From a37457ead99f2d5c5baca79405d1abe8da8b1cbe Mon Sep 17 00:00:00 2001
From: Zeno Rogue <zeno@attnam.com>
Date: Thu, 2 Jan 2020 16:51:32 +0100
Subject: [PATCH] precise_width for nicer long lines

---
 config.cpp | 16 +++++++++++++++-
 graph.cpp  | 13 +++++++++++--
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/config.cpp b/config.cpp
index 0deb3a68..8eb91fc0 100644
--- a/config.cpp
+++ b/config.cpp
@@ -296,6 +296,7 @@ EX void initConfig() {
   addsaver(vid.usingGL, "usingGL", true);
   addsaver(vid.antialias, "antialias", AA_NOGL | AA_FONT | (ISWEB ? AA_MULTI : AA_LINES) | AA_LINEWIDTH | AA_VERSION);
   addsaver(vid.linewidth, "linewidth", 1);
+  addsaver(precise_width, "precisewidth", .5);
   addsaver(linepatterns::width, "pattern-linewidth", 1);
   addsaver(vid.scale, "scale", 1);
   addsaver(vid.xposition, "xposition", 0);
@@ -1115,7 +1116,20 @@ EX void showGraphConfig() {
       dialog::editNumber(vid.linewidth, 0, 10, 0.1, 1, XLAT("line width"), "");
       dialog::extra_options = [] () {
         dialog::addBoolItem("finer lines at the boundary", vid.antialias & AA_LINEWIDTH, 'O');
-        dialog::add_action([] () { vid.antialias ^= AA_LINEWIDTH; });
+        dialog::add_action([] () { 
+          vid.antialias ^= AA_LINEWIDTH; 
+          });
+
+        if(vid.antialias & AA_LINEWIDTH) {
+          dialog::addSelItem("variable width", fts(precise_width), 'M');
+          dialog::add_action([] () {
+            popScreen();
+            dialog::editNumber(precise_width, 0, 2, 0.1, 0.5, 
+              XLAT("variable width"), XLAT("lines longer than this value will be split into shorter lines, with width computed separately for each of them.")
+              );
+            });
+          }
+        else dialog::addBreak(100);
         
         dialog::addBoolItem("standard graphics", neon_mode == 0, 'A');
         dialog::add_action([] { neon_mode = 0; });
diff --git a/graph.cpp b/graph.cpp
index 12818100..3724eb79 100644
--- a/graph.cpp
+++ b/graph.cpp
@@ -3588,9 +3588,18 @@ bool celldrawer::cell_clipped() {
   return false;
   }
 
+EX ld precise_width = .5;
+
 EX void gridline(const transmatrix& V1, const hyperpoint h1, const transmatrix& V2, const hyperpoint h2, color_t col, int prec) {
-  ld d = hdist(h1, h2);
-  while(d > .5 && d < 100) d /= 2, prec++;
+  ld d = hdist(V1*h1, V2*h2);
+  println(hlog, "d = ", d);
+  while(d > precise_width && d < 100) { 
+    if(!eqmatrix(V1, V2, 1e-6)) { gridline(V1, h1, V1, inverse(V1) * V2 * h2, col, prec); return; }
+    hyperpoint h = midz(h1, h2); 
+    gridline(V1, h1, V1, h, col, prec); 
+    gridline(V1, h, V1, h2, col, prec); 
+    return;
+    }
 #if MAXMDIM >= 4
   if(WDIM == 2 && GDIM == 3) {
     ld eps = cgi.human_height/100;