Doc: Fix documentation build to work with Clang-enabled QDoc

Since Qt 5.11, QDoc uses Clang to parse C++ code for documentation.

As we have a combined documentation project under src/webengine that
covers also webenginewidgets, qmake does not pass the full set
of include paths required for Clang to parse also webenginewidgets
documentation. Fix this by adding the required include paths in
qtwebengine.qdocconf, and by using a custom module header, used
for doc builds, to pull in also the QtWebEngineWidgets module
header which Clang needs.

Task-number: QTBUG-66398
Change-Id: I1da547745c0c06762be216ae55724508b5d6a700
Reviewed-by: Jüri Valdmann <juri.valdmann@qt.io>
Reviewed-by: Kai Koehne <kai.koehne@qt.io>

2 files changed, 51 insertions, 0 deletions

diff --git a/src/webengine/QtWebEngine_pch.h b/src/webengine/QtWebEngine_pch.h
new file mode 100644
index 000000000..ef20376dc
--- /dev/null
+++ b/src/webengine/QtWebEngine_pch.h
@@ -0,0 +1,44 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtWebEngine module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+// Module header file used for documentation builds only.
+#ifdef Q_CLANG_QDOC
+#include <QtWebEngine>
+#include <QtWebEngineWidgets>
+#endif // Q_CLANG_QDOC
diff --git a/src/webengine/doc/qtwebengine.qdocconf b/src/webengine/doc/qtwebengine.qdocconf
index 7b1bad4e6..401e59f31 100644
--- a/src/webengine/doc/qtwebengine.qdocconf
+++ b/src/webengine/doc/qtwebengine.qdocconf
@@ -38,6 +38,13 @@ manifestmeta.highlighted.names += "QtWebEngine/WebEngine Widgets Simple Browser
 
 tagfile                 = ../../../doc/qtwebengine/qtwebengine.tags
 
+# Custom module header for clang that pulls in also QtWebEngineWidgets
+moduleheader = QtWebEngine_pch.h
+
+# Additional include paths for clang
+includepaths = -I $QT_PLUGIN_PATH/../include/QtWidgets \
+               -I $QT_PLUGIN_PATH/../include/QtWebEngineWidgets
+
 depends += qtcore \
            qtgui \
            qtlocation \