From: Ben Harris <bjh21@bjh21.me.uk>
Date: Mon, 17 Jul 2017 23:14:20 +0000 (+0100)
Subject: Further cleanup of skeleton paths.
X-Git-Tag: bedstead-002.000~126
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~bjharris/git?a=commitdiff_plain;h=c56e10dc09b538589ad4e8ca4a9bbf42f39089fe;p=bedstead.git

Further cleanup of skeleton paths.

The cleanup itself is good, but emit_paths() will need enhancement.
At the moment, it assumes that all paths are closed, so it doesn't
matter where on a path it starts emitting it.  With an open path,
though, it's important to emit it starting at one end, so there will
have to be a mechanism for distinguishing open from closed paths and
behaving accordingly.
---

diff --git a/bedstead.c b/bedstead.c
index f47f521..8499a66 100644
--- a/bedstead.c
+++ b/bedstead.c
@@ -1898,10 +1898,34 @@ dochar(char const data[YSIZE], unsigned flags)
 	emit_path();
 }
 
+static void
+reverse_path(point *a)
+{
+	point *tmp;
+	
+	while (a->prev != NULL)
+		a = a->prev;
+	while (a != NULL) {
+		tmp = a->next;
+		a->next = a->prev;
+		a->prev = tmp;
+		a = tmp;
+	}
+}		
+
 /* Join together two points each at the end of a path */
 static void
 join_ends(point *a, point *b)
 {
+	point *tmp;
+
+	if (a->prev == NULL && b->next == NULL) {
+		tmp = a; a = b; b = tmp;
+	}
+	if (a->prev == NULL)
+		reverse_path(a);
+	if (b->next == NULL)
+		reverse_path(b);
 	assert(a->next == NULL);
 	assert(a->prev != NULL);
 	assert(b->prev == NULL);
@@ -1910,7 +1934,7 @@ join_ends(point *a, point *b)
 	a->next = b;
 	b->prev = a;
 	fix_identical(a); /* Will delete a */
-	fix_collinear(b); /* Will delete b */
+	fix_collinear(b); /* Might delete b */
 }
 
 static bool
@@ -1919,23 +1943,44 @@ point_endp(point *p)
 	return p->next == NULL || p->prev == NULL;
 }
 
+static bool
+point_deadp(point *p)
+{
+	return p->next == NULL && p->prev == NULL;
+}
+
 static void
 clean_skeleton()
 {
 	int i, j;
 
+	/* Pass 1: join collinear connected segments */
 	for (i = 0; i < nextpoint; i++) {
-		if (points[i].prev == NULL && points[i].next == NULL)
+		if (point_deadp(&points[i]))
 			continue;
 		for (j = 0; j < nextpoint; j++) {
-			if (points[j].prev == NULL && points[j].next == NULL)
+			if (point_deadp(&points[j]))
 				continue;
 			if (vec_eqp(points[i].v, points[j].v) &&
 			    points[i].next == NULL && points[j].prev == NULL &&
 			    vec_inline3(points[i].prev->v, points[i].v,
 					points[j].next->v))
 				join_ends(&points[i], &points[j]);
-			if (points[i].prev == NULL && points[i].next == NULL)
+			if (point_deadp(&points[i]))
+				break;
+		}
+	}
+	/* Pass 2: join any connected segments */
+	for (i = 0; i < nextpoint; i++) {
+		if (point_deadp(&points[i]))
+			continue;
+		for (j = i+1; j < nextpoint; j++) {
+			if (point_deadp(&points[j]))
+				continue;
+			if (vec_eqp(points[i].v, points[j].v) &&
+			    point_endp(&points[i]) && point_endp(&points[j]))
+				join_ends(&points[i], &points[j]);
+			if (point_deadp(&points[i]))
 				break;
 		}
 	}