Add proper abstractions to the grid layout engine.

The abstractions are needed so that they can work with both
QGraphicsLayouts and QtQuick.Layouts.

Since the plan is to move the engine to QtGui, this means that the
engine cannot have any references to anything in the QtWidgets module.

As a consequence of that several things had to be done:
* The style info object had to be redone with an abstraction layer
  to get rid of style and widget dependency. (Abstract class is
  called QAbstractLayoutStyleInfo)
* QGridLayoutEngine must be subclassed due to some specializations for
  QGraphicsLayoutItem, manifested as QGraphicsGridLayoutEngine.
* QGridLayoutItem must be subclassed due to some specializations for
  QGraphicsLayoutItem, manifested as QGraphicsGridLayoutEngineItem.

Did also some minor cleanups, reordered arguments so that all styleInfo
arguments are last in all function calls

This also fixes QTBUG-35099 (bug was spotted during this refactoring)

Task-number: QTBUG-35099

Change-Id: If49d40f71870dc8d99d2e145be158e3080b595fa
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>

1 files changed, 108 insertions, 0 deletions

diff --git a/src/widgets/graphicsview/qgraphicslayoutstyleinfo.cpp b/src/widgets/graphicsview/qgraphicslayoutstyleinfo.cpp
new file mode 100644
index 0000000000..3270fc20a3
--- /dev/null
+++ b/src/widgets/graphicsview/qgraphicslayoutstyleinfo.cpp
@@ -0,0 +1,108 @@
+/****************************************************************************
+**
+** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtWidgets 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 Digia.  For licensing terms and
+** conditions see http://qt.digia.com/licensing.  For further information
+** use the contact form at http://qt.digia.com/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 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#include "qgraphicslayoutstyleinfo_p.h"
+#include "qgraphicslayout_p.h"
+#include "qgraphicswidget.h"
+#include <QtWidgets/qstyle.h>
+#include <QtWidgets/qwidget.h>
+#include <QtWidgets/qapplication.h>
+
+QT_BEGIN_NAMESPACE
+
+QGraphicsLayoutStyleInfo::QGraphicsLayoutStyleInfo(const QGraphicsLayoutPrivate *layout)
+    : m_layout(layout), m_style(0)
+{
+    m_widget = new QWidget; // pixelMetric might need a widget ptr
+    if (m_widget)
+        m_styleOption.initFrom(m_widget);
+    m_isWindow = m_styleOption.state & QStyle::State_Window;
+}
+
+QGraphicsLayoutStyleInfo::~QGraphicsLayoutStyleInfo()
+{
+    delete m_widget;
+}
+
+qreal QGraphicsLayoutStyleInfo::combinedLayoutSpacing(QLayoutPolicy::ControlTypes controls1,
+                                                      QLayoutPolicy::ControlTypes controls2,
+                                                      Qt::Orientation orientation) const
+{
+    Q_ASSERT(style());
+    return style()->combinedLayoutSpacing(QSizePolicy::ControlTypes(int(controls1)), QSizePolicy::ControlTypes(int(controls2)),
+                                          orientation, const_cast<QStyleOption*>(&m_styleOption), widget());
+}
+
+qreal QGraphicsLayoutStyleInfo::perItemSpacing(QLayoutPolicy::ControlType control1,
+                                               QLayoutPolicy::ControlType control2,
+                                               Qt::Orientation orientation) const
+{
+    Q_ASSERT(style());
+    return style()->layoutSpacing(QSizePolicy::ControlType(control1), QSizePolicy::ControlType(control2),
+                                  orientation, const_cast<QStyleOption*>(&m_styleOption), widget());
+}
+
+qreal QGraphicsLayoutStyleInfo::spacing(Qt::Orientation orientation) const
+{
+    Q_ASSERT(style());
+    return style()->pixelMetric(orientation == Qt::Horizontal ? QStyle::PM_LayoutHorizontalSpacing : QStyle::PM_LayoutVerticalSpacing);
+}
+
+qreal QGraphicsLayoutStyleInfo::windowMargin(Qt::Orientation orientation) const
+{
+    return style()->pixelMetric(orientation == Qt::Vertical
+                                ? QStyle::PM_LayoutBottomMargin
+                                : QStyle::PM_LayoutRightMargin,
+                                const_cast<QStyleOption*>(&m_styleOption), widget());
+}
+
+QWidget *QGraphicsLayoutStyleInfo::widget() const { return m_widget; }
+
+QStyle *QGraphicsLayoutStyleInfo::style() const
+{
+    if (!m_style) {
+        Q_ASSERT(m_layout);
+        QGraphicsItem *item = m_layout->parentItem();
+        m_style = (item && item->isWidget()) ? static_cast<QGraphicsWidget*>(item)->style() : QApplication::style();
+    }
+    return m_style;
+}
+
+QT_END_NAMESPACE