Add an equal length constraint for line segments.

[git-p4: depot-paths = "//depot/solvespace/": change = 1680]

constraint.cpp

@@ -49,6 +49,18 @@ void Constraint::MenuConstrain(int id) {
             AddConstraint(&c);
             break;
 
+        case GraphicsWindow::MNU_EQUAL:
+            if(gs.lineSegments == 2 && gs.n == 2) {
+                c.type = EQUAL_LENGTH_LINES;
+                c.entityA = gs.entity[0];
+                c.entityB = gs.entity[1];
+            } else {
+                Error("Bad selection for equal length / radius constraint.");
+                return;
+            }
+            AddConstraint(&c);
+            break;
+
         case GraphicsWindow::MNU_SOLVE_NOW:
             SS.Solve();
             return;
@@ -104,6 +116,14 @@ void Constraint::Generate(IdList<Equation,hEquation> *l) {
             AddEq(l, Distance(ptA, ptB)->Minus(exprA), 0);
             break;
 
+        case EQUAL_LENGTH_LINES: {
+            Entity *a = SS.GetEntity(entityA);
+            Entity *b = SS.GetEntity(entityB);
+            AddEq(l, Distance(a->assoc[0], a->assoc[1])->Minus(
+                     Distance(b->assoc[0], b->assoc[1])), 0);
+            break;
+        }
+
         case POINTS_COINCIDENT: {
             Expr *ax, *ay, *az;
             Expr *bx, *by, *bz;

drawconstraint.cpp

@@ -98,6 +98,20 @@ void Constraint::DrawOrGetDistance(Vector *labelPos) {
             break;
         }
 
+        case EQUAL_LENGTH_LINES: {
+            for(int i = 0; i < 2; i++) {
+                Entity *e = SS.GetEntity(i == 0 ? entityA : entityB);
+                Vector a = SS.GetEntity(e->assoc[0])->PointGetCoords();
+                Vector b = SS.GetEntity(e->assoc[1])->PointGetCoords();
+                Vector m = (a.ScaledBy(1.0/3)).Plus(b.ScaledBy(2.0/3));
+                Vector ab = a.Minus(b);
+                Vector n = (gn.Cross(ab)).WithMagnitude(10/SS.GW.scale);
+                
+                LineDrawOrGetDistance(m.Minus(n), m.Plus(n));
+            }
+            break;
+        }
+
         default: oops();
     }
 }

dsc.h

@@ -54,6 +54,8 @@ public:
     Point2d ScaledBy(double s);
     double DistanceTo(Point2d p);
     double DistanceToLine(Point2d p0, Point2d dp, bool segment);
+    double Magnitude(void);
+    Point2d WithMagnitude(double v);
 };
 
 template <class T, class H>

graphicswin.cpp

@@ -70,7 +70,7 @@ const GraphicsWindow::MenuEntry GraphicsWindow::menu[] = {
 { 1, "&Vertical\tShift+V",                  0,                  'V'|S,  NULL  },
 { 1, NULL,                                  0,                          NULL  },
 { 1, "&On Point / Curve / Plane\tShift+O",  MNU_ON_ENTITY,      'O'|S,  mCon  },
-{ 1, "E&qual Length / Radius\tShift+Q",     0,                  'Q'|S,  NULL  },
+{ 1, "E&qual Length / Radius\tShift+Q",     MNU_EQUAL,          'Q'|S,  mCon  },
 { 1, "At &Midpoint\tShift+M",               0,                  'M'|S,  NULL  },
 { 1, "S&ymmetric\tShift+Y",                 0,                  'Y'|S,  NULL  },
 { 1, NULL,                                  0,                          NULL  },

sketch.h

@@ -213,9 +213,10 @@ public:
     static const int PT_PT_DISTANCE     = 30;
     static const int PT_LINE_DISTANCE   = 31;
     static const int PT_IN_PLANE        = 40;
+    static const int EQUAL_LENGTH_LINES = 50;
 
-    static const int HORIZONTAL         = 40;
-    static const int VERTICAL           = 41;
+    static const int HORIZONTAL         = 80;
+    static const int VERTICAL           = 81;
 
     int         tag;
     hConstraint h;

ui.h

@@ -96,6 +96,7 @@ public:
         MNU_LINE_SEGMENT,
         // Constrain
         MNU_DISTANCE_DIA,
+        MNU_EQUAL,
         MNU_ON_ENTITY,
         MNU_SOLVE_NOW,
     } MenuId;

util.cpp

@@ -248,6 +248,20 @@ Point2d Point2d::ScaledBy(double s) {
     return r;
 }
 
+double Point2d::Magnitude(void) {
+    return sqrt(x*x + y*y);
+}
+
+Point2d Point2d::WithMagnitude(double v) {
+    double m = Magnitude();
+    if(m < 0.001) {
+        Point2d r = { v, 0 };
+        return r;
+    } else {
+        return ScaledBy(v/Magnitude());
+    }
+}
+
 double Point2d::DistanceTo(Point2d p) {
     double dx = x - p.x;
     double dy = y - p.y;