From 74f15a9e50bb1bac10ff87da83214fdeb6f9b3dd Mon Sep 17 00:00:00 2001
From: Ian C <ianc@noddybox.co.uk>
Date: Mon, 22 Oct 2018 08:01:28 +0000
Subject: Addeed snow demo.

---
 xd.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 128 insertions(+), 2 deletions(-)

diff --git a/xd.c b/xd.c
index e17461f..9f7a037 100644
--- a/xd.c
+++ b/xd.c
@@ -64,6 +64,8 @@ static const char id[]="$Id$";
 #define RND(x)		(rand()%(x))
 #define RND2(h,l)	((rand()%((h)-(l)))+(l))
 
+#define XY(x,y)		((x) + (y) * width)
+
 /* ---------------------------------------- TYPES
 */
 typedef enum {UsesImage, UsesPixmap} DType;
@@ -170,10 +172,11 @@ static void	TriangleDemo2(void);
 static void	FollowDemo(void);
 static void	CatwalkDemo(void);
 static void	GravityDemo(void);
+static void	SnowDemo(void);
 
 /* ---------------------------------------- GLOBAL VARS
 */
-#define NO_DEMOS	18
+#define NO_DEMOS	19
 
 static int		demo=NO_DEMOS-1;
 
@@ -271,6 +274,11 @@ static DemoInfo		demotbl[NO_DEMOS]=
 				GravityDemo,
 				UsesPixmap
 			    },
+			    {
+				"Snow Demo (LMB reset)",
+				SnowDemo,
+				UsesPixmap
+			    },
 			};
 
 /* ---------------------------------------- X11 VARS
@@ -4057,7 +4065,7 @@ static void GravityDemo(void)
 		gravobj[f].dx = sintab[a] * 0.1;
 		gravobj[f].dy = costab[a] * 0.1;
 
-		gravobj[f].mass = 1;
+		gravobj[f].mass = 10;
 		gravobj[f].alive = TRUE;
 	    }
 
@@ -4164,4 +4172,122 @@ static void GravityDemo(void)
 #undef GRAV_SIZE
 
 
+/* ---------------------------------------- SNOW DEMO
+ */
+
+#define SNOW_LINES	20
+#define SNOW_FLAKES	10000
+
+static void SnowDemo(void)
+{
+    static int init = FALSE;
+
+    static int *map;
+
+    typedef struct
+    {
+    	int	x,y;
+    } Flake;
+
+    static Flake *snow;
+
+    int f,r;
+    int x,y;
+    int xi, yi;
+
+    if (!init || mouse_b&Button1Mask)
+    {
+	Cls();
+
+	map = Grab(sizeof *map * width * height);
+	snow = Grab(sizeof *snow * SNOW_FLAKES);
+
+	Line(0, 0, 0, height - 1, red);
+	Line(width - 1, 0, width - 1, height - 1, red);
+	Line(0, height - 1, width - 1, height - 1, red);
+
+	for(x = 0; x < width; x++)
+	{
+	    for(y = 0; y < height; y++)
+	    {
+		if (x == 0 || x == width - 1 || y == height - 1)
+		{
+		    map[XY(x,y)] = 1;
+		}
+		else
+		{
+		    map[XY(x,y)] = 0;
+		}
+	    }
+	}
+
+	for(f = 0; f < SNOW_LINES; f++)
+	{
+	    x = RND(width);
+	    y = RND(height);
+	    do
+	    {
+		xi = RND2(1, -1);
+	    } while (xi == 0);
+	    yi = 0;
+
+	    for(r = RND(50) + 10; r > 0; r--)
+	    {
+	    	if (x > 0 && x < width && y > 0 && y < height)
+		{
+		    Plot(x, y, red);
+		    map[XY(x,y)] = 1;
+		    x += xi;
+		    y += yi;
+		}
+	    }
+	}
+
+	for(f = 0; f < SNOW_FLAKES; f++)
+	{
+	    do
+	    {
+		snow[f].x = RND(width - 2) + 1;
+		snow[f].y = RND(height);
+	    } while (map[XY(snow[f].x, snow[f].y)]);
+	}
+
+	init=TRUE;
+    }
+
+    for(f = 0; f < SNOW_FLAKES; f++)
+    {
+    	if (map[XY(snow[f].x, snow[f].y + 1)] == 0)
+	{
+	    Plot(snow[f].x, snow[f].y, black);
+	    snow[f].y++;
+	    Plot(snow[f].x, snow[f].y, white);
+	}
+	else if (map[XY(snow[f].x + 1, snow[f].y + 1)] == 0)
+	{
+	    Plot(snow[f].x, snow[f].y, black);
+	    snow[f].x++;
+	    snow[f].y++;
+	    Plot(snow[f].x, snow[f].y, white);
+	}
+	else if (map[XY(snow[f].x - 1, snow[f].y + 1)] == 0)
+	{
+	    Plot(snow[f].x, snow[f].y, black);
+	    snow[f].x--;
+	    snow[f].y++;
+	    Plot(snow[f].x, snow[f].y, white);
+	}
+	else
+	{
+	    Plot(snow[f].x, snow[f].y, white);
+	    map[XY(snow[f].x, snow[f].y)] = 1;
+	    snow[f].x = RND(width - 2) + 1;
+	    snow[f].y = 0;
+	}
+    }
+}
+
+#undef SNOW_LINES
+
+
 /* END OF FILE */
-- 
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