Changeset 561 for trunk/doc/src/examples/basicgraphicslayouts.qdoc

Timestamp:

Feb 11, 2010, 11:19:06 PM (15 years ago)

Author:

Dmitry A. Kuminov

Message:

trunk: Merged in qt 4.6.1 sources.

Location:

trunk

Files:

• . (modified) (1 prop)
• doc/src/examples/basicgraphicslayouts.qdoc (modified) (6 diffs)

trunk/doc/src/examples/basicgraphicslayouts.qdoc

@@ -2 +2 @@
 **
 ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
-** Contact: Qt Software Information (qt-info@nokia.com)
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
 **
 ** This file is part of the documentation of the Qt Toolkit.
@@ -21 +22 @@
 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
 **
-** In addition, as a special exception, Nokia gives you certain
-** additional rights. These rights are described in the Nokia Qt LGPL
-** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
-** package.
+** In addition, as a special exception, Nokia gives you certain additional
+** rights.  These rights are described in the Nokia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
 **
 ** GNU General Public License Usage
@@ -34 +34 @@
 ** met: http://www.gnu.org/copyleft/gpl.html.
 **
-** If you are unsure which license is appropriate for your use, please
-** contact the sales department at qt-sales@nokia.com.
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
 ** $QT_END_LICENSE$
 **
@@ -46 +46 @@
     The Basic Graphics Layouts example shows how to use the layout classes
     in QGraphicsView: QGraphicsLinearLayout and QGraphicsGridLayout.
+    In addition to that it shows how to write your own custom layout item.
 
     \image basicgraphicslayouts-example.png Screenshot of the Basic Layouts Example
@@ -116 +117 @@
     \section1 LayoutItem Class Definition
 
-    The \c LayoutItem class is a subclass of QGraphicsWidget. It has a
-    constructor, a destructor, and a reimplementation of the
-    {QGraphicsItem::paint()}{paint()} function.
+    The \c LayoutItem class is a subclass of QGraphicsLayoutItem and
+    QGraphicsItem. It has a constructor, a destructor, and some required
+    reimplementations.
+    Since it inherits QGraphicsLayoutItem it must reimplement
+    {QGraphicsLayoutItem::setGeometry()}{setGeometry()} and
+    {QGraphicsLayoutItem::sizeHint()}{sizeHint()}.
+    In addition to that it inherits QGraphicsItem, so it must reimplement
+    {QGraphicsItem::boundingRect()}{boundingRect()} and
+    {QGraphicsItem::paint()}{paint()}.
 
     \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.h 0
 
-    The \c LayoutItem class also has a private instance of QPixmap, \c pix.
-
-    \note We subclass QGraphicsWidget so that \c LayoutItem objects can
-    be automatically plugged into a layout, as QGraphicsWidget is a
-    specialization of QGraphicsLayoutItem.
+    The \c LayoutItem class also has a private instance of QPixmap, \c m_pix.
 
     \section1 LayoutItem Class Implementation
 
-    In \c{LayoutItem}'s constructor, \c pix is instantiated and the
-    \c{QT_original_R.png} image is loaded into it. We set the size of
-    \c LayoutItem to be slightly larger than the size of the pixmap as we
-    require some space around it for borders that we will paint later.
-    Alternatively, you could scale the pixmap to prevent the item from
-    becoming smaller than the pixmap.
+    In \c{LayoutItem}'s constructor, \c m_pix is instantiated and the
+    \c{block.png} image is loaded into it.
 
     \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.cpp 0
@@ -149 +148 @@
     \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.cpp 2
 
+    The reimplementation of {QGraphicsItem::boundingRect()}{boundingRect()}
+    will set the top left corner at (0,0), and the size of it will be
+    the size of the layout items
+    {QGraphicsLayoutItem::geometry()}{geometry()}. This is the area that
+    we paint within.
+
+    \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.cpp 3
+
+
+    The reimplementation of {QGraphicsLayoutItem::setGeometry()}{setGeometry()}
+    simply calls its baseclass implementation. However, since this will change
+    the boundingRect we must also call
+    {QGraphicsItem::prepareGeometryChange()}{prepareGeometryChange()}.
+    Finally, we move the item according to \c geom.topLeft().
+
+    \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.cpp 4
+
+
+    Since we don't want the size of the item to be smaller than the pixmap, we
+    must make sure that we return a size hint that is larger than \c m_pix.
+    We also add some extra space around for borders that we will paint later.
+    Alternatively, you could scale the pixmap to prevent the item from
+    becoming smaller than the pixmap.
+    The preferred size is the same as the minimum size hint, while we set
+    maximum to be a large value
+
+    \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.cpp 5
+
 */