Add example for showing graph legend

+Fix default theme

Task-number: QTRD-2653
Change-Id: Iccf4161cd19a9dfe6226189568efeb4565ba53ed
Reviewed-by: Tomi Korpipää <tomi.korpipaa@digia.com>

1 files changed, 67 insertions, 0 deletions

diff --git a/examples/qmllegend/doc/src/qmllegend.qdoc b/examples/qmllegend/doc/src/qmllegend.qdoc
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+/****************************************************************************
+**
+** Copyright (C) 2013 Digia Plc
+** All rights reserved.
+** For any questions to Digia, please use contact form at http://qt.digia.com
+**
+** This file is part of the QtDataVisualization module.
+**
+** Licensees holding valid Qt Enterprise licenses may use this file in
+** accordance with the Qt Enterprise License Agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and Digia.
+**
+** If you have questions regarding the use of this file, please use
+** contact form at http://qt.digia.com
+**
+****************************************************************************/
+
+/*!
+    \example qmllegend
+    \title Qt Quick 2 Legend Example
+    \ingroup qtdatavisualization_examples
+    \brief Showing graph legend in a QML application.
+
+    The Qt Quick 2 legend example shows how to make an interactive legend for a graph.
+
+    \image qmllegend-example.png
+
+    The interesting thing about this example is displaying the legend. We'll concentrate on
+    thate and skip explaining the basic functionality - for
+    more detailed QML example documentation, see \l{Qt Quick 2 Scatter Example}.
+
+    \section1 Legend
+
+    The legend is simply a column of custom \c LegendItem items inside a transparent rectangle.
+    Each item is supplied with a series and the graph theme:
+
+    \snippet ../examples/qmllegend/qml/qmllegend/main.qml 0
+
+    The legend items consist of a marker rectangle, which indicates the color of the series,
+    and a text field, which shows the name of the series. The colors we get from the series and
+    the theme supplied at legend item initialization:
+
+    \snippet ../examples/qmllegend/qml/qmllegend/legenditem.qml 0
+    \dots 4
+    \snippet ../examples/qmllegend/qml/qmllegend/legenditem.qml 1
+
+    We want the legend to be interactive, so we add additional logic to enable selection of a
+    series by clicking on a legend item, as well as highlighting the legend item corresponding
+    to the selected series.
+
+    The highlight depends on the selection state of the series, so we define two states, which
+    follow the Bar3DSeries::selectedBar property and adjust the \c legendItem color appropriately:
+
+    \snippet ../examples/qmllegend/qml/qmllegend/legenditem.qml 3
+
+    To make the legend item interactive, we define a MouseArea to detect clicks on it and adjust
+    the series selection accordingly:
+
+    \snippet ../examples/qmllegend/qml/qmllegend/legenditem.qml 2
+
+    The \c previousSelection used above is another custom property of \c LegendItem, which we update
+    whenever selection changes on the series. This way we remember the last selected bar of
+    each series:
+
+    \snippet ../examples/qmllegend/qml/qmllegend/legenditem.qml 4
+*/