *) (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtCore.framework/Versions/5/QtCore 0x10825353b
7 QWebEngineView::loadFinished(bool) (x86_64) /Users/s710/Qt/5.12.6/clang_64/lib/QtWebEngineWidgets.framework/Versions/5/QtWebEngineWidgets 0x10020eb3f
所以我覺得很愚蠢，因為到處都是崩潰的，但我不知道哪里出了問題。 有人可以指出我使用QWebEngineView的工作打印功能嗎？
1 個解決方案
解決方案1
2 已采納 2019-12-10 21:51:54
在第一種方法中，我認為它失敗了，因為 HTML 或 url 尚未加載並且您想要打印文本，因此可能的解決方案是使用 loadFinished 信號開始打印並使用 pdfPrintingFinished 知道打印何時完成。
#include <QtWebEngineWidgets>
class Widget : public QWidget
{
public:
explicit Widget(QWidget *parent = nullptr):
QWidget(parent), button(new QPushButton), progressbar(new QProgressBar), view(new QWebEngineView)
{
button->setText(tr("Press me"));
button->setEnabled(false);
connect(button, &QPushButton::clicked, this, &Widget::onClicked);
connect(view, &QWebEngineView::loadFinished, this, &Widget::onLoadFinished);
connect(view->page(), &QWebEnginePage::pdfPrintingFinished, this, &Widget::onPdfPrintingFinished);
QString html = R"(<!DOCTYPE html>
<html>
<head>
<style>
table {
font-family: arial, sans-serif;
border-collapse: collapse;
width: 100%;
}
td, th {
border: 1px solid #dddddd;
text-align: left;
padding: 8px;
}
tr:nth-child(even) {
background-color: #dddddd;
}
</style>
</head>
<body>
<h2>HTML Table</h2>
<table>
<tr>
<th>Company</th>
<th>Contact</th>
<th>Country</th>
</tr>
<tr>
<td>Alfreds Futterkiste</td>
<td>Maria Anders</td>
<td>Germany</td>
</tr>
<tr>
<td>Centro comercial Moctezuma</td>
<td>Francisco Chang</td>
<td>Mexico</td>
</tr>
<tr>
<td>Ernst Handel</td>
<td>Roland Mendel</td>
<td>Austria</td>
</tr>
<tr>
<td>Island Trading</td>
<td>Helen Bennett</td>
<td>UK</td>
</tr>
<tr>
<td>Laughing Bacchus Winecellars</td>
<td>Yoshi Tannamuri</td>
<td>Canada</td>
</tr>
<tr>
<td>Magazzini Alimentari Riuniti</td>
<td>Giovanni Rovelli</td>
<td>Italy</td>
</tr>
</table>
</body>
</html>
)";
view->setHtml(html);
auto lay = new QVBoxLayout(this);
lay->addWidget(button);
lay->addWidget(progressbar);
lay->addWidget(view);
resize(640, 480);
}
private:
void onLoadFinished(bool ok){
button->setEnabled(ok);
}
void onClicked(){
progressbar->setRange(0, 0);
QString fn = "/Users/s710/Downloads/test.pdf";
view->page()->printToPdf(fn);
}
void onPdfPrintingFinished(const QString & filename, bool ok){
qDebug() << filename << ok;
progressbar->setRange(0, 1);
}
private:
QPushButton *button;
QProgressBar *progressbar;
QWebEngineView *view;
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Widget w;
w.show();
return a.exec();
}
在您使用 QPrinter 的情況下，我認為導致錯誤的原因是 QPrinter 是一個局部變量，該變量在函數執行完成時被消除，但 Qt 嘗試異步訪問該變量但該對象不存在。 解決辦法是擴展QPrinter的范圍。
#include <QtWebEngineWidgets>
class Widget : public QWidget
{
public:
Widget(QWidget *parent = nullptr):
QWidget(parent), button(new QPushButton), progressbar(new QProgressBar), view(new QWebEngineView)
{
button->setText(tr("Press me"));
button->setEnabled(false);
connect(button, &QPushButton::clicked, this, &Widget::onClicked);
connect(view, &QWebEngineView::loadFinished, this, &Widget::onLoadFinished);
printer.setResolution(QPrinter::PrinterResolution);
printer.setOutputFormat(QPrinter::NativeFormat);
printer.setPaperSize(QPrinter::A4);
printer.setPageMargins(12, 16, 12, 20, QPrinter::Millimeter);
QString html = R"(<!DOCTYPE html>
<html>
<head>
<style>
table {
font-family: arial, sans-serif;
border-collapse: collapse;
width: 100%;
}
td, th {
border: 1px solid #dddddd;
text-align: left;
padding: 8px;
}
tr:nth-child(even) {
background-color: #dddddd;
}
</style>
</head>
<body>
<h2>HTML Table</h2>
<table>
<tr>
<th>Company</th>
<th>Contact</th>
<th>Country</th>
</tr>
<tr>
<td>Alfreds Futterkiste</td>
<td>Maria Anders</td>
<td>Germany</td>
</tr>
<tr>
<td>Centro comercial Moctezuma</td>
<td>Francisco Chang</td>
<td>Mexico</td>
</tr>
<tr>
<td>Ernst Handel</td>
<td>Roland Mendel</td>
<td>Austria</td>
</tr>
<tr>
<td>Island Trading</td>
<td>Helen Bennett</td>
<td>UK</td>
</tr>
<tr>
<td>Laughing Bacchus Winecellars</td>
<td>Yoshi Tannamuri</td>
<td>Canada</td>
</tr>
<tr>
<td>Magazzini Alimentari Riuniti</td>
<td>Giovanni Rovelli</td>
<td>Italy</td>
</tr>
</table>
</body>
</html>
)";
view->setHtml(html);
auto lay = new QVBoxLayout(this);
lay->addWidget(button);
lay->addWidget(progressbar);
lay->addWidget(view);
resize(640, 480);
}
private:
void onLoadFinished(bool ok){
button->setEnabled(ok);
}
void onClicked(){
progressbar->setRange(0, 0);
QString fn = "/Users/s710/Downloads/test.pdf";
printer.setOutputFileName(fn);
view->page()->print(&printer, [this](bool ok){
qDebug() << ok;
progressbar->setRange(0, 1);
});
}
private:
QPushButton *button;
QProgressBar *progressbar;
QWebEngineView *view;
QPrinter printer;
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Widget w;
w.show();
return a.exec();
}
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[英]get HTML from QWebEnginePage in QWebEngineView using Lamda
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