From d6e18114eb95ed3affb9cf670ea08454dceffc2c Mon Sep 17 00:00:00 2001
From: azv <azv@opencascade.com>
Date: Thu, 5 Mar 2020 11:07:37 +0300
Subject: [PATCH] 0031407: [Regression to 7.3.0] Extrema does not process
 parallel circles correctly

Use correct ranges of circles when processing the concentric case. Repeat the range comparison 3 times shifting each time for a half-period to process the extrema between boundary points of arcs.
---
 src/Extrema/Extrema_ExtCC.cxx  | 12 +++++++-----
 tests/bugs/modalg_7/bug31407_1 | 13 +++++++++++++
 tests/bugs/modalg_7/bug31407_2 | 13 +++++++++++++
 tests/bugs/modalg_7/bug31407_3 | 20 ++++++++++++++++++++
 4 files changed, 53 insertions(+), 5 deletions(-)
 create mode 100644 tests/bugs/modalg_7/bug31407_1
 create mode 100644 tests/bugs/modalg_7/bug31407_2
 create mode 100644 tests/bugs/modalg_7/bug31407_3

diff --git a/src/Extrema/Extrema_ExtCC.cxx b/src/Extrema/Extrema_ExtCC.cxx
index ed7dd90104..7e23dab0e6 100644
--- a/src/Extrema/Extrema_ExtCC.cxx
+++ b/src/Extrema/Extrema_ExtCC.cxx
@@ -553,7 +553,7 @@ void Extrema_ExtCC::PrepareParallelResult(const Standard_Real theUt11,
       if ((aRange.Delta() > Precision::Angular()) &&
           ((aPar2 - aPar1) < Precision::Angular()))
       {
-        aPar1 -= aPeriod;
+        aPar2 += aPeriod;
       }
     }
 
@@ -562,11 +562,13 @@ void Extrema_ExtCC::PrepareParallelResult(const Standard_Real theUt11,
 
     Standard_Real aMinSquareDist = RealLast();
 
-    aProjRng1.Add(aPar1 - M_PI);
-    aProjRng1.Add(aPar2 - M_PI);
-    for (Standard_Integer i = 0; i < 2; i++)
+    aProjRng1.Add(aPar1 - aPeriod);
+    aProjRng1.Add(aPar2 - aPeriod);
+    for (Standard_Integer i = 0; i < 3; i++)
     {
-      // Repeat computation twice
+      // Repeat computation three times, shifting the range to PI on each step,
+      // to be able to find if the concentric arcs ranges are intersected in just one parameter
+      // (lower or upper boundary).
 
       Bnd_Range aRng = aProjRng1;
       aRng.Common(aRange);
diff --git a/tests/bugs/modalg_7/bug31407_1 b/tests/bugs/modalg_7/bug31407_1
new file mode 100644
index 0000000000..a6a01642c0
--- /dev/null
+++ b/tests/bugs/modalg_7/bug31407_1
@@ -0,0 +1,13 @@
+puts "========"
+puts "0031407: Extrema does not process parallel circles correctly"
+puts "========"
+puts ""
+
+circle c1  0 0 0  0 0 1  5
+circle c2  0 0 0  0 0 1  10
+
+if { [regexp "Infinite number of extremas" [extrema c1 c2]] == 1} {
+  puts "OK : Circles are treated as concentric"
+} else {
+  puts "Error : Extrema does not find the circles are parallel"
+}
diff --git a/tests/bugs/modalg_7/bug31407_2 b/tests/bugs/modalg_7/bug31407_2
new file mode 100644
index 0000000000..4f569fbd57
--- /dev/null
+++ b/tests/bugs/modalg_7/bug31407_2
@@ -0,0 +1,13 @@
+puts "========"
+puts "0031407: Extrema does not process parallel circles correctly"
+puts "========"
+puts ""
+
+circle c1  0 0 0  0 0 -1  5
+circle c2  0 0 0  0 0 1  10
+
+if { [regexp "Infinite number of extremas" [extrema c1 c2]] == 1} {
+  puts "OK : Circles are treated as concentric"
+} else {
+  puts "Error : Extrema does not find the circles are parallel"
+}
diff --git a/tests/bugs/modalg_7/bug31407_3 b/tests/bugs/modalg_7/bug31407_3
new file mode 100644
index 0000000000..dbe0e1942d
--- /dev/null
+++ b/tests/bugs/modalg_7/bug31407_3
@@ -0,0 +1,20 @@
+puts "========"
+puts "0031407: Extrema does not process parallel circles correctly"
+puts "========"
+puts ""
+
+circle c1  0 0 0  0 0 1  5
+circle c2  0 0 0  0 0 1  10
+
+trim cc1 c1 0 2
+trim cc2 c2 2 4
+
+set res_extrema [extrema cc1 cc2]
+
+if { [regexp "Infinite number of extremas" $res_extrema] == 0} {
+  if {[llength $res_extrema] != 1} {
+    puts "Error : expected 1 extrema, but found [llength $res_extrema]"
+  }
+} else {
+  puts "Error : Infinite number of extremas is found"
+}