From d1fd4d0a3234789102b6b46869a1bfc9906f336f Mon Sep 17 00:00:00 2001
From: Enrico Zini <enrico@enricozini.org>
Date: Wed, 9 Dec 2009 23:53:40 +0000
Subject: [PATCH] Simplified calculations a bit

---
 src/fisheye.vala | 115 +++++++++++++++++++++--------------------------
 1 file changed, 51 insertions(+), 64 deletions(-)

diff --git a/src/fisheye.vala b/src/fisheye.vala
index e8a660a..c40c8a7 100644
--- a/src/fisheye.vala
+++ b/src/fisheye.vala
@@ -40,7 +40,6 @@ public class FisheyeList : Gtk.DrawingArea
 	protected int focus_end;
 	protected int[] focus_starts;
 	protected bool focus_locked;
-	protected int focus_centre;
 	protected bool focus_layout_needed;
 
 	protected int _focus_size;
@@ -54,16 +53,6 @@ public class FisheyeList : Gtk.DrawingArea
 		}
 	}
 
-	protected int _distortion_factor;
-	public int distortion_factor {
-		get { return _distortion_factor; }
-		set {
-			_distortion_factor = value;
-			focus_layout_needed = true;
-			queue_draw();
-		}
-	}
-
 	protected int _label_column;
 	public int label_column {
 		get { return _label_column; }
@@ -90,11 +79,9 @@ public class FisheyeList : Gtk.DrawingArea
 
 		// Defaults for properties
 		focus_size = 20;
-		distortion_factor = 30;
 		label_column = 0;
 
 		cur_el = 0;
-		focus_centre = 0;
 		focus_locked = false;
 
 		add_events(Gdk.EventMask.POINTER_MOTION_MASK
@@ -230,10 +217,8 @@ public class FisheyeList : Gtk.DrawingArea
 
 	protected int el_y(int idx)
 	{
-		// Undistorted Y
-		int undy = idx * allocation.height / label_cache.length;
 		// Distorted position
-		int pos = fisheye(undy, focus_centre, _distortion_factor, 0, allocation.height);
+		int pos = fisheye(idx);
 		//stderr.printf("%d %f %f\n", idx, undy, pos);
 		return pos;
 	}
@@ -272,29 +257,18 @@ public class FisheyeList : Gtk.DrawingArea
 	{
 		if (label_cache.length == 0)
 		{
-			focus_centre = 0;
 			focus_first = 0;
 			focus_end = 0;
 			focus_starts[0] = 0;
 		} else {
-			// Anchor point
-			focus_centre = cur_el*allocation.height/label_cache.length;
-
 			focus_first = cur_el > _focus_size/2 ? cur_el-_focus_size/2 : 0;
 			focus_end = focus_first + _focus_size;
 			if (focus_end >= label_cache.length) focus_end = label_cache.length;
 
 			// Compute starting positions for all items in focus
-			for (int idx = focus_first; idx < focus_end; ++idx)
+			for (int idx = focus_first; idx <= focus_end; ++idx)
 			{
-				int posprev = idx == 0 ? 0 : el_y(idx-1);
-				int pos = el_y(idx);
-				int posnext = idx == label_cache.length-1 ? 1 : el_y(idx+1);
-				int y0 = (pos+posprev)/2;
-				int y1 = (pos+posnext)/2;
-
-				focus_starts[idx - focus_first] = y0;
-				focus_starts[idx - focus_first + 1] = y1;
+				focus_starts[idx - focus_first] = el_y(idx);
 			}
 		}
 		focus_layout_needed = false;
@@ -369,41 +343,54 @@ public class FisheyeList : Gtk.DrawingArea
 		}
 	}
 
-    /*
-     * The following function is adapted from Prefuse's FisheyeDistortion.java.
-     *
-     * A relevant annotation from Prefuse:
-     *
-     * For more details on this form of transformation, see Manojit Sarkar and 
-     * Marc H. Brown, "Graphical Fisheye Views of Graphs", in Proceedings of 
-     * CHI'92, Human Factors in Computing Systems, p. 83-91, 1992. Available
-     * online at <a href="http://citeseer.ist.psu.edu/sarkar92graphical.html">
-     * http://citeseer.ist.psu.edu/sarkar92graphical.html</a>. 
-     */
-
-    /*
-     * Distorts an item's coordinate.
-     * @param x the undistorted coordinate
-     * @param coordinate of the anchor or focus point
-     * @param d disortion factor
-     * @param min the beginning of the display
-     * @param max the end of the display
-     * @return the distorted coordinate
-     */
-    private int fisheye(int x, int a, int d, int min, int max)
-    {
-        if ( d != 0 ) {
-            bool left = x<a;
-            double v;
-	    int m = (left ? a-min : max-a);
-            if ( m == 0 ) m = max-min;
-            v = (double)(x - a).abs() / m;
-            v = (double)(d+1)/(d+(1/v));
-            return (int)Math.round((left?-1:1)*m*v + a);
-        } else {
-            return x;
-        }
-    }
+	/*
+	 * The following function is adapted from Prefuse's FisheyeDistortion.java.
+	 *
+	 * A relevant annotation from Prefuse:
+	 *
+	 * For more details on this form of transformation, see Manojit Sarkar and 
+	 * Marc H. Brown, "Graphical Fisheye Views of Graphs", in Proceedings of 
+	 * CHI'92, Human Factors in Computing Systems, p. 83-91, 1992. Available
+	 * online at <a href="http://citeseer.ist.psu.edu/sarkar92graphical.html">
+	 * http://citeseer.ist.psu.edu/sarkar92graphical.html</a>. 
+	 */
+
+	/*
+	 * Distorts an item's coordinate.
+	 * @param x the undistorted coordinate
+	 * @param coordinate of the anchor or focus point
+	 * @param d disortion factor
+	 * @param min the beginning of the display
+	 * @param max the end of the display
+	 * @return the distorted coordinate
+	 */
+	private int fisheye(int idx)
+	{
+		// Autocompute distortion factor
+		// 20 is the pixel size of the item at centre of focus
+		double d = label_cache.length * 20 / allocation.height;
+		if ( d <= 1 )
+			return idx * allocation.height / label_cache.length;
+
+		double a = (double)cur_el * allocation.height / label_cache.length;
+		double x = (double)idx * allocation.height / label_cache.length;
+		double max = (double)allocation.height;
+
+		if (idx < cur_el)
+		{
+			double m = a;
+			if ( m == 0 ) m = max;
+			double v = (double)(a - x) / m;
+			v = (double)(d+1)/(d+(1/v));
+			return (int)Math.round(a - m*v);
+		} else {
+			double m = max-a;
+			if ( m == 0 ) m = max;
+			double v = (double)(x - a) / m;
+			v = (double)(d+1)/(d+(1/v));
+			return (int)Math.round(a + m*v);
+		}
+	}
 }
 
 public class Fisheye : Gtk.Window
-- 
2.30.2