From d3a98cf6cbc3bd0b9efc570f58e8812c03931c18 Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Tue, 16 Oct 2018 10:08:48 +0200
Subject: Original 5.40

---
 hacks/celtic.c | 1131 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1131 insertions(+)
 create mode 100644 hacks/celtic.c

(limited to 'hacks/celtic.c')

diff --git a/hacks/celtic.c b/hacks/celtic.c
new file mode 100644
index 0000000..890b398
--- /dev/null
+++ b/hacks/celtic.c
@@ -0,0 +1,1131 @@
+/* celtic, Copyright (c) 2006 Max Froumentin <max@lapin-bleu.net>
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that
+ * copyright notice and this permission notice appear in supporting
+ * documentation.  No representations are made about the suitability of this
+ * software for any purpose.  It is provided "as is" without express or 
+ * implied warranty.
+ *
+ * A celtic pattern programme inspired by "Les Entrelacs Celtes", by
+ * Christian Mercat, Dossier Pour La Science, no. 47, april/june 2005.
+ * See <http://www.entrelacs.net/>
+ */
+
+#include <math.h>
+#include "screenhack.h"
+#include "erase.h"
+
+#define SQRT_3 1.73205080756887729352
+#undef assert
+#define assert(EXP) do { if (!((EXP))) abort(); } while(0)
+
+/*-----------------------------------------*/
+
+struct params {
+  unsigned long curve_width, shadow_width;
+  double shape1, shape2;
+  unsigned long margin;
+
+  enum graph_type { polar, tgrid, kennicott, triangle } type;
+  unsigned long edge_size;
+  unsigned long cluster_size; /* only used if type is kennicott */
+  unsigned long delay;        /* controls curve drawing speed (step delay 
+			       * in microsecs) */
+  unsigned long nsteps; /* only if triangle: number of subdivisions along the side */
+  unsigned long nb_orbits;          /* only used if type is polar */
+  unsigned long nb_nodes_per_orbit; /* only used if type is polar */
+
+  double angle; /* angle of rotation of the graph around the centre */
+};
+
+/*-----------------------------------------*/
+typedef enum direction {
+  CLOCKWISE=0, ANTICLOCKWISE=1
+} Direction;
+
+
+/*-----------------------------------------*/
+typedef struct array {
+  int nb_elements;
+  int nb_allocated_elements;
+  int increment;
+  void **elements;
+} *Array;
+
+typedef struct graph {
+  Array nodes;
+  Array edges;
+} *Graph;
+
+typedef struct edge_couple {
+  int **array;
+  int size;
+} *EdgeCouple;
+
+typedef struct pattern {
+  double shape1, shape2;
+  EdgeCouple ec;
+  Graph graph;
+  Array splines;
+  int ncolors;
+} *Pattern;
+
+struct state {
+  Display *dpy;
+  Window window;
+  eraser_state *eraser;
+
+  int ncolors;
+  XColor *colors;
+  GC gc,shadow_gc,gc_graph;
+
+  Bool showGraph;
+  Pattern pattern;
+  Graph graph;
+  XWindowAttributes xgwa;
+  int delay2;
+  int reset, force_reset;
+  double t;
+
+  struct params params;
+};
+
+
+
+
+static Array array_new(int increment)
+{
+  Array new;
+  assert(new=(Array)calloc(1,sizeof(struct array)));
+  new->nb_elements=0;
+  new->nb_allocated_elements=0;
+  new->increment=increment;
+  return new;
+}
+
+static void array_del(Array a, void (*free_element)(void*))
+{
+  int i;
+  if (free_element) 
+    for (i=0;i<a->nb_elements;i++) 
+      free_element(a->elements[i]);
+  free(a->elements);
+  free(a);
+}
+
+static void array_add_element(Array a, void *element)
+{
+  if (a->nb_elements == a->nb_allocated_elements) {
+    /* we must allocate more */
+    a->nb_allocated_elements+=a->increment;
+    a->elements=realloc(a->elements,a->nb_allocated_elements*sizeof(void *));
+  }
+  a->elements[a->nb_elements++]=element;
+}
+/*-----------------------------------------*/
+
+typedef struct node {
+  double x,y;
+  Array edges;
+} *Node;
+
+typedef struct edge {
+  Node node1, node2;
+  double angle1, angle2;
+} *Edge;
+
+/*-----------------------------------------*/
+/* Node functions */
+
+static Node node_new(double x, double y)
+{
+  Node new;
+  assert(new = (Node)calloc(1,sizeof(struct node)));
+  new->x=x;
+  new->y=y;
+  new->edges = array_new(10);
+  return new;
+}
+
+static void node_del(void *n) 
+{ /* not Node * because the function is passed to array_del */
+  array_del(((Node)n)->edges,NULL);
+  free(n);
+}
+
+#if 0
+static void node_to_s(Node n, FILE *f) 
