Fix printing from PDF plugin

Update the plugin finder logic everywhere to match with Chrome. This
comes with a small cleanup: collect PDF-related helper functions
scattered around WebEngine in one pdf_util_qt implementation.

Add auto test to catch this recurring issue earlier.

Task-number: QTBUG-119878
Change-Id: I03b2bd62bebf5b38afc572e0629db106d024e89d
Reviewed-by: Michael Brüning <michael.bruning@qt.io>
(cherry picked from commit e09cf6e7a1f582d06f86ff2c166b7c2269fd4b47)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit a1ffdacd23c13d97793b87f098e3ec7ab8ff1de6)
Reviewed-by: Peter Varga <pvarga@inf.u-szeged.hu>

9 files changed, 193 insertions, 58 deletions

diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 75a41d6a6..c4e413351 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -152,6 +152,7 @@ foreach(arch ${archs})
                 ozone/platform_window_qt.cpp ozone/platform_window_qt.h
                 ozone/surface_factory_qt.cpp ozone/surface_factory_qt.h
                 permission_manager_qt.cpp permission_manager_qt.h
+                pdf_util_qt.cpp pdf_util_qt.h
                 platform_notification_service_qt.cpp platform_notification_service_qt.h
                 pointer_device_qt.cpp
                 pref_service_adapter.cpp pref_service_adapter.h
diff --git a/src/core/extensions/pdf_iframe_navigation_throttle_qt.cpp b/src/core/extensions/pdf_iframe_navigation_throttle_qt.cpp
index 9b6b38a52..9a2feb816 100644
--- a/src/core/extensions/pdf_iframe_navigation_throttle_qt.cpp
+++ b/src/core/extensions/pdf_iframe_navigation_throttle_qt.cpp
@@ -26,12 +26,12 @@
 #include "ui/base/webui/jstemplate_builder.h"
 #include "ui/base/webui/web_ui_util.h"
 
+#include "pdf_util_qt.h"
+
 #include <QtGlobal>
 
 namespace extensions {
 
-constexpr char kPDFMimeType[] = "application/pdf";
-
 // Used to scope the posted navigation task to the lifetime of |web_contents|.
 class PdfWebContentsLifetimeHelper : public content::WebContentsUserData<PdfWebContentsLifetimeHelper>
 {
@@ -76,7 +76,7 @@ bool IsPDFPluginEnabled(content::NavigationHandle *navigation_handle, bool *is_s
                 process_id, routing_id,
                 navigation_handle->GetWebContents()->GetBrowserContext(),
                 navigation_handle->GetURL(),
-                kPDFMimeType, false /* allow_wildcard */,
+                QtWebEngineCore::kPDFMimeType, false /* allow_wildcard */,
                 is_stale, &plugin_info, nullptr /* actual_mime_type */);
 }
 
@@ -119,7 +119,7 @@ content::NavigationThrottle::ThrottleCheckResult PDFIFrameNavigationThrottleQt::
 
     std::string mime_type;
     response_headers->GetMimeType(&mime_type);
-    if (mime_type != kPDFMimeType)
+    if (mime_type != QtWebEngineCore::kPDFMimeType)
         return content::NavigationThrottle::PROCEED;
 
