Initial import from the monolithic Qt.

This is the beginning of revision history for this module. If you
want to look at revision history older than this, please refer to the
Qt Git wiki for how to use Git history grafting. At the time of
writing, this wiki is located here:

http://qt.gitorious.org/qt/pages/GitIntroductionWithQt

If you have already performed the grafting and you don't see any
history beyond this commit, try running "git log" with the "--follow"
argument.

Branched from the monolithic repo, Qt master branch, at commit
896db169ea224deb96c59ce8af800d019de63f12

1 files changed, 83 insertions, 0 deletions

diff --git a/doc/src/examples/contiguouscache.qdoc b/doc/src/examples/contiguouscache.qdoc
new file mode 100644
index 0000000000..2200b92e9a
--- /dev/null
+++ b/doc/src/examples/contiguouscache.qdoc
@@ -0,0 +1,83 @@
+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:FDL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Free Documentation License
+** Alternatively, this file may be used under the terms of the GNU Free
+** Documentation License version 1.3 as published by the Free Software
+** Foundation and appearing in the file included in the packaging of this
+** file.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \example tools/contiguouscache
+    \title Contiguous Cache Example
+
+    The Contiguous Cache example shows how to use QContiguousCache to manage memory usage for
+    very large models.  In some environments memory is limited and, even when it
+    isn't, users still dislike an application using excessive memory.
+    Using QContiguousCache to manage a list, rather than loading
+    the entire list into memory, allows the application to limit the amount
+    of memory it uses, regardless of the size of the data set it accesses
+
+    The simplest way to use QContiguousCache is to cache as items are requested. When
+    a view requests an item at row N it is also likely to ask for items at rows near
+    to N.
+
+    \snippet examples/tools/contiguouscache/randomlistmodel.cpp 0
+
+    After getting the row, the class determines if the row is in the bounds
+    of the contiguous cache's current range.  It would have been equally valid to
+    simply have the following code instead.
+
+    \code
+    while (row > m_rows.lastIndex())
+        m_rows.append(fetchWord(m_rows.lastIndex()+1);
+    while (row < m_rows.firstIndex())
+        m_rows.prepend(fetchWord(m_rows.firstIndex()-1);
+    \endcode
+
+    However a list will often jump rows if the scroll bar is used directly, resulting in
+    the code above causing every row between the old and new rows to be fetched.
+
+    Using QContiguousCache::lastIndex() and QContiguousCache::firstIndex() allows
+    the example to determine what part of the list the cache is currently caching.
+    These values don't represent the indexes into the cache's own memory, but rather
+    a virtual infinite array that the cache represents.
+
+    By using QContiguousCache::append() and QContiguousCache::prepend() the code ensures
+    that items that may be still on the screen are not lost when the requested row
+    has not moved far from the current cache range.  QContiguousCache::insert() can
+    potentially remove more than one item from the cache as QContiguousCache does not
+    allow for gaps.  If your cache needs to quickly jump back and forth between
+    rows with significant gaps between them consider using QCache instead.
+
+    And thats it.  A perfectly reasonable cache, using minimal memory for a very large
+    list.  In this case the accessor for getting the words into the cache
+    generates random information rather than fixed information.  This allows you 
+    to see how the cache range is kept for a local number of rows when running the
+    example.
+
+    \snippet examples/tools/contiguouscache/randomlistmodel.cpp 1
+
+    It is also worth considering pre-fetching items into the cache outside of the
+    application's paint routine.  This can be done either with a separate thread
+    or using a QTimer to incrementally expand the range of the cache prior to
+    rows being requested out of the current cache range.
+*/