+{
+  fprintf(f,"Node: %g %g\n",n->x,n->y);
+}
+#endif
+
+static void node_draw(struct state *st, Node n)
+{
+  XDrawArc(st->dpy,st->window,st->gc_graph,(int)rint(n->x)-5,(int)rint(n->y)-5,10,10,0,360*64);
+}
+  
+static void node_add_edge(Node n, Edge e)
+{
+  array_add_element(n->edges,e);
+}
+
+
+/*-----------------------------------------*/
+/* Edge functions */
+
+static Edge edge_new(Node n1, Node n2)
+{
+  Edge new; 
+  assert(new = (Edge)calloc(1,sizeof(struct edge)));
+  new->node1=n1;
+  new->node2=n2;
+  new->angle1=atan2(new->node2->y - new->node1->y, new->node2->x - new->node1->x);
+  if (new->angle1 < 0) new->angle1+=6.28;
+
+  new->angle2=atan2(new->node1->y - new->node2->y, new->node1->x - new->node2->x);
+  if (new->angle2 < 0) new->angle2+=6.28;
+  return new;
+}
+
+static void edge_del(void *e) /* not Edge * because the function is passed to array_del */
+{
+  free(e);
+}
+
+#if 0
+static void edge_to_s(Edge e, FILE *f)
+{
+  fprintf(f,"Edge: (%g, %g), (%g, %g) angles: %g, %g\n",
+	  e->node1->x, e->node1->y, e->node2->x, e->node2->y,
+	  e->angle1, e->angle2);
+}
+#endif
+
+static void edge_draw(struct state *st, Edge e)
+{
+  XDrawLine(st->dpy,st->window,st->gc_graph, e->node1->x, e->node1->y, e->node2->x, e->node2->y);
+}
+
+static double edge_angle(Edge e, Node n)
+{
+  /* returns the angle of the edge at Node n */
+  assert(n==e->node1 || n==e->node2);
+  if (n==e->node1) return e->angle1; else return e->angle2;
+}
+
+static Node edge_other_node(Edge e, Node n)
+{
+  assert(n==e->node1 || n==e->node2);
+  if (n==e->node1) return e->node2; else return e->node1;
+}
+
+static double edge_angle_to(Edge e, Edge e2, Node node, Direction direction)
+{
+  /* returns the absolute angle from this edge to "edge2" around
+     "node" following "direction" */
+  double a;
+
+  if (direction==CLOCKWISE)
+    a=edge_angle(e,node) - edge_angle(e2,node);
+  else
+    a=edge_angle(e2,node) - edge_angle(e,node);
+
+  if (a<0) return a+2*M_PI; else return a;
+}
+
+/*-----------------------------------------*/
+
+static Graph graph_new(struct state *st)
+{
+  Graph new;
+  assert(new = (Graph)calloc(1,sizeof(struct graph)));
+  new->nodes = array_new(100);
+  new->edges = array_new(100);
+  return new;
+}
+
+static void graph_del(Graph g)
+{
+  array_del(g->nodes, &node_del);
+  array_del(g->edges, &edge_del);
+  free(g);
+}
+
+
+static void graph_add_node(Graph g, Node n)
+{
+  array_add_element(g->nodes, n);
+}
+
+static void graph_add_edge(Graph g, Edge e)
+{
+  array_add_element(g->edges, e);
+  
+  /* for each node n of e, add n to pointer e */
+  node_add_edge(e->node1, e);
+  node_add_edge(e->node2, e);
+}
+
+static Edge graph_next_edge_around(Graph g, Node n, Edge e, Direction direction)
+{
+  /* return the next edge after e around node n clockwise */
+  double angle, minangle=20;
+  Edge next_edge = e, edge;
+  int i;
+
+  for (i=0;i<n->edges->nb_elements;i++) {
+    edge=n->edges->elements[i];
+    if (edge != e) {
+      angle = edge_angle_to(e,edge,n,direction);
+      if (angle < minangle) {
+	next_edge=edge;
+	minangle=angle;
+      }
+    }
+  }
+  return next_edge;
+}
+  
+#if 0
+static void graph_to_s(Graph g, FILE *f)
+{
+  int i;
+  for (i=0;i<g->nodes->nb_elements;i++) 
+    node_to_s(g->nodes->elements[i],f);
+  for (i=0;i<g->edges->nb_elements;i++)
+    edge_to_s(g->edges->elements[i],f);
+}
+#endif
+
+static void graph_draw(struct state *st, Graph g)
+{
+  int i;
+  
+  for (i=0;i<g->nodes->nb_elements;i++) 
+    node_draw(st, g->nodes->elements[i]);
+  for (i=0;i<g->edges->nb_elements;i++)
+    edge_draw(st, g->edges->elements[i]);
+}
+
+static void graph_rotate(Graph g, double angle, int cx, int cy)
+{
+  /* rotate all the nodes of the graph around the centre */
+  int i; 
+  float c=cos(angle),s=sin(angle),x,y;
+  Node n;
+  for (i=0;i<g->nodes->nb_elements;i++) {
+    n=g->nodes->elements[i];
+    x=n->x; y=n->y;
+    n->x = (x-cx)*c-(y-cy)*s + cx;
+    n->y = (x-cx)*s+(y-cy)*c + cy;
+  }
+}
+
+
+/*---------------------------*/
+
+static Graph make_polar_graph(struct state *st, 
+                              int xmin, int ymin, int width, int height, 
+		       int nbp, /* number of points on each orbit */
