Skip creating an automatic H/V constraint if it would be redundant.

This means that automatically added H/V constraints now will never
cause the sketch to become overconstrained, which currently makes
that feature almost unusable.

CHANGELOG.md

@@ -37,6 +37,8 @@ New constraint features:
     Values are edited in the configured unit regardless of label format.
   * It is now possible to turn off automatic creation of horizontal/vertical
     constraints on line segments.
+  * Automatic creation of constraints no longer happens if the constraint
+    would have been redundant with other ones.
 
 New export/import features:
   * Three.js: allow configuring projection for exported model, and initially

src/constraint.cpp

@@ -75,10 +75,6 @@ void Constraint::DeleteAllConstraintsFor(Constraint::Type type, hEntity entityA,
     SS.GW.hover.Clear();
 }
 
-hConstraint Constraint::AddConstraint(Constraint *c) {
-    return AddConstraint(c, /*rememberForUndo=*/true);
-}
-
 hConstraint Constraint::AddConstraint(Constraint *c, bool rememberForUndo) {
     if(rememberForUndo) SS.UndoRemember();
 
@@ -107,8 +103,17 @@ hConstraint Constraint::Constrain(Constraint::Type type, hEntity ptA, hEntity pt
     return AddConstraint(&c, /*rememberForUndo=*/false);
 }
 
-hConstraint Constraint::Constrain(Constraint::Type type, hEntity ptA, hEntity ptB, hEntity entityA){
+hConstraint Constraint::TryConstrain(Constraint::Type type, hEntity ptA, hEntity ptB,
-    return Constrain(type, ptA, ptB, entityA, Entity::NO_ENTITY, /*other=*/false, /*other2=*/false);
+                                     hEntity entityA, hEntity entityB,
+                                     bool other, bool other2) {
+    SolveResult solvedBefore = SS.TestRankForGroup(SS.GW.activeGroup);
+    hConstraint hc = Constrain(type, ptA, ptB, entityA, entityB, other, other2);
+    SolveResult solvedAfter = SS.TestRankForGroup(SS.GW.activeGroup);
+    if(solvedBefore == SolveResult::OKAY && solvedAfter == SolveResult::REDUNDANT_OKAY) {
+        SK.constraint.RemoveById(hc);
+        hc = {};
+    }
+    return hc;
 }
 
 hConstraint Constraint::ConstrainCoincident(hEntity ptA, hEntity ptB) {

src/mouse.cpp

@@ -526,7 +526,7 @@ void GraphicsWindow::MouseRightUp(double x, double y) {
     if(context.active) return;
 
     if(pending.operation == Pending::DRAGGING_NEW_LINE_POINT && pending.hasSuggestion) {
-        Constraint::Constrain(SS.GW.pending.suggestion,
+        Constraint::TryConstrain(SS.GW.pending.suggestion,
             Entity::NO_ENTITY, Entity::NO_ENTITY, pending.request.entity(0));
     }
 
@@ -943,7 +943,8 @@ void GraphicsWindow::MouseLeftDown(double mx, double my) {
     }
 
     // This will be clobbered by MouseMoved below.
-    bool hasConstraintSuggestion = SS.GW.pending.hasSuggestion;
+    bool hasConstraintSuggestion = pending.hasSuggestion;
+    Constraint::Type constraintSuggestion = pending.suggestion;
 
     // Make sure the hover is up to date.
     MouseMoved(mx, my, /*leftDown=*/false, /*middleDown=*/false, /*rightDown=*/false,
@@ -1223,12 +1224,6 @@ void GraphicsWindow::MouseLeftDown(double mx, double my) {
         }
 
         case Pending::DRAGGING_NEW_LINE_POINT: {
-            // Constrain the line segment horizontal or vertical if close enough
-            if(hasConstraintSuggestion) {
-                Constraint::Constrain(SS.GW.pending.suggestion,
-                    Entity::NO_ENTITY, Entity::NO_ENTITY, pending.request.entity(0));
-            }
-
             if(hover.entity.v) {
                 Entity *e = SK.GetEntity(hover.entity);
                 if(e->IsPoint()) {
@@ -1246,7 +1241,15 @@ void GraphicsWindow::MouseLeftDown(double mx, double my) {
                 }
             }
 
-            if(ConstrainPointByHovered(pending.point, &mouse)) {
+            bool doneDragging = ConstrainPointByHovered(pending.point, &mouse);
+
+            // Constrain the line segment horizontal or vertical if close enough
+            if(hasConstraintSuggestion) {
+                Constraint::TryConstrain(constraintSuggestion,
+                    Entity::NO_ENTITY, Entity::NO_ENTITY, pending.request.entity(0));
+            }
+
+            if(doneDragging) {
                 ClearPending();
                 break;
             }

src/sketch.h

@@ -727,16 +727,17 @@ public:
 
     std::string DescriptionString() const;
 
-    static hConstraint AddConstraint(Constraint *c, bool rememberForUndo);
+    static hConstraint AddConstraint(Constraint *c, bool rememberForUndo = true);
-    static hConstraint AddConstraint(Constraint *c);
     static void MenuConstrain(Command id);
     static void DeleteAllConstraintsFor(Constraint::Type type, hEntity entityA, hEntity ptA);
 
     static hConstraint ConstrainCoincident(hEntity ptA, hEntity ptB);
-    static hConstraint Constrain(Constraint::Type type, hEntity ptA, hEntity ptB, hEntity entityA);
+    static hConstraint Constrain(Constraint::Type type, hEntity ptA, hEntity ptB, hEntity entityA,
-    static hConstraint Constrain(Constraint::Type type, hEntity ptA, hEntity ptB,
+                                 hEntity entityB = Entity::NO_ENTITY, bool other = false,
-                                    hEntity entityA, hEntity entityB,
+                                 bool other2 = false);
-                                    bool other, bool other2);
+    static hConstraint TryConstrain(Constraint::Type type, hEntity ptA, hEntity ptB,
+                                    hEntity entityA, hEntity entityB = Entity::NO_ENTITY,
+                                    bool other = false, bool other2 = false);
 };
 
 class hEquation {