Add run-time qpa offscreen glx support selection

Introduce QT_QPA_OFFSCREEN_NO_GLX to run offscreen qpa
without glx even if compiled with x11 support.

Task-number: QTBUG-63346
Change-Id: I647bf5df27f095c3dd27a90415cc9c445df93fd1
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

src/plugins/platforms/offscreen/offscreen.pro

@@ -21,9 +21,6 @@ qtConfig(system-xcb):qtConfig(xlib):qtConfig(opengl):!qtConfig(opengles2) {
     SOURCES += qoffscreenintegration_x11.cpp
     HEADERS += qoffscreenintegration_x11.h
     QT += glx_support-private
-    system(echo "Using X11 offscreen integration with GLX")
-} else {
-    SOURCES += qoffscreenintegration_dummy.cpp
 }
 
 PLUGIN_TYPE = platforms

src/plugins/platforms/offscreen/qoffscreenintegration.cpp

@@ -66,6 +66,10 @@
 
 #include <qpa/qplatformservices.h>
 
+#if QT_CONFIG(system_xcb) && QT_CONFIG(xlib) && QT_CONFIG(opengl) && !QT_CONFIG(opengles2)
+#include "qoffscreenintegration_x11.h"
+#endif
+
 QT_BEGIN_NAMESPACE
 
 class QCoreTextFontEngine;
@@ -219,4 +223,14 @@ QPlatformServices *QOffscreenIntegration::services() const
     return m_services.data();
 }
 
+QOffscreenIntegration *QOffscreenIntegration::createOffscreenIntegration()
+{
+#if QT_CONFIG(system_xcb) && QT_CONFIG(xlib) && QT_CONFIG(opengl) && !QT_CONFIG(opengles2)
+    QByteArray glx = qgetenv("QT_QPA_OFFSCREEN_NO_GLX");
+    if (glx.isEmpty())
+        return new QOffscreenX11Integration;
+#endif
+    return new QOffscreenIntegration;
+}
+
 QT_END_NAMESPACE

src/plugins/platforms/offscreen/qoffscreenintegration_dummy.cpp

@@ -1,45 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2016 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of the plugins 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.
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#include "qoffscreenintegration.h"
-
-QOffscreenIntegration *QOffscreenIntegration::createOffscreenIntegration()
-{
-    return new QOffscreenIntegration;
-}

src/plugins/platforms/offscreen/qoffscreenintegration_x11.cpp

@@ -77,11 +77,6 @@ private:
     QOffscreenX11Connection *m_connection;
 };
 
-QOffscreenIntegration *QOffscreenIntegration::createOffscreenIntegration()
-{
-    return new QOffscreenX11Integration;
-}
-
 bool QOffscreenX11Integration::hasCapability(QPlatformIntegration::Capability cap) const
 {
     switch (cap) {