     // We MUST download responses marked as attachments rather than showing
diff --git a/src/core/pdf_util_qt.cpp b/src/core/pdf_util_qt.cpp
new file mode 100644
index 000000000..9503f5910
--- /dev/null
+++ b/src/core/pdf_util_qt.cpp
@@ -0,0 +1,92 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE.Chromium file.
+
+#include "pdf_util_qt.h"
+
+#include <QtGlobal>
+
+#include "base/check.h"
+#include "chrome/common/webui_url_constants.h"
+#include "content/public/browser/render_frame_host.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/browser/web_contents.h"
+#include "extensions/buildflags/buildflags.h"
+#include "url/gurl.h"
+#include "url/origin.h"
+
+#if BUILDFLAG(ENABLE_EXTENSIONS)
+#include "extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h"
+#include "extensions/common/constants.h"
+#endif  // BUILDFLAG(ENABLE_EXTENSIONS)
+
+namespace QtWebEngineCore {
+
+bool IsPdfExtensionOrigin(const url::Origin &origin)
+{
+#if BUILDFLAG(ENABLE_EXTENSIONS)
+    return origin.scheme() == extensions::kExtensionScheme
+        && origin.host() == extension_misc::kPdfExtensionId;
+#else
+    Q_UNUSED(origin);
+    return false;
+#endif
+}
+
+bool IsPdfInternalPluginAllowedOrigin(const url::Origin &origin)
+{
+    if (IsPdfExtensionOrigin(origin))
+        return true;
+
+    // Allow embedding the internal PDF plugin in chrome://print.
+    if (origin == url::Origin::Create(GURL(chrome::kChromeUIPrintURL)))
+        return true;
+
+    // Only allow the PDF plugin in the known, trustworthy origins that are
+    // allowlisted above.  See also https://crbug.com/520422 and
+    // https://crbug.com/1027173.
+    return false;
+}
+
+content::RenderFrameHost *GetFullPagePlugin(content::WebContents *contents)
+{
+    content::RenderFrameHost *full_page_plugin = nullptr;
+#if BUILDFLAG(ENABLE_EXTENSIONS)
+    contents->ForEachRenderFrameHostWithAction([&full_page_plugin](content::RenderFrameHost *rfh) {
+        auto* guest_view = extensions::MimeHandlerViewGuest::FromRenderFrameHost(rfh);
+        if (guest_view && guest_view->is_full_page_plugin()) {
+            DCHECK_EQ(guest_view->GetGuestMainFrame(), rfh);
+            full_page_plugin = rfh;
+            return content::RenderFrameHost::FrameIterationAction::kStop;
+        }
+        return content::RenderFrameHost::FrameIterationAction::kContinue;
+    });
+#endif  // BUILDFLAG(ENABLE_EXTENSIONS)
+    return full_page_plugin;
+}
+
+content::RenderFrameHost *FindPdfChildFrame(content::RenderFrameHost *rfh)
+{
+    if (!rfh)
+        return nullptr;
+
+    if (!IsPdfExtensionOrigin(rfh->GetLastCommittedOrigin()))
+        return nullptr;
+
+    content::RenderFrameHost *pdf_rfh = nullptr;
+    rfh->ForEachRenderFrameHost([&pdf_rfh](content::RenderFrameHost *rfh) {
+        if (!rfh->GetProcess()->IsPdf())
+            return;
+
+        DCHECK(IsPdfExtensionOrigin(rfh->GetParent()->GetLastCommittedOrigin()));
+        DCHECK(!pdf_rfh);
+        pdf_rfh = rfh;
+    });
+
+    return pdf_rfh;
+}
+
+} // namespace QtWebEngineCore
diff --git a/src/core/pdf_util_qt.h b/src/core/pdf_util_qt.h
new file mode 100644
index 000000000..5ee211800
--- /dev/null
+++ b/src/core/pdf_util_qt.h
@@ -0,0 +1,34 @@
+// Copyright (C) 2023 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+// Copyright 2021 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE.Chromium file.
+
+#ifndef PDF_UTIL_QT_H
+#define PDF_UTIL_QT_H
+
+namespace content {
+class RenderFrameHost;
+class WebContents;
+}  // namespace content
+
+namespace url {
+class Origin;
+}  // namespace url
+
+namespace QtWebEngineCore {
+
+// from chrome/common/pdf_util.cc:
+constexpr char kPDFMimeType[] = "application/pdf";
+
+bool IsPdfExtensionOrigin(const url::Origin &origin);
+bool IsPdfInternalPluginAllowedOrigin(const url::Origin &origin);
+
+// from chrome/browser/pdf/pdf_frame_util.cc:
+content::RenderFrameHost *GetFullPagePlugin(content::WebContents *contents);
+content::RenderFrameHost *FindPdfChildFrame(content::RenderFrameHost *rfh);
+
+} // namespace QtWebEngineCore
+
+#endif // PDF_UTIL_QT_H
diff --git a/src/core/printing/pdf_web_contents_helper_client_qt.cpp b/src/core/printing/pdf_web_contents_helper_client_qt.cpp
index 4deb398c6..0ff7499c3 100644
--- a/src/core/printing/pdf_web_contents_helper_client_qt.cpp
+++ b/src/core/printing/pdf_web_contents_helper_client_qt.cpp
@@ -9,33 +9,7 @@
 #include "extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h"
 #include "extensions/common/constants.h"
 
