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+
+/*
+    Rosegarden
+    A sequencer and musical notation editor.
+
+    This program is Copyright 2000-2008
+        Guillaume Laurent   <[email protected]>,
+        Chris Cannam        <[email protected]>,
+        Richard Bown        <[email protected]>
+
+    The moral right of the authors to claim authorship of this work
+    has been asserted.
+
+    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 _RULER_SCALE_H_
+#define _RULER_SCALE_H_
+
+#include "Event.h"
+
+namespace Rosegarden {
+
+class Composition;
+
+/**
+ * RulerScale is a base for classes that may be queried in order to
+ * discover the correct x-coordinates for bar lines and bar
+ * subdivisions.
+ *
+ * RulerScale does not contain any methods that relate bar numbers
+ * to times, time signature or duration -- those are in Composition.
+ *
+ * The methods in RulerScale should return extrapolated (but valid)
+ * results even when passed a bar number outside the theoretically
+ * visible or existant bar range.
+ *
+ * Apart from getBarPosition, every method in this class has a
+ * default implementation, which should work correctly provided
+ * the subclass maintains spacing proportional to time within a
+ * bar, but which may not be an efficient implementation for any
+ * given subclass.
+ * 
+ * (Potential to-do: At the moment all our RulerScales are used in
+ * contexts where spacing proportional to time within a bar is the
+ * only interpretation that makes sense, so this is okay.  In
+ * theory though we should probably subclass out these "default"
+ * implementations into an intermediate abstract class.)
+ */
+
+class RulerScale
+{
+public:
+    virtual ~RulerScale();
+    Composition *getComposition() const { return m_composition; }
+
+    /**
+     * Return the number of the first visible bar.
+     */
+    virtual int getFirstVisibleBar() const;
+
+    /**
+     * Return the number of the last visible bar.  (The last
+     * visible bar_line_ will be at the end of this bar.)
+     */
+    virtual int getLastVisibleBar() const;
+
+    /**
+     * Return the x-coordinate at which bar number n starts.
+     */
+    virtual double getBarPosition(int n) const = 0;
+
+    /**
+     * Return the width of bar number n.
+     */
+    virtual double getBarWidth(int n) const;
+
+    /**
+     * Return the width of each beat subdivision in bar n.
+     */
+    virtual double getBeatWidth(int n) const;
+
+    /**
+     * Return the number of the bar containing the given x-coord.
+     */
+    virtual int getBarForX(double x) const;
+
+    /**
+     * Return the nearest time value to the given x-coord.
+     */
+    virtual timeT getTimeForX(double x) const;
+
+    /**
+     * Return the x-coord corresponding to the given time value.
+     */
+    virtual double getXForTime(timeT time) const;
+
+    /**
+     * Return the duration corresponding to the given delta-x
+     * starting at the given x-coord.
+     */
+    virtual timeT getDurationForWidth(double x, double width) const;
+
+    /**
+     * Return the width corresponding to the given duration
+     * starting at the given time.
+     */
+    virtual double getWidthForDuration(timeT startTime, timeT duration) const;
+
+    /**
+     * Return the width of the entire scale.
+     */
+    virtual double getTotalWidth() const;
+
+protected:
+    RulerScale(Composition *c);
+    Composition *m_composition;
+};
+
+
+/**
+ * SimpleRulerScale is an implementation of RulerScale that maintains
+ * a strict proportional correspondence between x-coordinate and time.
+ */
+
+class SimpleRulerScale : public RulerScale
+{
+public:
+    /**
+     * Construct a SimpleRulerScale for the given Composition, with a
+     * given origin and x-coord/time ratio.  (For example, a ratio of
+     * 10 means that one pixel equals 10 time units.)
+     */
+    SimpleRulerScale(Composition *composition,
+                     double origin, double unitsPerPixel);
+    virtual ~SimpleRulerScale();
+
+    double getOrigin() const { return m_origin; }
+    void   setOrigin(double origin) { m_origin = origin; }
+
+    double getUnitsPerPixel() const { return m_ratio; }
+    void   setUnitsPerPixel(double ratio) { m_ratio = ratio; }
+
+    virtual double getBarPosition(int n) const;
+    virtual double getBarWidth(int n) const;
+    virtual double getBeatWidth(int n) const;
+    virtual int getBarForX(double x) const;
+    virtual timeT getTimeForX(double x) const;
+    virtual double getXForTime(timeT time) const;
+
+protected:
+    double m_origin;
+    double m_ratio;
+
+private:
+    SimpleRulerScale(const SimpleRulerScale &ruler);
+    SimpleRulerScale &operator=(const SimpleRulerScale &ruler);
+};
+
+}
+
+#endif