Draw an additional projection line, when showing a point-line

projected distance constraint.

[git-p4: depot-paths = "//depot/solvespace/": change = 1712]

drawconstraint.cpp

@@ -151,6 +151,19 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
             LineDrawOrGetDistance(pt, closest);
             Vector ref = ((closest.Plus(pt)).ScaledBy(0.5)).Plus(disp.offset);
             DoLabel(ref, labelPos, gr, gu);
+
+            if(workplane.v != Entity::FREE_IN_3D.v) {
+                // Draw the projection marker from the closest point on the
+                // projected line to the projected point on the real line.
+                lAB = (lA.Minus(lB));
+                double t = (lA.Minus(closest)).DivPivoting(lAB);
+
+                Vector lA = SS.GetEntity(line->point[0])->PointGetNum();
+                Vector lB = SS.GetEntity(line->point[1])->PointGetNum();
+
+                Vector c2 = (lA.ScaledBy(1-t)).Plus(lB.ScaledBy(t));
+                DoProjectedPoint(&c2);
+            }
             break;
         }
 

dsc.h

@@ -48,6 +48,7 @@ public:
     Vector WithMagnitude(double s);
     Vector ScaledBy(double s);
     Vector ProjectInto(hEntity wrkpl);
+    double DivPivoting(Vector delta);
 };
 
 class Point2d {

util.cpp

@@ -275,6 +275,18 @@ Vector Vector::ProjectInto(hEntity wrkpl) {
     return p0.Plus((u.ScaledBy(up)).Plus(v.ScaledBy(vp)));
 }
 
+double Vector::DivPivoting(Vector delta) {
+    double m = max(fabs(delta.x), max(fabs(delta.y), fabs(delta.z)));
+
+    if(m == fabs(delta.x)) {
+        return x/delta.x;
+    } else if(m == fabs(delta.y)) {
+        return y/delta.y;
+    } else if(m == fabs(delta.z)) {
+        return z/delta.z;
+    } else oops();
+}
+
 Point2d Point2d::Plus(Point2d b) {
     Point2d r;
     r.x = x + b.x;