From ef83b9d6c26c443f34f5f81cdcf1d2b596e822e5 Mon Sep 17 00:00:00 2001
From: Ian C <ianc@noddybox.co.uk>
Date: Wed, 4 Jan 2017 14:08:46 +0000
Subject: Added follow demo.

---
 xd.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 103 insertions(+), 1 deletion(-)

diff --git a/xd.c b/xd.c
index 7246c5c..e544851 100644
--- a/xd.c
+++ b/xd.c
@@ -51,6 +51,7 @@ static const char id[]="$Id$";
 #endif
 
 #define RAD(x)  ((x)*M_PI/180.0)
+#define DEG(x)  ((x)/(M_PI/180.0))
 
 #define MIN(a,b)	((a)<(b)?(a):(b))
 #define MAX(a,b)	((a)>(b)?(a):(b))
@@ -163,10 +164,11 @@ static void	PolyDropDemo(void);
 static void	CraterDemo(void);
 static void	TriangleDemo(void);
 static void	TriangleDemo2(void);
+static void	FollowDemo(void);
 
 /* ---------------------------------------- GLOBAL VARS
 */
-#define NO_DEMOS	15
+#define NO_DEMOS	16
 
 static int		demo=NO_DEMOS-1;
 
@@ -249,6 +251,11 @@ static DemoInfo		demotbl[NO_DEMOS]=
 				TriangleDemo2,
 				UsesPixmap
 			    },
+			    {
+				"Following swarm",
+				FollowDemo,
+				UsesPixmap
+			    },
 			};
 
 /* ---------------------------------------- X11 VARS
@@ -3648,4 +3655,99 @@ static void TriangleDemo2(void)
 }
 
 
+/* END OF FILE */
+
+
+/* ---------------------------------------- FOLLOW DEMO
+ */
+#define FOLLOW_NUM	4000
+#define FOLLOW_SPEED	1
+#define FOLLOW_WEIGHT	0.001
+
+static void FollowDemo(void)
+{
+    static int init=FALSE;
+    static double x[FOLLOW_NUM];
+    static double y[FOLLOW_NUM];
+    static double dx[FOLLOW_NUM];
+    static double dy[FOLLOW_NUM];
+
+    int f,r;
+    int newa;
+
+    if (!init || mouse_b&Button1Mask)
+    {
+	for(f = 0; f < FOLLOW_NUM; f++)
+	{
+	    x[f] = RND(width);
+	    y[f] = RND(height);
+	    dx[f] = 0;
+	    dy[f] = 0;
+	}
+
+	init = TRUE;
+    }
+
+    Cls();
+
+    for(f = 0; f < FOLLOW_NUM; f++)
+    {
+    	double d_x,d_y,d;
+
+	d_x = mouse_x - x[f];
+	d_y = mouse_y - y[f];
+
+	if (d_x == 0)
+	{
+	    d_x = 0.0001;
+	}
+
+	if (d_y == 0)
+	{
+	    d_y = 0.0001;
+	}
+
+	if (fabs(d_x) > fabs(d_y))
+	{
+	    d = fabs(d_x);
+	}
+	else
+	{
+	    d = fabs(d_y);
+	}
+
+	d_x = d_x / d * FOLLOW_WEIGHT;
+	d_y = d_y / d * FOLLOW_WEIGHT;
+
+	dx[f] += d_x;
+	dy[f] += d_y;
+
+	if (dx[f] < -FOLLOW_SPEED)
+	{
+	    dx[f] = -FOLLOW_SPEED;
+	}
+
+	if (dx[f] > FOLLOW_SPEED)
+	{
+	    dx[f] = FOLLOW_SPEED;
+	}
+
+	if (dy[f] < -FOLLOW_SPEED)
+	{
+	    dy[f] = -FOLLOW_SPEED;
+	}
+
+	if (dy[f] > FOLLOW_SPEED)
+	{
+	    dy[f] = FOLLOW_SPEED;
+	}
+
+	x[f] += dx[f];
+	y[f] += dy[f];
+
+	Line(x[f], y[f], x[f]-dx[f], y[f]-dy[f], red);
+    }
+}
+
+
 /* END OF FILE */
-- 
cgit v1.2.3