qt_demoe/designer/lib/shared/qdesigner_widgetitem_p.h

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//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists for the convenience
// of Qt Designer.  This header
// file may change from version to version without notice, or even be removed.
//
// We mean it.
//

#ifndef DESIGNERWIDGETITEM_H
#define DESIGNERWIDGETITEM_H

#include "shared_global_p.h"

#include <QtGui/QLayoutItem>
#include <QtCore/QObject>

QT_BEGIN_NAMESPACE

class QDesignerFormEditorInterface;

namespace qdesigner_internal {

// QDesignerWidgetItem: A Layout Item that is used for non-containerextension-
// containers (QFrame, etc) on Designer forms. It prevents its widget
// from being slammed to size 0 if the widget has no layout:
// Pre 4.5, this item ensured only that QWidgets and QFrames were not squeezed
// to size 0 since they have an invalid size hint when non-laid out.
// Since 4.5, the item is used for every  non-containerextension-container.
// In case the container has itself a layout, it merely tracks the minimum
// size. If the container has no layout and is not subject to some stretch
// factor, it will return the last valid size. The effect is that after
// breaking a layout on a container within a layout, it just maintains its
// last size and is not slammed to 0,0. In addition, it can be resized.
// The class keeps track of the containing layout by tracking widget reparent
// and destroyed slots as Designer will for example re-create grid layouts to
// shrink them.

class QDESIGNER_SHARED_EXPORT QDesignerWidgetItem : public QObject, public QWidgetItemV2  {
    Q_DISABLE_COPY(QDesignerWidgetItem)
    Q_OBJECT
public:
    explicit QDesignerWidgetItem(const QLayout *containingLayout, QWidget *w, Qt::Orientations o = Qt::Horizontal|Qt::Vertical);

    const QLayout *containingLayout() const;

    inline QWidget *constWidget() const { return const_cast<QDesignerWidgetItem*>(this)->widget(); }

    virtual QSize minimumSize() const;
    virtual QSize sizeHint()    const;

    // Resize: Takes effect if the contained widget does not have a layout
    QSize nonLaidOutMinSize() const;
    void setNonLaidOutMinSize(const QSize &s);

    QSize nonLaidOutSizeHint() const;
    void setNonLaidOutSizeHint(const QSize &s);

    // Check whether a QDesignerWidgetItem should be installed
    static bool check(const QLayout *layout, QWidget *w, Qt::Orientations *ptrToOrientations = 0);

    // Register itself using QLayoutPrivate's widget item factory method hook
    static void install();
    static void deinstall();

    // Check for a non-container extension container
    static bool isContainer(const QDesignerFormEditorInterface *core, QWidget *w);

    static bool subjectToStretch(const QLayout *layout, QWidget *w);

    virtual bool eventFilter(QObject * watched, QEvent * event);

private slots:
    void layoutChanged();

private:
    void expand(QSize *s) const;
    bool subjectToStretch() const;

    const Qt::Orientations m_orientations;
    mutable QSize m_nonLaidOutMinSize;
    mutable QSize m_nonLaidOutSizeHint;
    mutable const QLayout *m_cachedContainingLayout;
};

// Helper class that ensures QDesignerWidgetItem is installed while an
// instance is in scope.

class QDESIGNER_SHARED_EXPORT QDesignerWidgetItemInstaller {
    Q_DISABLE_COPY(QDesignerWidgetItemInstaller)

public:
    QDesignerWidgetItemInstaller();
    ~QDesignerWidgetItemInstaller();

private:
    static int m_instanceCount;
};

} // namespace qdesigner_internal

QT_END_NAMESPACE

#endif