806dda08d6
Updated those .qdoc files to refer to the new relative examples emplacement. Images and snippets to be moved later. Also grouped all widgets related examples under widgets. Change-Id: Ib29696e2d8948524537f53e8dda88f9ee26a597f Reviewed-by: J-P Nurmi <j-p.nurmi@nokia.com>
165 lines
6.5 KiB
Plaintext
165 lines
6.5 KiB
Plaintext
/****************************************************************************
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**
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** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
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** Contact: http://www.qt-project.org/
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**
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** This file is part of the documentation of the Qt Toolkit.
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**
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** $QT_BEGIN_LICENSE:FDL$
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** GNU Free Documentation License
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** Alternatively, this file may be used under the terms of the GNU Free
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** Documentation License version 1.3 as published by the Free Software
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** Foundation and appearing in the file included in the packaging of
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** this file.
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**
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** Other Usage
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** Alternatively, this file may be used in accordance with the terms
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** and conditions contained in a signed written agreement between you
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** and Nokia.
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**
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**
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**
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**
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**
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** $QT_END_LICENSE$
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**
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****************************************************************************/
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/*!
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\example graphicsview/basicgraphicslayouts
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\title Basic Graphics Layouts Example
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The Basic Graphics Layouts example shows how to use the layout classes
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in QGraphicsView: QGraphicsLinearLayout and QGraphicsGridLayout.
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In addition to that it shows how to write your own custom layout item.
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\image basicgraphicslayouts-example.png Screenshot of the Basic Layouts Example
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\section1 Window Class Definition
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The \c Window class is a subclass of QGraphicsWidget. It has a
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constructor with a QGraphicsWidget \a parent as its parameter.
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\snippet graphicsview/basicgraphicslayouts/window.h 0
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\section1 Window Class Implementation
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The constructor of \c Window instantiates a QGraphicsLinearLayout object,
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\c windowLayout, with vertical orientation. We instantiate another
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QGraphicsLinearLayout object, \c linear, whose parent is \c windowLayout.
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Next, we create a \c LayoutItem object, \c item and add it to \c linear
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with the \l{QGraphicsLinearLayout::}{addItem()} function. We also provide
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\c item with a \l{QGraphicsLinearLayout::setStretchFactor()}
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{stretchFactor}.
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\snippet graphicsview/basicgraphicslayouts/window.cpp 0
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We repeat the process:
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\list
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\li create a new \c LayoutItem,
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\li add the item \c linear, and
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\li provide a stretch factor.
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\endlist
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\snippet graphicsview/basicgraphicslayouts/window.cpp 1
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We then add \c linear to \c windowLayout, nesting two
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QGraphicsLinearLayout objects. Apart from the QGraphicsLinearLayout, we
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also use a QGraphicsGridLayout object, \c grid, which is a 4x3 grid with
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some cells spanning to other rows.
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We create seven \c LayoutItem objects and place them into \c grid with
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the \l{QGraphicsGridLayout::}{addItem()} function as shown in the code
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snippet below:
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\snippet graphicsview/basicgraphicslayouts/window.cpp 2
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The first item we add to \c grid is placed in the top left cell,
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spanning four rows. The next two items are placed in the second column,
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and they span two rows. Each item's \l{QGraphicsWidget::}{maximumHeight()}
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and \l{QGraphicsWidget::}{minimumHeight()} are set to be equal so that
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they do not expand vertically. As a result, these items will not
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fit vertically in their cells. So, we specify that they should be
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vertically aligned in the center of the cell using Qt::AlignVCenter.
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Finally, \c grid itself is added to \c windowLayout. Unlike
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QGridLayout::addItem(), QGraphicsGridLayout::addItem() requires a row
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and a column for its argument, specifying which cell the item should be
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positioned in. Also, if the \c rowSpan and \c columnSpan arguments
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are omitted, they will default to 1.
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Note that we do not specify a parent for each \c LayoutItem that we
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construct, as all these items will be added to \c windowLayout. When we
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add an item to a layout, it will be automatically reparented to the widget
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on which the layout is installed.
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\snippet graphicsview/basicgraphicslayouts/window.cpp 3
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Now that we have set up \c grid and added it to \c windowLayout, we
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install \c windowLayout onto the window object using
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QGraphicsWidget::setLayout() and we set the window title.
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\section1 LayoutItem Class Definition
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The \c LayoutItem class is a subclass of QGraphicsLayoutItem and
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QGraphicsItem. It has a constructor, a destructor, and some required
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reimplementations.
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Since it inherits QGraphicsLayoutItem it must reimplement
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{QGraphicsLayoutItem::setGeometry()}{setGeometry()} and
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{QGraphicsLayoutItem::sizeHint()}{sizeHint()}.
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In addition to that it inherits QGraphicsItem, so it must reimplement
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{QGraphicsItem::boundingRect()}{boundingRect()} and
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{QGraphicsItem::paint()}{paint()}.
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\snippet graphicsview/basicgraphicslayouts/layoutitem.h 0
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The \c LayoutItem class also has a private instance of QPixmap, \c m_pix.
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\section1 LayoutItem Class Implementation
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In \c{LayoutItem}'s constructor, \c m_pix is instantiated and the
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\c{block.png} image is loaded into it.
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\snippet graphicsview/basicgraphicslayouts/layoutitem.cpp 0
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We use the Q_UNUSED() macro to prevent the compiler from generating
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warnings regarding unused parameters.
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\snippet graphicsview/basicgraphicslayouts/layoutitem.cpp 1
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The idea behind the \c paint() function is to paint the
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background rect then paint a rect around the pixmap.
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\snippet graphicsview/basicgraphicslayouts/layoutitem.cpp 2
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The reimplementation of \l{QGraphicsItem::}{boundingRect()}
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will set the top left corner at (0,0), and the size of it will be
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the size of the layout items
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\l{QGraphicsLayoutItem::}{geometry()}. This is the area that
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we paint within.
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\snippet graphicsview/basicgraphicslayouts/layoutitem.cpp 3
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The reimplementation of \l{QGraphicsLayoutItem::setGeometry()}{setGeometry()}
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simply calls its baseclass implementation. However, since this will change
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the boundingRect we must also call
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\l{QGraphicsItem::prepareGeometryChange()}{prepareGeometryChange()}.
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Finally, we move the item according to \c geom.topLeft().
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\snippet graphicsview/basicgraphicslayouts/layoutitem.cpp 4
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Since we don't want the size of the item to be smaller than the pixmap, we
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must make sure that we return a size hint that is larger than \c m_pix.
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We also add some extra space around for borders that we will paint later.
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Alternatively, you could scale the pixmap to prevent the item from
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becoming smaller than the pixmap.
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The preferred size is the same as the minimum size hint, while we set
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maximum to be a large value
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\snippet graphicsview/basicgraphicslayouts/layoutitem.cpp 5
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*/
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