From 97adbc28c05505d96f541de0c5c709a1865a70ac Mon Sep 17 00:00:00 2001
From: Zeno Rogue <zeno@attnam.com>
Date: Wed, 27 Nov 2019 21:08:09 +0100
Subject: [PATCH] Euclidean distance restored

---
 cell.cpp   | 16 +++++-----------
 euclid.cpp | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+), 11 deletions(-)

diff --git a/cell.cpp b/cell.cpp
index 59dabc5d..a66f4501 100644
--- a/cell.cpp
+++ b/cell.cpp
@@ -417,16 +417,6 @@ EX void verifycells(heptagon *at) {
   verifycell(at->c7);
   }
 
-EX int eudist(int sx, int sy) {
-  int z0 = abs(sx);
-  int z1 = abs(sy);
-  if(a4 && BITRUNCATED)
-    return (z0 == z1 && z0 > 0) ? z0+1: max(z0, z1);
-  if(a4) return z0 + z1;
-  int z2 = abs(sx+sy);
-  return max(max(z0,z1), z2);
-  }
-
 EX int compdist(int dx[]) {
   int mi = dx[0];
   for(int u=0; u<S3; u++) mi = min(mi, dx[u]);
@@ -454,7 +444,7 @@ EX int celldist(cell *c) {
     return d;
     }
   if(nil && !quotient) return DISTANCE_UNKNOWN;
-  if(euclid && (penrose || archimedean)) return celldistance(currentmap->gamestart(), c);
+  if(euclid) return celldistance(currentmap->gamestart(), c);
   if(sphere || binarytiling || WDIM == 3 || cryst || solnih || penrose) return celldistance(currentmap->gamestart(), c);
   #if CAP_IRR
   if(IRREGULAR) return irr::celldist(c, false);
@@ -1026,6 +1016,10 @@ EX int celldistance(cell *c1, cell *c2) {
   if(cryst) return crystal::precise_distance(c1, c2);
   #endif
   
+  if(euclid && WDIM == 2) {
+    return cyldist(euc2_coordinates(c1), euc2_coordinates(c2));
+    }
+
   if(archimedean || quotient || solnih || (penrose && euclid) || experimental || sl2 || nil) {
     
     if(saved_distances.count(make_pair(c1,c2)))
diff --git a/euclid.cpp b/euclid.cpp
index ea6d5ae0..f4113c06 100644
--- a/euclid.cpp
+++ b/euclid.cpp
@@ -901,4 +901,50 @@ EX bool chiral(gp::loc g) {
 
 EX euclid3::coord first_period() { return 0; }
 
+EX void twist_once(gp::loc coo) {
+  coo = coo - euclid3::twisted_vec * gp::univ_param();
+  if(euclid3::twisted&8) {
+    gp::loc ort = (S3 == 3 ? gp::loc(1, -2) : gp::loc(0, 1)) * euclid3::twisted_vec * gp::univ_param();
+    auto s = ort * dscalar(coo, ort) * 2;
+    auto v = dscalar(ort, ort);
+    s.first /= v;
+    s.second /= v;
+    coo = coo - s;
+    }
+  }
+
+EX int eudist(int sx, int sy, bool reduce IS(true)) {
+  int z0 = abs(sx);
+  int z1 = abs(sy);
+  if(a4 && BITRUNCATED)
+    return (z0 == z1 && z0 > 0 && reduce) ? z0+1: max(z0, z1);
+  if(a4) return z0 + z1;
+  int z2 = abs(sx+sy);
+  return max(max(z0,z1), z2);
+  }
+
+EX int eudist(gp::loc a, gp::loc b) {
+  return eudist(a.first-b.first, a.second-b.second, (a.first ^ a.second)&1);
+  }
+
+EX int cyldist(gp::loc a, gp::loc b) {
+  a = as_gp(euclid3::getcoord(euclid3::canonicalize(as_coord(a))));
+  b = as_gp(euclid3::getcoord(euclid3::canonicalize(as_coord(b))));
+  
+  if(!quotient) return eudist(a, b);
+  
+  int best = 0;
+  for(int sa=0; sa<16; sa++) {
+    auto _a = a, _b = b;
+    if(sa&1) twist_once(_a);
+    if(sa&2) twist_once(_b);
+    if(sa&4) _a = _a + euclid3::ortho_vec * gp::univ_param();
+    if(sa&8) _b = _b + euclid3::ortho_vec * gp::univ_param();
+    int val = eudist(_a, _b);
+    if(sa == 0 || val < best) best = val;
+    }
+  
+  return best;
+  }
+
 }