From 4a34253a37e9b79e67818859032815798bbfbaa3 Mon Sep 17 00:00:00 2001
From: phkahler <14852918+phkahler@users.noreply.github.com>
Date: Mon, 16 Jan 2023 13:35:09 -0500
Subject: [PATCH] Don't try to drag points with pt-coincident constraint to a
 previous group. Fixes #1012 and makes dragging as done in one of the
 tutorials possible again.

---
 src/drawentity.cpp | 40 ++++++++++++++++++++++++++++++++--------
 src/sketch.h       |  2 +-
 2 files changed, 33 insertions(+), 9 deletions(-)

diff --git a/src/drawentity.cpp b/src/drawentity.cpp
index d0092544..2dbbe541 100644
--- a/src/drawentity.cpp
+++ b/src/drawentity.cpp
@@ -180,19 +180,43 @@ bool Entity::IsVisible() const {
     return true;
 }
 
+static bool PtCanDrag(hEntity pt) {
+    Entity* p = SK.GetEntity(pt);
+    // a numeric copy can not move
+    if(p->type == Entity::Type::POINT_N_COPY) return false;
+    // these transforms applied zero times can not be moved
+    if(((p->type == Entity::Type::POINT_N_TRANS) ||
+       (p->type == Entity::Type::POINT_N_ROT_AA) ||
+       (p->type == Entity::Type::POINT_N_ROT_AXIS_TRANS))
+        && (p->timesApplied == 0)) return false;
+    return true;
+}
+
 // entities that were created via some copy types will not be
 // draggable with the mouse. We identify the undraggables here
 bool Entity::CanBeDragged() const {
-    // a numeric copy can not move
-    if(type == Entity::Type::POINT_N_COPY) return false;
-    // these transforms applied zero times can not be moved
-    if(((type == Entity::Type::POINT_N_TRANS) ||
-       (type == Entity::Type::POINT_N_ROT_AA) ||
-       (type == Entity::Type::POINT_N_ROT_AXIS_TRANS))
-        && (timesApplied == 0)) return false;
+    if(IsPoint()) {
+        if(!PtCanDrag(h))
+            return false;
+        // are we constrained pt-on-point from a previous group?
+        for(const Constraint &cc : SK.constraint) {
+            if(cc.group == group && cc.type == ConstraintBase::Type::POINTS_COINCIDENT) {
+                if(cc.ptA == h) {
+                    if((SK.GetEntity(cc.ptB)->group < group)
+                      || (!PtCanDrag(cc.ptB)))
+                      return false;
+                }
+                if(cc.ptB == h) {
+                    if((SK.GetEntity(cc.ptA)->group < group)
+                      || (!PtCanDrag(cc.ptA)))
+                      return false;
+                }
+            }
+        }
+    }
     // for these types of entities the first point will indicate draggability
     if(HasEndpoints() || type == Entity::Type::CIRCLE) {
-        return SK.GetEntity(point[0])->CanBeDragged();
+        return PtCanDrag(point[0]);
     }
     // if we're not certain it can't be dragged then default to true
     return true;
diff --git a/src/sketch.h b/src/sketch.h
index 33853d96..020f4081 100644
--- a/src/sketch.h
+++ b/src/sketch.h
@@ -576,7 +576,7 @@ public:
     bool IsStylable() const;
     bool IsVisible() const;
     bool CanBeDragged() const;
-
+    
     enum class DrawAs { DEFAULT, OVERLAY, HIDDEN, HOVERED, SELECTED };
     void Draw(DrawAs how, Canvas *canvas);
     void GetReferencePoints(std::vector<Vector> *refs);