+		       int nbo /* number of orbits */)
+     /* make a simple grid graph, with edges present or absent randomly */
+{
+  int cx = width/2+xmin, cy=height/2+ymin; /* centre */
+  int os = (width<height?width:height)/(2*nbo); /* orbit height */
+  Graph g;
+  Node *grid;
+  int o,p;
+
+  /* generate nodes */
+  assert(grid=(Node*)calloc(1+nbp*nbo,sizeof(Node)));
+  assert(g=graph_new(st));
+  
+  graph_add_node(g, grid[0]=node_new((double)cx,(double)cy));
+
+  for (o=0;o<nbo;o++)
+    for (p=0;p<nbp;p++)
+      graph_add_node(g,
+		     grid[1+o*nbp+p]=node_new(cx+(o+1)*os*sin(p*2*M_PI/nbp), 
+					      cy+(o+1)*os*cos(p*2*M_PI/nbp)));
+
+
+  /* generate edges */
+  for (o=0;o<nbo;o++)
+    for (p=0;p<nbp;p++) {
+      if (o==0) /* link first orbit nodes with centre */
+	graph_add_edge(g,edge_new(grid[1+o*nbp+p],grid[0]));
+      else /* liink orbit nodes with lower orbit */
+      	graph_add_edge(g,edge_new(grid[1+o*nbp+p],grid[1+(o-1)*nbp+p]));
+      /* link along orbit */
+      graph_add_edge(g,edge_new(grid[1+o*nbp+p],
+				grid[1+o*nbp+(p+1)%nbp]));
+    }
+
+  free(grid);
+  return g;
+}
+
+
+static Graph make_grid_graph(struct state *st, 
+                             int xmin, int ymin, int width, int height, int step)
+     /* make a simple grid graph */
+{
+  Graph g;
+  int row,col,x,y;
+  int size=(width<height?height:width);
+
+  /* empirically, it seems there are 2 curves only if both
+     nbcol and nbrow are even, so we round them to even */
+  int nbcol=(2+size/step)/2*2, nbrow=(2+size/step)/2*2;
+
+  Node *grid;
+  assert(grid=(Node*)calloc(nbrow*nbcol,sizeof(Node)));
+  assert(g=graph_new(st));
+
+
+  /* adjust xmin and xmax so that the grid is centered */
+  xmin+=(width-(nbcol-1)*step)/2; 
+  ymin+=(height-(nbrow-1)*step)/2;
+
+  /* create node grid */
+  for (row=0;row<nbrow;row++)
+    for (col=0;col<nbcol;col++) {
+      x=col*step+xmin;
+      y=row*step+ymin;
+      grid[row+col*nbrow]=node_new((double)x, (double)y);
+      graph_add_node(g, grid[row+col*nbrow]);
+    }
+
+  /* create edges */
+  for (row=0;row<nbrow;row++)
+    for (col=0;col<nbcol;col++) {
+      if (col!=nbcol-1)
+	graph_add_edge(g,edge_new(grid[row+col*nbrow],
+				  grid[row+(col+1)*nbrow]));
+      if (row!=nbrow-1)
+	graph_add_edge(g,edge_new(grid[row+col*nbrow],grid[row+1+col*nbrow]));
+      if (col!=nbcol-1 && row!=nbrow-1) {
+	  graph_add_edge(g,edge_new(grid[row+col*nbrow],
+				    grid[row+1+(col+1)*nbrow]));
+	  graph_add_edge(g,edge_new(grid[row+1+col*nbrow],
+				    grid[row+(col+1)*nbrow]));
+      }
+    }
+
+  free(grid);
+  
+  return g;
+}
+
+
+static Graph make_triangle_graph(struct state *st, 
+                                 int xmin, int ymin, int width, int height, int edge_size)
+{
+  Graph g;
+  Node *grid;
+  int row,col;
+  double L=(width<height?width:height)/2.0; /* circumradius of the triangle */
+  double cx=xmin+width/2.0, cy=ymin+height/2.0; /* centre of the triangle */
+  double p2x=cx-L*SQRT_3/2.0, p2y=cy+L/2.0; /* p2 is the bottom left vertex */
+  double x,y;
+  int nsteps=3*L/(SQRT_3*edge_size);
+
+  assert(grid=(Node*)calloc((nsteps+1)*(nsteps+1),sizeof(Node)));
+  assert(g=graph_new(st));
+
+  /* create node grid */
+  for (row=0;row<=nsteps;row++)
+    for (col=0;col<=nsteps;col++) 
+      if (row+col<=nsteps) {
+        x=p2x+col*L*SQRT_3/nsteps + row*L*SQRT_3/(2*nsteps);
+        y=p2y-row*3*L/(2*nsteps);
+        grid[col+row*(nsteps+1)]=node_new((double)x, (double)y);
+        graph_add_node(g, grid[col+row*(nsteps+1)]);
+      }
+
+  /* create edges */
+  for (row=0;row<nsteps;row++)
+    for (col=0;col<nsteps;col++)
+      if (row+col<nsteps) { 
+          /* horizontal edges */
+          graph_add_edge(g,edge_new(grid[row+col*(nsteps+1)],grid[row+(col+1)*(nsteps+1)]));
+          /* vertical edges */
+          graph_add_edge(g,edge_new(grid[row+col*(nsteps+1)],grid[row+1+col*(nsteps+1)]));
+          /* diagonal edges */
+          graph_add_edge(g,edge_new(grid[row+1+col*(nsteps+1)],grid[row+(col+1)*(nsteps+1)]));
+      }
+
+  free(grid);
+  return g;
+  
+}
+
+
+static Graph make_kennicott_graph(struct state *st, 
+                                  int xmin, int ymin, int width, int height, int step,
