Better handling of interrupted PDF printing

- Document the fact Stop WebAction can interrupt the in-progress PDF
generation.

- Update PrintViewManagerQt::PrintPreviewDone(): Normally
IsPrintRenderFrameConnected() implies IsRenderFrameLive(), but we have
to check both to avoid crash when render process exits. (Like Chrome
does.)

- Update PrintViewManagerQt::RequestPrintPreview(): Handle that case when
print preview params were sent between processes at the beginning, but it
was interrupted before RequestPrintPreview() could start PDF generation.

- Add a simple auto test to catch crashes

Task-number: QTBUG-108154
Change-Id: I8a4f9cc97ddcf9a165d66a5981d93a023858fbc1
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
(cherry picked from commit c3ed0e176ccda503c968626010ca36f1f3961fce)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

4 files changed, 27 insertions, 1 deletions

diff --git a/src/core/api/qwebenginepage.cpp b/src/core/api/qwebenginepage.cpp
index ac44fad10..99edc7246 100644
--- a/src/core/api/qwebenginepage.cpp
+++ b/src/core/api/qwebenginepage.cpp
@@ -2248,6 +2248,9 @@ QSizeF QWebEnginePage::contentsSize() const
     To be informed about the result of the request, connect to the signal
     pdfPrintingFinished().
 
+    \note The \l QWebEnginePage::Stop web action can be used to interrupt
+    this asynchronous operation.
+
     If a file already exists at the provided file path, it will be overwritten.
     \sa pdfPrintingFinished()
 */
@@ -2273,6 +2276,8 @@ void QWebEnginePage::printToPdf(const QString &filePath, const QPageLayout &layo
     The \a resultCallback must take a const reference to a QByteArray as parameter. If printing was successful, this byte array
     will contain the PDF data, otherwise, the byte array will be empty.
 
+    \note The \l QWebEnginePage::Stop web action can be used to interrupt this operation.
+
     \warning We guarantee that the callback (\a resultCallback) is always called, but it might be done
     during page destruction. When QWebEnginePage is deleted, the callback is triggered with an invalid
     value and it is not safe to use the corresponding QWebEnginePage or QWebEngineView instance inside it.
diff --git a/src/core/printing/print_view_manager_qt.cpp b/src/core/printing/print_view_manager_qt.cpp
index d8b6f1c1f..7d8a796f7 100644
--- a/src/core/printing/print_view_manager_qt.cpp
+++ b/src/core/printing/print_view_manager_qt.cpp
@@ -277,7 +277,7 @@ void PrintViewManagerQt::resetPdfState()
 
 void PrintViewManagerQt::PrintPreviewDone()
 {
-    if (IsPrintRenderFrameConnected(m_printPreviewRfh))
+    if (m_printPreviewRfh->IsRenderFrameLive() && IsPrintRenderFrameConnected(m_printPreviewRfh))
         GetPrintRenderFrame(m_printPreviewRfh)->OnPrintPreviewDialogClosed();
     m_printPreviewRfh = nullptr;
 }
@@ -338,6 +338,10 @@ void PrintViewManagerQt::ShowScriptedPrintPreview(bool /*source_is_modifiable*/)
 
 void PrintViewManagerQt::RequestPrintPreview(printing::mojom::RequestPrintPreviewParamsPtr /*params*/)
 {
+    if (m_printSettings.empty()) {
+        PrintPreviewDone();
+        return;
+    }
     mojo::AssociatedRemote<printing::mojom::PrintRenderFrame> printRenderFrame;
     m_printPreviewRfh->GetRemoteAssociatedInterfaces()->GetInterface(&printRenderFrame);
     printRenderFrame->PrintPreview(m_printSettings.Clone());
diff --git a/src/webenginewidgets/api/qwebengineview.cpp b/src/webenginewidgets/api/qwebengineview.cpp
index fd74268f2..35fb98138 100644
--- a/src/webenginewidgets/api/qwebengineview.cpp
+++ b/src/webenginewidgets/api/qwebengineview.cpp
@@ -1408,6 +1408,9 @@ void QWebEngineView::printToPdf(const std::function<void(const QByteArray&)> &re
 
     \note Printing runs on the browser process, which is by default not sandboxed.
 
+    \note The data generation step of printing can be interrupted for a short period of time using
+    the \l QWebEnginePage::Stop web action.
+
     \note This function rasterizes the result when rendering onto \a printer. Please consider raising
     the default resolution of \a printer to at least 300 DPI or using printToPdf() to produce
     PDF file output more effectively.
diff --git a/tests/auto/widgets/printing/tst_printing.cpp b/tests/auto/widgets/printing/tst_printing.cpp
index 1c1e0615e..1f9b5059c 100644
--- a/tests/auto/widgets/printing/tst_printing.cpp
+++ b/tests/auto/widgets/printing/tst_printing.cpp
@@ -23,6 +23,7 @@ private slots:
 #if QT_CONFIG(webengine_system_poppler)
     void printToPdfPoppler();
 #endif
+    void interruptPrinting();
 };
 
 void tst_Printing::printToPdfBasic()
@@ -117,6 +118,19 @@ void tst_Printing::printToPdfPoppler()
 }
 #endif
 
+void tst_Printing::interruptPrinting()
+{
+    QWebEngineView view;
+    QSignalSpy spy(&view, &QWebEngineView::loadFinished);
+    view.load(QUrl("qrc:///resources/basic_printing_page.html"));
+    QTRY_VERIFY(spy.size() == 1);
+
+    QTemporaryDir tempDir(QDir::tempPath() + "/tst_qwebengineview-XXXXXX");
+    QVERIFY(tempDir.isValid());
+    view.page()->printToPdf(tempDir.path() + "/file.pdf");
+    // Navigation stop interrupts print job, preferably do this without crash/assert
+    view.page()->triggerAction(QWebEnginePage::Stop);
+}
 
 QTEST_MAIN(tst_Printing)
 #include "tst_printing.moc"