diff base/ZoomConstraint.h @ 0:fc9323a41f5a

start base : Sonic Visualiser sv1-1.0rc1

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/base/ZoomConstraint.h	Fri May 11 09:08:14 2007 +0000
@@ -0,0 +1,66 @@
+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    Sonic Visualiser
+    An audio file viewer and annotation editor.
+    Centre for Digital Music, Queen Mary, University of London.
+    This file copyright 2006 Chris Cannam.
+    
+    This program is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License as
+    published by the Free Software Foundation; either version 2 of the
+    License, or (at your option) any later version.  See the file
+    COPYING included with this distribution for more information.
+*/
+
+#ifndef _ZOOM_CONSTRAINT_H_
+#define _ZOOM_CONSTRAINT_H_
+
+#include <stdlib.h>
+
+/**
+ * ZoomConstraint is a simple interface that describes a limitation on
+ * the available zoom sizes for a view, for example based on cache
+ * strategy or a (processing) window-size limitation.
+ *
+ * The default ZoomConstraint imposes no actual constraint except for
+ * a nominal maximum.
+ */
+
+class ZoomConstraint
+{
+public:
+    virtual ~ZoomConstraint() { }
+
+    enum RoundingDirection {
+	RoundDown,
+	RoundUp,
+	RoundNearest
+    };
+
+    /**
+     * Given the "ideal" block size (frames per pixel) for a given
+     * zoom level, return the nearest viable block size for this
+     * constraint.
+     *
+     * For example, if a block size of 1523 frames per pixel is
+     * requested but the underlying model only supports value
+     * summaries at powers-of-two block sizes, return 1024 or 2048
+     * depending on the rounding direction supplied.
+     */
+    virtual size_t getNearestBlockSize(size_t requestedBlockSize,
+				       RoundingDirection = RoundNearest)
+	const
+    {
+	if (requestedBlockSize > getMaxZoomLevel()) return getMaxZoomLevel();
+	else return requestedBlockSize;
+    }
+
+    /**
+     * Return the maximum zoom level within range for this constraint.
+     */
+    virtual size_t getMaxZoomLevel() const { return 262144; }
+};
+
+#endif
+