+                           int cluster_size)
+     /* make a graph inspired by one of the motifs from the Kennicott bible */
+     /* square grid of clusters of the shape  /|\
+      *                                       ---
+      *                                       \|/
+      * cluster_size is the length of an edge of a cluster
+      */
+{
+  Graph g;
+  int row,col,x,y;
+  int size=width<height?height:width;
+  int nbcol=(1+size/step)/2*2, nbrow=(1+size/step)/2*2;
+  Node *grid;
+
+  /* there are 5 nodes by for each cluster */
+  assert(grid=(Node*)calloc(5*nbrow*nbcol,sizeof(Node)));
+  assert(g=graph_new(st));
+
+  /* adjust xmin and xmax so that the grid is centered */
+  xmin+=(width-(nbcol-1)*step)/2; 
+  ymin+=(height-(nbrow-1)*step)/2;
+
+  /* create node grid */
+  for (row=0;row<nbrow;row++)
+    for (col=0;col<nbcol;col++) {
+      int ci=5*(row+col*nbrow);
+      x=col*step+xmin;
+      y=row*step+ymin;
+
+      /* create a cluster centred on x,y */
+      grid[ci  ]=node_new((double)x, (double)y);
+      grid[ci+1]=node_new((double)(x+cluster_size), (double)y);
+      grid[ci+2]=node_new((double)x, (double)(y-cluster_size));
+      grid[ci+3]=node_new((double)(x-cluster_size), (double)y);
+      grid[ci+4]=node_new((double)x, (double)(y+cluster_size));
+
+      graph_add_node(g, grid[ci]);
+      graph_add_node(g, grid[ci+1]);
+      graph_add_node(g, grid[ci+2]);
+      graph_add_node(g, grid[ci+3]);
+      graph_add_node(g, grid[ci+4]);
+
+      /* internal edges */
+      graph_add_edge(g,edge_new(grid[ci], grid[ci+1]));      
+      graph_add_edge(g,edge_new(grid[ci], grid[ci+2]));
+      graph_add_edge(g,edge_new(grid[ci], grid[ci+3]));
+      graph_add_edge(g,edge_new(grid[ci], grid[ci+4]));
+      graph_add_edge(g,edge_new(grid[ci+1], grid[ci+2]));      
+      graph_add_edge(g,edge_new(grid[ci+2], grid[ci+3]));
+      graph_add_edge(g,edge_new(grid[ci+3], grid[ci+4]));
+      graph_add_edge(g,edge_new(grid[ci+4], grid[ci+1]));
+
+    }
+
+  /* create inter-cluster edges */
+  for (row=0;row<nbrow;row++)
+    for (col=0;col<nbcol;col++) {
+      if (col!=nbcol-1)
+        /* horizontal edge from edge 1 of cluster (row, col) to edge 3
+         * of cluster (row,col+1) */
+        graph_add_edge(g,edge_new(grid[5*(row+col*nbrow)+1],grid[5*(row+(col+1)*nbrow)+3]));
+      if (row!=nbrow-1)
+        /* vertical edge from edge 4 of cluster (row, col) to edge 2
+         * of cluster (row+1,col) */
+        graph_add_edge(g,edge_new(grid[5*(row+col*nbrow)+4],
+                                  grid[5*(row+1+col*nbrow)+2]));
+    }
+  free(grid);
+  return g;
+}
+
+/*---------------------------*/
+typedef struct spline_segment {
+  double x1,y1,x2,y2,x3,y3,x4,y4;
+} *SplineSegment;
+
+typedef struct spline {
+  Array segments; /* array of SplineSegment */
+  int color;
+} *Spline;
+
+static Spline spline_new(int color)
+{
+  Spline new=(Spline)calloc(1,sizeof(struct spline));
+  new->segments=array_new(30);
+  new->color=color;
+  return new;
+}
+
+static void spline_del(void *s)
+{
+  array_del(((Spline)s)->segments,&free);
+  free(s);
+}
+
+static void spline_add_segment(Spline s,
+                        double x1, double y1, double x2, double y2, 
+                        double x3, double y3, double x4, double y4)
+{
+  SplineSegment ss=(SplineSegment)calloc(1,sizeof(struct spline_segment));
+  ss->x1=x1;  ss->x2=x2;  ss->x3=x3;  ss->x4=x4;
+  ss->y1=y1;  ss->y2=y2;  ss->y3=y3;  ss->y4=y4;
+  array_add_element(s->segments,ss);
+}
+
+#if 0
+static void spline_to_s(Spline s, FILE *f)
+{
+  int i;
+  SplineSegment ss;
+  fprintf(f,"Spline: \n");
+  for (i=0;i<s->segments->nb_elements;i++) {
+    ss=s->segments->elements[i];
+    fprintf(f," - segment %d: (%g, %g),(%g, %g),(%g, %g),(%g, %g)\n",
+            i,ss->x1,ss->y1,ss->x2,ss->y2,ss->x3,ss->y3,ss->x4,ss->y4);
+  }
+}
+#endif
+
+static void spline_value_at(Spline s, double *x, double *y, double t, int *segment)
+{
+  int si;
+  double tt;
+  SplineSegment ss;
+  si = floor(t*s->segments->nb_elements);
+  tt = t*s->segments->nb_elements - si;
+  assert(tt>=0 && tt<1);
+  ss=s->segments->elements[si];
+
+  *x = ss->x1*(1-tt)*(1-tt)*(1-tt)+3*ss->x2*tt*(1-tt)*(1-tt)+3*ss->x3*tt*tt*(1-tt)+ss->x4*tt*tt*tt;