-namespace {
-bool IsPdfExtensionOrigin(const url::Origin &origin)
-{
-    return origin.scheme() == extensions::kExtensionScheme &&
-           origin.host() == extension_misc::kPdfExtensionId;
-}
-
-// from chrome/browser/pdf/pdf_frame_util.cc:
-content::RenderFrameHost *FindPdfChildFrame(content::RenderFrameHost *rfh)
-{
-    if (!IsPdfExtensionOrigin(rfh->GetLastCommittedOrigin()))
-        return nullptr;
-
-    content::RenderFrameHost *pdf_rfh = nullptr;
-    rfh->ForEachRenderFrameHost(
-                    [&pdf_rfh](content::RenderFrameHost *rfh) {
-                        if (!rfh->GetProcess()->IsPdf())
-                            return;
-
-                        DCHECK(IsPdfExtensionOrigin(rfh->GetParent()->GetLastCommittedOrigin()));
-                        DCHECK(!pdf_rfh);
-                        pdf_rfh = rfh;
-                    });
-
-    return pdf_rfh;
-}
-}  // namespace
+#include "pdf_util_qt.h"
 
 PDFWebContentsHelperClientQt::PDFWebContentsHelperClientQt() = default;
 PDFWebContentsHelperClientQt::~PDFWebContentsHelperClientQt() = default;
@@ -43,7 +17,7 @@ PDFWebContentsHelperClientQt::~PDFWebContentsHelperClientQt() = default;
 content::RenderFrameHost *PDFWebContentsHelperClientQt::FindPdfFrame(content::WebContents *contents)
 {
     content::RenderFrameHost *main_frame = contents->GetPrimaryMainFrame();
-    content::RenderFrameHost *pdf_frame = FindPdfChildFrame(main_frame);
+    content::RenderFrameHost *pdf_frame = QtWebEngineCore::FindPdfChildFrame(main_frame);
     return pdf_frame ? pdf_frame : main_frame;
 }
 
diff --git a/src/core/printing/print_view_manager_qt.cpp b/src/core/printing/print_view_manager_qt.cpp
index 892c9e406..060417e5b 100644
--- a/src/core/printing/print_view_manager_qt.cpp
+++ b/src/core/printing/print_view_manager_qt.cpp
@@ -8,6 +8,7 @@
 
 #include "print_view_manager_qt.h"
 
+#include "pdf_util_qt.h"
 #include "type_conversion.h"
 #include "web_contents_adapter_client.h"
 #include "web_contents_view_qt.h"
@@ -238,7 +239,11 @@ bool PrintViewManagerQt::PrintToPDFInternal(const QPageLayout &pageLayout,
     if (web_contents()->IsCrashed())
         return false;
 
