arrows: refactor arrow generating functions to return the actual start point

This is currently a no-op, but upcoming commits will adjust the arrow
start point to take pendwidth into account in order to avoid
overlapping the node periphery and subsequent primitive arrow shapes
of multi-shape arrows.

The arrow start point is the point on the arrow which is farthest away
along the edge from the node it is associated with.

Towards https://gitlab.com/graphviz/graphviz/-/issues/372.

diff --git a/lib/common/arrows.c b/lib/common/arrows.c
index 515a35c1b67aeecf30dd043da59aa2755df58070..29284fbc39f2197bef888015a7783c02e3aa9656 100644 (file)
--- a/lib/common/arrows.c
+++ b/lib/common/arrows.c
@@ -107,18 +107,18 @@ static arrowname_t Arrownames[] = {
 typedef struct arrowtype_t {
     int type;
     double lenfact;            /* ratio of length of this arrow type to standard arrow */
-    void (*gen) (GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);        /* generator function for type */
+    pointf (*gen) (GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);      /* generator function for type */
 } arrowtype_t;
 
 /* forward declaration of functions used in Arrowtypes[] */
-static void arrow_type_normal(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
-static void arrow_type_crow(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
-static void arrow_type_tee(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
-static void arrow_type_box(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
-static void arrow_type_diamond(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
-static void arrow_type_dot(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
-static void arrow_type_curve(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
-static void arrow_type_gap(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
+static pointf arrow_type_normal(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
+static pointf arrow_type_crow(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
+static pointf arrow_type_tee(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
+static pointf arrow_type_box(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
+static pointf arrow_type_diamond(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
+static pointf arrow_type_dot(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
+static pointf arrow_type_curve(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
+static pointf arrow_type_gap(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
 
 static const arrowtype_t Arrowtypes[] = {
     {ARR_TYPE_NORM, 1.0, arrow_type_normal},
@@ -424,7 +424,7 @@ void arrowOrthoClip(edge_t* e, pointf* ps, int startp, int endp, bezier* spl, in
     }
 }
 
-static void arrow_type_normal(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
+static pointf arrow_type_normal(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
 {
     (void)arrowsize;
 
@@ -460,9 +460,11 @@ static void arrow_type_normal(GVJ_t * job, pointf p, pointf u, double arrowsize,
        gvrender_polygon(job, &a[2], 3, !(flag & ARR_MOD_OPEN));
     else
        gvrender_polygon(job, &a[1], 3, !(flag & ARR_MOD_OPEN));
+
+    return q;
 }
 
-static void arrow_type_crow(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
+static pointf arrow_type_crow(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
 {
     pointf m, q, v, w, a[9];
     double arrowwidth, shaftwidth;
@@ -520,9 +522,11 @@ static void arrow_type_crow(GVJ_t * job, pointf p, pointf u, double arrowsize, d
        gvrender_polygon(job, &a[3], 6, 1);
     else
        gvrender_polygon(job, a, 9, 1);
+
+    return q;
 }
 
-static void arrow_type_gap(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
+static pointf arrow_type_gap(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
 {
     (void)arrowsize;
     (void)penwidth;
@@ -535,9 +539,11 @@ static void arrow_type_gap(GVJ_t * job, pointf p, pointf u, double arrowsize, do
     a[0] = p;
     a[1] = q;
     gvrender_polyline(job, a, 2);
+
+    return q;
 }
 
-static void arrow_type_tee(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
+static pointf arrow_type_tee(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
 {
     (void)arrowsize;
     (void)penwidth;
@@ -571,9 +577,11 @@ static void arrow_type_tee(GVJ_t * job, pointf p, pointf u, double arrowsize, do
     a[0] = p;
     a[1] = q;
     gvrender_polyline(job, a, 2);
+
+    return q;
 }
 
-static void arrow_type_box(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
+static pointf arrow_type_box(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
 {
     (void)arrowsize;
     (void)penwidth;
@@ -605,9 +613,11 @@ static void arrow_type_box(GVJ_t * job, pointf p, pointf u, double arrowsize, do
     a[0] = m;
     a[1] = q;
     gvrender_polyline(job, a, 2);
+
+    return q;
 }
 
-static void arrow_type_diamond(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
+static pointf arrow_type_diamond(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
 {
     (void)arrowsize;
     (void)penwidth;
@@ -632,9 +642,11 @@ static void arrow_type_diamond(GVJ_t * job, pointf p, pointf u, double arrowsize
        gvrender_polygon(job, a, 3, !(flag & ARR_MOD_OPEN));
     else
        gvrender_polygon(job, a, 4, !(flag & ARR_MOD_OPEN));
+
+    return q;
 }
 
-static void arrow_type_dot(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
+static pointf arrow_type_dot(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
 {
     (void)arrowsize;
     (void)penwidth;
@@ -648,13 +660,17 @@ static void arrow_type_dot(GVJ_t * job, pointf p, pointf u, double arrowsize, do
     AF[1].x = p.x + u.x / 2. + r;
     AF[1].y = p.y + u.y / 2. + r;
     gvrender_ellipse(job, AF, !(flag & ARR_MOD_OPEN));
+
+    const pointf q = {p.x + u.x, p.y + u.y};
+
+    return q;
 }
 
 
 /* Draw a concave semicircle using a single cubic bezier curve that touches p at its midpoint.
  * See http://digerati-illuminatus.blogspot.com.au/2008/05/approximating-semicircle-with-cubic.html for details.
  */
-static void arrow_type_curve(GVJ_t* job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
+static pointf arrow_type_curve(GVJ_t* job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
 {
     (void)arrowsize;
 
@@ -698,6 +714,8 @@ static void arrow_type_curve(GVJ_t* job, pointf p, pointf u, double arrowsize, d
     else if (flag & ARR_MOD_RIGHT)
        Bezier(AF, 3, 0.5, AF, NULL);
     gvrender_beziercurve(job, AF, sizeof(AF) / sizeof(pointf), FALSE, FALSE, FALSE);
+
+    return q;
 }
 
 
@@ -711,9 +729,7 @@ static pointf arrow_gen_type(GVJ_t * job, pointf p, pointf u, double arrowsize,
        if (f == arrowtype->type) {
            u.x *= arrowtype->lenfact * arrowsize;
            u.y *= arrowtype->lenfact * arrowsize;
-           (arrowtype->gen) (job, p, u, arrowsize, penwidth, flag);
-           p.x = p.x + u.x;
-           p.y = p.y + u.y;
+           p = (arrowtype->gen) (job, p, u, arrowsize, penwidth, flag);
            break;
        }
     }