+  *y = ss->y1*(1-tt)*(1-tt)*(1-tt)+3*ss->y2*tt*(1-tt)*(1-tt)+3*ss->y3*tt*tt*(1-tt)+ss->y4*tt*tt*tt;
+
+  *segment=si;
+}
+
+/*---------------------------*/
+
+static EdgeCouple edge_couple_new(int nb_edges) {
+  int i;
+  EdgeCouple new = (EdgeCouple)calloc(1,sizeof(struct edge_couple));
+  new->array = (int **)calloc(nb_edges, sizeof(int*));
+  new->size = nb_edges;
+
+  for (i=0;i<nb_edges;i++) {
+    new->array[i]=(int *)calloc(2,sizeof(int));
+    new->array[i][CLOCKWISE]=0;
+    new->array[i][ANTICLOCKWISE]=0;
+  }
+  return new;
+}
+
+static void edge_couple_del(EdgeCouple e)
+{
+  int i;
+  for (i=0;i<e->size;i++) free(e->array[i]);
+  free(e->array);
+  free(e);
+}
+    
+/*---------------------------*/
+
+static Pattern pattern_new(struct state *st, Graph g, double shape1, double shape2)
+{
+  Pattern new;
+  assert(new=(Pattern)calloc(1,sizeof(struct pattern)));
+  new->shape1=shape1;
+  new->shape2=shape2;
+  new->graph=g;
+  new->ec=edge_couple_new(g->edges->nb_elements);
+  new->splines=array_new(10);
+  new->ncolors=st->ncolors;
+  return new;
+}
+
+static void pattern_del(Pattern p)
+{
+  edge_couple_del(p->ec);
+  array_del(p->splines,&spline_del);
+  free(p);
+}
+
+static void pattern_edge_couple_set(Pattern p, Edge e, Direction d, int value) 
+{
+  int i;
+  for (i=0;i<p->graph->edges->nb_elements;i++)
+    if (p->graph->edges->elements[i]==e) {
+      p->ec->array[i][d]=value;
+      return;
+    }
+}
+
+static void pattern_draw_spline_direction(Pattern p, Spline s,
+                                   Node node, Edge edge1, Edge edge2, 
+                                   Direction direction)
+{
+  double x1=(edge1->node1->x+edge1->node2->x)/2.0;
+  double y1=(edge1->node1->y+edge1->node2->y)/2.0;
+
+  /* P2 (x2,y2) is the middle point of edge1 */
+  double x4=(edge2->node1->x+edge2->node2->x)/2.0;
+  double y4=(edge2->node1->y+edge2->node2->y)/2.0;
+  
+  double alpha=edge_angle_to(edge1,edge2,node,direction)*p->shape1;
+  double beta=p->shape2;
+  
+  double i1x,i1y,i2x,i2y,x2,y2,x3,y3;
+  
+  if (direction == ANTICLOCKWISE) {
+    /* I1 must stick out to the left of NP1 and I2 to the right of NP4 */
+    i1x =  alpha*(node->y-y1)+x1;
+    i1y = -alpha*(node->x-x1)+y1;
+    i2x = -alpha*(node->y-y4)+x4;
+    i2y =  alpha*(node->x-x4)+y4;
+    x2 =  beta*(y1-i1y) + i1x;
+    y2 = -beta*(x1-i1x) + i1y;
+    x3 = -beta*(y4-i2y) + i2x;
+    y3 =  beta*(x4-i2x) + i2y;
+  }
+  else {
+    /* I1 must stick out to the left of NP1 and I2 to the right of NP4 */
+    i1x = -alpha*(node->y-y1)+x1;
+    i1y =  alpha*(node->x-x1)+y1;
+    i2x =  alpha*(node->y-y4)+x4;
+    i2y = -alpha*(node->x-x4)+y4;
+    x2 = -beta*(y1-i1y) + i1x;
+    y2 =  beta*(x1-i1x) + i1y;
+    x3 =  beta*(y4-i2y) + i2x;
+    y3 = -beta*(x4-i2x) + i2y;
+  }
+
+  spline_add_segment(s,x1,y1,x2,y2,x3,y3,x4,y4);
+}
+
+static int pattern_next_unfilled_couple(Pattern p, Edge *e, Direction *d)
+{
+  int i;
+  for (i=0;i<p->ec->size;i++) {
+    if (p->ec->array[i][CLOCKWISE]==0) {
+      *e=p->graph->edges->elements[i];
+      *d=CLOCKWISE;
+      return 1;
+    }
+    else if (p->ec->array[i][ANTICLOCKWISE]==0) {
+      *e=p->graph->edges->elements[i];
+      *d=ANTICLOCKWISE;
+      return 1;
+    }
+  }
+  return 0;
+}
+
+static void pattern_make_curves(Pattern p)
+{
+  Edge current_edge, first_edge, next_edge;
+  Node current_node, first_node;
+  Direction current_direction, first_direction;
+  Spline s;
+
+  while (pattern_next_unfilled_couple(p, &first_edge, &first_direction)) {
+    /* start a new loop */
+    s=spline_new(random()%(p->ncolors-2)+2);
+    array_add_element(p->splines, s);
+
+    current_edge=first_edge;
+    current_node=first_node=current_edge->node1;
+    current_direction=first_direction;
+
+    do {
+      pattern_edge_couple_set(p, current_edge, current_direction, 1);
+      next_edge = graph_next_edge_around(p->graph,current_node,current_edge,current_direction);
+
+      /* add the spline segment to the spline */
+      pattern_draw_spline_direction(p,s,current_node,
+                                    current_edge,next_edge,current_direction);
+      
+      /* cross the edge */
+      current_edge = next_edge;