-    content::RenderFrameHost* rfh = web_contents()->GetPrimaryMainFrame();
+    content::RenderFrameHost *rfh = web_contents()->GetPrimaryMainFrame();
+    // Use the plugin frame for printing if web_contents() is a PDF viewer guest
+    content::RenderFrameHost *full_page_plugin = GetFullPagePlugin(web_contents());
+    if (content::RenderFrameHost *pdf_rfh = FindPdfChildFrame(full_page_plugin ? full_page_plugin : rfh))
+        rfh = pdf_rfh;
     GetPrintRenderFrame(rfh)->InitiatePrintPreview(mojo::PendingAssociatedRemote<printing::mojom::PrintRenderer>(), false);
 
     DCHECK(!m_printPreviewRfh);
diff --git a/src/core/renderer/print_web_view_helper_delegate_qt.cpp b/src/core/renderer/print_web_view_helper_delegate_qt.cpp
index f77b6fbbc..f01568e65 100644
--- a/src/core/renderer/print_web_view_helper_delegate_qt.cpp
+++ b/src/core/renderer/print_web_view_helper_delegate_qt.cpp
@@ -15,8 +15,10 @@
 #include "chrome/common/webui_url_constants.h"
 #include "extensions/common/constants.h"
 #include "third_party/blink/public/web/web_document.h"
+#include "extensions/renderer/guest_view/mime_handler_view/post_message_support.h"
 #endif  // BUILDFLAG(ENABLE_EXTENSIONS)
 
+#include "pdf_util_qt.h"
 #include "print_web_view_helper_delegate_qt.h"
 #include "web_engine_library_info.h"
 
@@ -24,33 +26,13 @@ namespace QtWebEngineCore {
 
 PrintWebViewHelperDelegateQt::~PrintWebViewHelperDelegateQt() {}
 
-bool IsPdfExtensionOrigin(const url::Origin& origin)
-{
-#if BUILDFLAG(ENABLE_EXTENSIONS)
-    return origin.scheme() == extensions::kExtensionScheme
-        && origin.host() == extension_misc::kPdfExtensionId;
-#else
-    Q_UNUSED(origin);
-    return false;
-#endif
-}
-
 blink::WebElement PrintWebViewHelperDelegateQt::GetPdfElement(blink::WebLocalFrame *frame)
 {
 #if BUILDFLAG(ENABLE_EXTENSIONS)
-    const url::Origin origin = frame->GetDocument().GetSecurityOrigin();
-    bool inside_print_preview = origin == url::Origin::Create(GURL(chrome::kChromeUIPrintURL));
-    bool inside_pdf_extension = IsPdfExtensionOrigin(origin);
-    if (inside_print_preview || inside_pdf_extension) {
-        // <object> with id="plugin" is created in
-        // chrome/browser/resources/pdf/pdf_viewer_base.js.
-        auto viewer_element = frame->GetDocument().GetElementById("viewer");
-        if (!viewer_element.IsNull() && !viewer_element.ShadowRoot().IsNull()) {
-            auto plugin_element = viewer_element.ShadowRoot().QuerySelector("#plugin");
-            if (!plugin_element.IsNull())
-                return plugin_element;
-        }
-        NOTREACHED();
+    if (frame->Parent() && IsPdfInternalPluginAllowedOrigin(frame->Parent()->GetSecurityOrigin())) {
+        auto plugin_element = frame->GetDocument().QuerySelector("embed");
+        DCHECK(!plugin_element.IsNull());
+        return plugin_element;
     }
 #endif  // BUILDFLAG(ENABLE_EXTENSIONS)
     return blink::WebElement();
diff --git a/src/core/web_contents_adapter.cpp b/src/core/web_contents_adapter.cpp
index fe30206ce..f44675171 100644
--- a/src/core/web_contents_adapter.cpp
+++ b/src/core/web_contents_adapter.cpp
@@ -15,6 +15,7 @@
 #include "favicon_service_factory_qt.h"
 #include "find_text_helper.h"
 #include "media_capture_devices_dispatcher.h"
+#include "pdf_util_qt.h"
 #include "profile_adapter.h"
 #include "profile_qt.h"
 #include "qwebengineloadinginfo.h"
@@ -1974,7 +1975,7 @@ WebContentsAdapter::LifecycleState WebContentsAdapter::determineRecommendedState
     // Do not discard PDFs as they might contain entry that is not saved and they
     // don't remember their scrolling positions. See crbug.com/547286 and
     // crbug.com/65244.
-    if (m_webContents->GetContentsMimeType() == "application/pdf")
+    if (m_webContents->GetContentsMimeType() == kPDFMimeType)
         return LifecycleState::Frozen;
 
