Add widgets API for printing on a QPrinter

Renders the content to a PDF document and then renders this on a
QPrinter-backed QPainter using the PDFium library.

PDFium bitmap to QImage conversion based on work by Paulo Pinheiro
<paulvap.os@gmail.com>.

[ChangeLog][QtWebEngineWidgets][Printing] Enables printing QWebPage
content on a QPrinter. Currently does not support previewing the
document. Widgets only for the moment.

Change-Id: I9a5264433093379aee90f5e4f69bf2aee8814f2b
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

3 files changed, 43 insertions, 0 deletions

diff --git a/src/webenginewidgets/api/qwebenginepage.cpp b/src/webenginewidgets/api/qwebenginepage.cpp
index c180699f3..428cccd9a 100644
--- a/src/webenginewidgets/api/qwebenginepage.cpp
+++ b/src/webenginewidgets/api/qwebenginepage.cpp
@@ -373,6 +373,13 @@ void QWebEnginePagePrivate::didPrintPage(quint64 requestId, const QByteArray &re
     m_callbacks.invoke(requestId, result);
 }
 
+#ifndef QT_NO_PRINTER
+void QWebEnginePagePrivate::didPrintPageOnPrinter(quint64 requestId, bool result)
+{
+    m_callbacks.invoke(requestId, result);
+}
+#endif
+
 void QWebEnginePagePrivate::passOnFocus(bool reverse)
 {
     if (view)
@@ -1841,6 +1848,28 @@ void QWebEnginePage::printToPdf(const QWebEngineCallback<const QByteArray&> &res
     d->m_callbacks.registerCallback(requestId, resultCallback);
 }
 
+#ifndef QT_NO_PRINTER
+/*!
+    \fn void QWebEnginePage::print(const QPrinter &printer, FunctorOrLambda resultCallback)
+    Renders the current content of the page into a temporary PDF document, then prints it using \a printer.
+
+    The settings for creating and printing the PDF document will be retrieved from the \a printer
+    object.
+    It is the users responsibility to ensure the \a printer remains valid until \a resultCallback
+    has been called.
+
+    The \a resultCallback must take a boolean as parameter. If printing was successful, this
+    boolean will have the value \c true, otherwise, its value will be \c false.
+    \since 5.8
+*/
+void QWebEnginePage::print(QPrinter *printer, const QWebEngineCallback<bool> &resultCallback)
+{
+    Q_D(QWebEnginePage);
+    quint64 requestId = d->adapter->printOnPrinterCallbackResult(printer);
+    d->m_callbacks.registerCallback(requestId, resultCallback);
+}
+#endif // QT_NO_PRINTER
+
 /*!
     \since 5.7
 
diff --git a/src/webenginewidgets/api/qwebenginepage.h b/src/webenginewidgets/api/qwebenginepage.h
index bb46cd9fb..923c3bb70 100644
--- a/src/webenginewidgets/api/qwebenginepage.h
+++ b/src/webenginewidgets/api/qwebenginepage.h
@@ -54,6 +54,9 @@
 
 QT_BEGIN_NAMESPACE
 class QMenu;
+#ifndef QT_NO_PRINTER
+class QPrinter;
+#endif
 class QWebChannel;
 class QWebEngineContextMenuData;
 class QWebEngineFullScreenRequest;
@@ -280,6 +283,14 @@ public:
     void printToPdf(const QWebEngineCallback<const QByteArray&> &resultCallback, const QPageLayout &layout = QPageLayout(QPageSize(QPageSize::A4), QPageLayout::Portrait, QMarginsF()));
 #endif
 
+#ifndef QT_NO_PRINTER
+#ifdef Q_QDOC
+    void print(QPrinter *printer, FunctorOrLambda resultCallback)
+#else
+    void print(QPrinter *printer, const QWebEngineCallback<bool> &resultCallback);
+#endif // QDOC
+#endif // QT_NO_PRINTER
+
     const QWebEngineContextMenuData &contextMenuData() const;
     void viewSource();
     bool canViewSource() const;
diff --git a/src/webenginewidgets/api/qwebenginepage_p.h b/src/webenginewidgets/api/qwebenginepage_p.h
index 8d2a86350..93ebdf6e6 100644
--- a/src/webenginewidgets/api/qwebenginepage_p.h
+++ b/src/webenginewidgets/api/qwebenginepage_p.h
@@ -119,6 +119,9 @@ public:
     virtual void didFetchDocumentInnerText(quint64 requestId, const QString& result) Q_DECL_OVERRIDE;
     virtual void didFindText(quint64 requestId, int matchCount) Q_DECL_OVERRIDE;
     virtual void didPrintPage(quint64 requestId, const QByteArray &result) Q_DECL_OVERRIDE;
+#ifndef QT_NO_PRINTER
+    virtual void didPrintPageOnPrinter(quint64 requestId, bool result) Q_DECL_OVERRIDE;
+#endif
     virtual void passOnFocus(bool reverse) Q_DECL_OVERRIDE;
     virtual void javaScriptConsoleMessage(JavaScriptConsoleMessageLevel level, const QString& message, int lineNumber, const QString& sourceID) Q_DECL_OVERRIDE;
     virtual void authenticationRequired(QSharedPointer<QtWebEngineCore::AuthenticationDialogController>) Q_DECL_OVERRIDE;