+      current_node = edge_other_node(next_edge, current_node);
+      current_direction=1-current_direction;
+
+    } while (current_node!=first_node || current_edge!=first_edge || current_direction!=first_direction);
+
+    if (s->segments->nb_elements==2) /* spline is just one point: remove it */
+      p->splines->elements[p->splines->nb_elements-1]=NULL;
+      
+  }
+}
+
+static void pattern_animate(struct state *st)
+{
+  Pattern p = st->pattern;
+  double t = st->t;
+  double t2;
+  double x,y,x2,y2,x3,y3,x4,y4;
+  int i,segment,unused;
+  int ticks;
+  double step=0.0001; /* TODO: set the step (or the delay) as a
+                        * function of the spline length, so that
+                        * drawing speed is constant
+                        */
+  Spline s;
+
+  XSetLineAttributes(st->dpy,st->gc,st->params.curve_width,LineSolid,CapRound,JoinRound);
+  XSetLineAttributes(st->dpy,st->shadow_gc,st->params.shadow_width,LineSolid,CapRound,JoinRound);
+
+  for (ticks=0;ticks<100 && t<1;ticks++) {
+    for (i=0;i<p->splines->nb_elements;i++) 
+      if ((s=p->splines->elements[i])) { /* skip if one-point spline */
+        spline_value_at(s, &x, &y, fmod(t,1.0),&segment);
+        spline_value_at(s, &x2, &y2, fmod(t+step,1.0),&unused);
+        
+        /* look ahead for the shadow segment */
+        t2=t+step;
+        if (t2<=1.0) {
+          spline_value_at(s, &x3, &y3, fmod(t2,1.0),&unused);
+          while (t2+step<1.0 && (x3-x2)*(x3-x2)+(y3-y2)*(y3-y2) < st->params.shadow_width*st->params.shadow_width) {
+            t2+=step;
+            spline_value_at(s, &x3, &y3, fmod(t2,1.0),&unused);
+          }
+          
+          spline_value_at(s, &x4, &y4, fmod(t2+step,1.0),&unused);
+          
+          /* draw shadow line */
+          XDrawLine(st->dpy,st->window,st->shadow_gc, 
+                    (int)rint(x3),(int)rint(y3), 
+                    (int)rint(x4),(int)rint(y4));
+        } 
+        /* draw line segment */
+        if (p->splines->nb_elements==1)
+          XSetForeground(st->dpy, st->gc, st->colors[segment%(p->ncolors-3)+2].pixel);
+        else
+          XSetForeground(st->dpy, st->gc, st->colors[s->color].pixel);
+        XDrawLine(st->dpy,st->window,st->gc,
+                  (int)rint(x),(int)rint(y),
+                  (int)rint(x2),(int)rint(y2));
+      }
+    t+=step;
+  }
+  st->t=t;
+
+  if (t>=1) {
+    st->reset=1;
+
+    /* at the end we redraw back to remove shadow spillage */
+    for (i=0;i<p->splines->nb_elements;i++) {
+      if ((s=p->splines->elements[i])) {
+	double offset=step;
+	XSetForeground(st->dpy, st->gc, st->colors[s->color].pixel);
+	spline_value_at(s, &x, &y, fmod(t,1.0),&unused);
+
+	spline_value_at(s, &x2, &y2, fmod(t-offset,1.0),&unused);
+      
+	while ((x2-x)*(x2-x)+(y2-y)*(y2-y) < st->params.shadow_width*st->params.shadow_width) {
+	  offset+=step;
+	  spline_value_at(s, &x2, &y2, fmod(t-offset,1.0),&unused);
+	}
+      
+	XDrawLine(st->dpy,st->window,st->gc, (int)rint(x),(int)rint(y), (int)rint(x2),(int)rint(y2));
+      }
+    }
+  }
+}
+
+/*======================================================================*/
+
+static const char *celtic_defaults[] = {
+    ".background: black",
+    ".foreground: #333333",
+    "*fpsSolid:	true",
+    "*ncolors: 20",
+    "*delay: 10000",
+    "*delay2: 5",
+    "*showGraph: False",
+#ifdef HAVE_MOBILE
+    "*ignoreRotation: True",
+#endif
+    0
+};
+
+static XrmOptionDescRec celtic_options[] = {
+    {"-background", ".background", XrmoptionSepArg, 0},
+    {"-foreground", ".foreground", XrmoptionSepArg, 0},
+    {"-ncolors", ".ncolors", XrmoptionSepArg, 0},
+    {"-delay", ".delay", XrmoptionSepArg, 0},
+    {"-delay2", ".delay2", XrmoptionSepArg, 0},
+    {"-graph", ".showGraph", XrmoptionNoArg, "True"},
+    {0, 0, 0, 0}
+};
+
+#if 0
+static void params_to_s(FILE *f)
+{
+  switch (st->params.type) {
+  case polar: fprintf(f,"type: polar\n"); 
+    fprintf(f,"nb_orbits: %ld\n",st->params.nb_orbits);
+    fprintf(f,"nb_nodes_per_orbit: %ld\n",st->params.nb_nodes_per_orbit);
+    break;
+  case tgrid: fprintf(f,"type: grid\n"); 
+    fprintf(f,"edge_size: %ld\n",st->params.edge_size);
+    break;
+  case triangle: fprintf(f,"type: triangle\n"); 
