Update Qt Charts legend example to illustrate interactivity

Example cleaned up and organized, and interactive checkbox is added to
allow user to see how an interactive legend works.

Task-number: QTBUG-93477
Change-Id: I855283ad8fffd61b23cf021ab41530255abfbd47
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

3 files changed, 34 insertions, 14 deletions

diff --git a/src/charts/doc/images/examples_legend_detach.png b/src/charts/doc/images/examples_legend_detach.png
index 3376a4a0..867c17a6 100644
--- a/src/charts/doc/images/examples_legend_detach.png
+++ b/src/charts/doc/images/examples_legend_detach.png
diff --git a/src/charts/doc/images/examples_legend_detach2.png b/src/charts/doc/images/examples_legend_detach2.png
index 5cc33819..5efe0d84 100644
--- a/src/charts/doc/images/examples_legend_detach2.png
+++ b/src/charts/doc/images/examples_legend_detach2.png
diff --git a/src/charts/doc/src/examples-legend.qdoc b/src/charts/doc/src/examples-legend.qdoc
index c9d976d9..0d543c7d 100644
--- a/src/charts/doc/src/examples-legend.qdoc
+++ b/src/charts/doc/src/examples-legend.qdoc
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the documentation of the Qt Toolkit.
@@ -32,16 +32,24 @@
 
     \brief This example shows how to detach the legend from the chart and how to attach it back.
 
-    By default the chart draws the legend inside the same view with the chart. In some cases the
-    user may want to draw the legend to somewhere else. To make this possible the legend can be
-    detached from the chart. Detaching means that the chart doesn't draw the legend or try to
-    change its layout. Detached legend can then be drawn wherever the user wishes, for example,
-    in a different graphics scene. The behavior of the legend can be inspected by running the
-    legend example.
-    In the example we use the bar series where we add or remove the bar sets. The legend reflects
-    the changes in series. The legend can be detached or attached back to the chart and its
-    alignment can be modified.
-    When the legend is detached, it can be resized and positioned freely.
+    By default, the chart draws the legend inside the same graphics view the chart is contained
+    within. In some cases, the user may want to draw the legend somewhere else. To make this
+    possible, the legend can be detached from the chart. Detaching means that the legend is no
+    longer fixed to an edge of the chart, and the chart no longer controls the legend's layout.
+    Instead, the legend geometry is controlled by the user, allowing free control of the location
+    and size of the legend. This can be floating atop the content of the chart, or even drawn in a
+    different graphics scene. The behavior of the legend can be tested by running this example.
+
+    In this example we show a bar series, allowing bar sets to be added or removed interactively.
+    The legend reflects the changes in series as bar sets are added and/or removed. The attachment
+    of the legend, its alignment, and its ability to be moved and resized can be controlled using
+    methods in \c QLegend.
+
+    When the legend is detached, it can be resized and positioned freely. If the interactive
+    feature of the legend is enabled, the legend can be freely dragged and resized by the user.
+    If the user drags the legend off of any side of the chart, it will automatically re-attach to
+    that side of the chart.
+
 
     \image examples_legend_detach.png
     \image examples_legend_detach2.png
@@ -54,15 +62,27 @@
 
     \snippet legend/mainwidget.cpp 1
 
-    This snippet shows how to detach the legend from the chart. After detaching, we turn its background to visible and set a different color to it. This makes it easier to see how the items inside the legend are arranged in detached mode.
+    This snippet shows how to detach the legend from the chart.
 
     \snippet legend/mainwidget.cpp 2
 
-    Here we attach the legend back to the chart. The background is turned invisible.
+    Here we reattach the legend to the chart. The background is turned invisible.
 
     \snippet legend/mainwidget.cpp 3
 
-    This shows how we set the detached legend dimensions. After setting the new values, we call update to show changes on screen.
+    Here we connect to the signal emitted when the legend is detached or attached, turning its
+    background on when detached and off when attached. This makes it easier to see how the
+    items inside the legend are arranged when it is detached.
 
     \snippet legend/mainwidget.cpp 4
+
+    This shows how to make the legend interactive to the user using a pointing device such as a
+    mouse.
+
+    \snippet legend/mainwidget.cpp 5
+
+    This shows how we set the detached legend dimensions if the legend is not interactive. After
+    setting the new values, we call update to show changes on screen.
+
+    \snippet legend/mainwidget.cpp 6
 */