     return LifecycleState::Discarded;
diff --git a/tests/auto/widgets/printing/tst_printing.cpp b/tests/auto/widgets/printing/tst_printing.cpp
index 1f9b5059c..605fb57b5 100644
--- a/tests/auto/widgets/printing/tst_printing.cpp
+++ b/tests/auto/widgets/printing/tst_printing.cpp
@@ -3,6 +3,7 @@
 
 #include <QtWebEngineCore/private/qtwebenginecoreglobal_p.h>
 #include <QtWebEngineCore/qtwebenginecore-config.h>
+#include <QWebEngineSettings>
 #include <QWebEngineView>
 #include <QTemporaryDir>
 #include <QTest>
@@ -22,6 +23,7 @@ private slots:
     void printRequest();
 #if QT_CONFIG(webengine_system_poppler)
     void printToPdfPoppler();
+    void printFromPdfViewer();
 #endif
     void interruptPrinting();
 };
@@ -116,6 +118,50 @@ void tst_Printing::printToPdfPoppler()
     QVERIFY2(pdfPage->search(ustring::from_latin1("Hello Paper World"), rect, page::search_from_top,
                      case_sensitive ), "Could not find text");
 }
+
+void tst_Printing::printFromPdfViewer()
+{
+    using namespace poppler;
+
+    QWebEngineView view;
+    view.page()->settings()->setAttribute(QWebEngineSettings::PluginsEnabled, true);
+    view.page()->settings()->setAttribute(QWebEngineSettings::PdfViewerEnabled, true);
+
+    // Load a basic HTML
+    QSignalSpy spy(&view, &QWebEngineView::loadFinished);
+    view.load(QUrl("qrc:///resources/basic_printing_page.html"));
+    QTRY_COMPARE(spy.size(), 1);
+
+    // Create a PDF
+    QTemporaryDir tempDir(QDir::tempPath() + "/tst_printing-XXXXXX");
+    QVERIFY(tempDir.isValid());
+    QString path = tempDir.path() + "/basic_page.pdf";
+    QSignalSpy savePdfSpy(view.page(), &QWebEnginePage::pdfPrintingFinished);
+    view.page()->printToPdf(path);
+    QTRY_COMPARE(savePdfSpy.size(), 1);
+
+    // Open the new file with the PDF viewer plugin
+    view.load(QUrl("file://" + path));
+    QTRY_COMPARE(spy.size(), 2);
+
+    // Print from the plugin
+    // loadFinished signal is not reliable when loading a PDF file, because it has multiple phases.
+    // Workaround: Try to print it a couple of times until the result matches the expected.
+    CallbackSpy<QByteArray> resultSpy;
+    bool ok = QTest::qWaitFor([&]() -> bool {
+        view.printToPdf(resultSpy.ref());
+        QByteArray data = resultSpy.waitForResult();
+
+        // Check if the result contains text from the original basic HTML
+        // This catches all the typical issues: empty result or printing the WebUI without PDF content.
+        QScopedPointer<document> pdf(document::load_from_raw_data(data.constData(), data.length()));
+        QScopedPointer<page> pdfPage(pdf->create_page(0));
+        rectf rect;
+        return pdfPage->search(ustring::from_latin1("Hello Paper World"), rect, page::search_from_top,
+                            case_sensitive);
+    }, 10000);
+    QVERIFY(ok);
+}
 #endif
 
 void tst_Printing::interruptPrinting()