+    fprintf(f,"edge_size: %ld\n",st->params.edge_size);
+    break;
+  case kennicott: 
+    fprintf(f,"type: kennicott\n"); 
+    fprintf(f,"edge_size: %ld\n",st->params.edge_size);
+    fprintf(f,"cluster_size: %ld\n",st->params.cluster_size);
+    break;
+  }
+
+  fprintf(f,"curve width: %ld\n",st->params.curve_width);
+  fprintf(f,"shadow width: %ld\n",st->params.shadow_width);
+  fprintf(f,"shape1: %g\n",st->params.shape1);
+  fprintf(f,"shape2: %g\n",st->params.shape2);
+  fprintf(f,"margin: %ld\n",st->params.margin);
+  fprintf(f,"angle: %g\n",st->params.angle);
+  fprintf(f,"delay: %ld\n",st->params.delay);
+}
+#endif
+
+#if 0
+static void colormap_to_s(int ncolors, XColor *colors)
+{
+  int i;
+  printf("-- colormap (%d colors):\n",st->ncolors);
+  for (i=0;i<st->ncolors;i++)
+    printf("%d: %d %d %d\n", i, st->colors[i].red, st->colors[i].green, st->colors[i].blue);
+  printf("----\n");
+}
+#endif
+
+
+static void *
+celtic_init (Display *d_arg, Window w_arg)
+{
+  struct state *st = (struct state *) calloc (1, sizeof(*st));
+  XGCValues gcv;
+
+  st->dpy=d_arg; st->window=w_arg;
+  st->showGraph=get_boolean_resource (st->dpy, "showGraph", "Boolean");
+
+  st->ncolors = get_integer_resource (st->dpy, "ncolors", "Integer");
+
+
+  XGetWindowAttributes (st->dpy, st->window, &st->xgwa);
+  assert(st->colors = (XColor *) calloc (st->ncolors,sizeof(XColor)));
+
+  if (get_boolean_resource(st->dpy, "mono", "Boolean"))
+    {
+    MONO:
+      st->ncolors = 1;
+      st->colors[0].pixel = get_pixel_resource(st->dpy, st->xgwa.colormap,
+                                           "foreground", "Foreground");
+    }
+  else
+    {
+#if 0
+      make_random_colormap (st->xgwa.screen, st->xgwa.visual, st->xgwa.colormap,
+                            st->colors, &st->ncolors, True, True, 0, True);
+#else
+      make_smooth_colormap (st->xgwa.screen, st->xgwa.visual, st->xgwa.colormap,
+                            st->colors, &st->ncolors, True, 0, True);
+#endif
+      if (st->ncolors < 2)
+        goto MONO;
+      else {
+	st->colors[0].pixel = get_pixel_resource(st->dpy, st->xgwa.colormap,
+                                             "foreground", "Foreground");
+	st->colors[1].pixel = get_pixel_resource(st->dpy, st->xgwa.colormap,
+                                             "background", "Background");
+      }
+    }
+  
+  
+  /* graphic context for curves */
+  gcv.foreground = st->colors[0].pixel;
+  gcv.background = st->colors[1].pixel;
+  gcv.line_width = st->params.curve_width;
+  gcv.cap_style=CapRound;
+  st->gc = XCreateGC (st->dpy, st->window, GCForeground|GCBackground|GCLineWidth|GCCapStyle, &gcv);
+  
+  /* graphic context for graphs */
+  gcv.foreground = st->colors[0].pixel;
+  gcv.background = st->colors[1].pixel;
+  st->gc_graph = XCreateGC (st->dpy, st->window, GCForeground|GCBackground, &gcv);
+  
+  /* graphic context for shadows */
+  gcv.foreground = st->colors[1].pixel;
+  gcv.line_width = st->params.shadow_width;
+  gcv.cap_style=CapRound;
+  st->shadow_gc = XCreateGC(st->dpy, st->window, GCForeground|GCLineWidth|GCCapStyle, &gcv);
+
+  st->delay2 = 1000000 * get_integer_resource(st->dpy, "delay2", "Delay2");
+
+  return st;
+}
+
+static unsigned long
+celtic_draw (Display *dpy, Window window, void *closure)
+{
+  struct state *st = (struct state *) closure;
+
+  if (st->eraser) {
+    st->eraser = erase_window (st->dpy, st->window, st->eraser);
+    return 10000;
+  }
+
+  if (st->reset || st->force_reset) {
+    int delay = (st->force_reset ? 0 : st->delay2);
+    st->reset = 0;
+    st->force_reset = 0;
+    st->t = 1;
+
+    if (st->pattern != NULL) {
+      pattern_del(st->pattern);
+    }
+    st->pattern = NULL;
+    graph_del(st->graph);
+
+    /* recolor each time */
+    st->ncolors = get_integer_resource (st->dpy, "ncolors", "Integer");
+    if (st->ncolors > 2)
+      make_smooth_colormap (st->xgwa.screen, st->xgwa.visual, st->xgwa.colormap,
+                            st->colors, &st->ncolors, True, 0, True);
+
+    st->eraser = erase_window (st->dpy, st->window, st->eraser);
+    return (delay);
+  }
+
+  if (st->pattern == NULL) {
+    st->params.curve_width=random()%5+4;
+    st->params.shadow_width=st->params.curve_width+4;
+    st->params.shape1=(15+random()%15)/10.0 -1.0;
+    st->params.shape2=(15+random()%15)/10.0 -1.0;
+    st->params.edge_size=10*(random()%5)+20;
+    st->params.delay=get_integer_resource(st->dpy, "delay", "Delay");
+    st->params.angle=random()%360*2*M_PI/360;
+    st->params.margin=(random()%8)*100-600;
+
+    switch (random()%4) {
+    case 0:
+      st->params.type=tgrid;
+      st->params.shape1=(random()%1*2-1.0)*(random()%10+3)/10.0;
+      st->params.shape2=(random()%1*2-1.0)*(random()%10+3)/10.0;
+      st->params.edge_size=10*(random()%5)+50;
+      break;
+    case 1:
+      st->params.type=kennicott;
+      st->params.shape1=(random()%20)/10.0 -1.0;
+      st->params.shape2=(random()%20)/10.0 -1.0;
+      st->params.edge_size=10*(random()%3)+70;
+      st->params.cluster_size=st->params.edge_size/(3.0+random()%10)-1;
+      break;
+    case 2:
+      st->params.type=triangle;
+      st->params.edge_size=10*(random()%5)+60;
+      st->params.margin=(random()%10)*100-900;
+      break;
+    case 3:
+      st->params.type=polar;
+      st->params.nb_orbits=2+random()%10;
+      st->params.nb_nodes_per_orbit=4+random()%10;
+      break;
+    }
+
+
+/*     st->params.type= polar; */
+/*   st->params.nb_orbits= 5; */
+/*   st->params.nb_nodes_per_orbit= 19; */
+/*   st->params.curve_width= 4; */
+/*   st->params.shadow_width= 8; */
+/*   st->params.shape1= 0.5; */
+/*   st->params.shape2= 1.3; */
+/*   st->params.margin= 30; */
+/*   st->params.angle= 5.21853; */
+/*   st->params.delay= 10000; */
+
+    
+/*     params_to_s(stdout); */
+    
+  /*=======================================================*/
+    
+    
+    switch (st->params.type) {
+    case tgrid:
+      st->graph=make_grid_graph(st, st->params.margin,st->params.margin,
+                        st->xgwa.width-2*st->params.margin, 
+			st->xgwa.height-2*st->params.margin, 
+			st->params.edge_size);
+      break;
+    case kennicott:
+      st->graph=make_kennicott_graph(st, st->params.margin,st->params.margin,
+			     st->xgwa.width-2*st->params.margin, 
+			     st->xgwa.height-2*st->params.margin, 
+			     st->params.edge_size,
+			     st->params.cluster_size);
+      break;
+    case triangle:
+      st->graph=make_triangle_graph(st, st->params.margin,st->params.margin,
+                            st->xgwa.width-2*st->params.margin, 
+                            st->xgwa.height-2*st->params.margin, 
+                            st->params.edge_size);
+      break;
+    case polar:
+      st->graph=make_polar_graph(st, st->params.margin,st->params.margin,
+                         st->xgwa.width-2*st->params.margin, 
+                         st->xgwa.height-2*st->params.margin, 
+                         st->params.nb_nodes_per_orbit, 
+                         st->params.nb_orbits);
+      break;
+    default:
+      st->graph=make_grid_graph(st, st->params.margin,st->params.margin,
+                        st->xgwa.width-2*st->params.margin, 
+                        st->xgwa.height-2*st->params.margin, 
+                        st->params.edge_size);
+      break;
+    }
+
+    graph_rotate(st->graph,st->params.angle,st->xgwa.width/2,st->xgwa.height/2);
+    
+    if (st->showGraph)
+      graph_draw(st, st->graph);
+    
+    st->pattern=pattern_new(st, st->graph, st->params.shape1, st->params.shape2);
+    pattern_make_curves(st->pattern);
+    st->t = 0.0;
+  }
+
+  pattern_animate(st);
+
+  return st->params.delay;
+}
+
+
+static void
+celtic_reshape (Display *dpy, Window window, void *closure, 
+                 unsigned int w, unsigned int h)
+{
+  struct state *st = (struct state *) closure;
+  XGetWindowAttributes (st->dpy, st->window, &st->xgwa);
+}
+
+static Bool
+celtic_event (Display *dpy, Window window, void *closure, XEvent *event)
+{
+  struct state *st = (struct state *) closure;
+  if (screenhack_event_helper (dpy, window, event))
+    {
+      st->force_reset = 1;
+      return True;
+    }
+  return False;
+}
+
+static void
+celtic_free (Display *dpy, Window window, void *closure)
+{
+  struct state *st = (struct state *) closure;
+  free (st);
+}
+
+
+XSCREENSAVER_MODULE ("Celtic", celtic)
-- 
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