--- a/svghmi/gen_index_xhtml.ysl2	Mon Mar 16 17:09:23 2020 +0100
+++ b/svghmi/gen_index_xhtml.ysl2	Mon Mar 16 18:27:49 2020 +0100
@@ -85,114 +85,7 @@
         }
     }
 
-    def "func:intersect_1d" {
-        // it is assumed that a1 > a0 and b1 > b0
-        param "a0";
-        param "a1";
-        param "b0";
-        param "b1";
-
-        const "d0", "$a0 >= $b0";
-        const "d1", "$a1 >= $b1";
-        choose {
-            when "not($d0) and $d1"
-                // b contained in a
-                //   a0<b0 b1<a1
-                // a +--------+
-                // b    +--+
-                result "3";
-            when "$d0 and not($d1)"
-                // a contained in b
-                //   b0<a0 a1<b1
-                // a    +--+
-                // b +--------+
-                result "2";
-            when "$d0 and $d1 and $a0 < $b1"
-                // a and b are overlapped 
-                //   b0<a0<b1<a1
-                // a    +-----+
-                // b +-----+
-                result "1";
-            when "not($d0) and not($d1) and $b0 < $a1"
-                // a and b are overlapped
-                //   a0<b0<a1<b1
-                // a +-----+
-                // b    +-----+
-                result "1";
-            otherwise
-                result "0"; /* no intersection*/
-        }
-    }
-
-    // returns :
-    // 0 - no intersection
-    //            .-----.
-    //    .-----. |    b|
-    //    |     | |     |
-    //    |     | '-----'
-    //    |a    |
-    //    '-----'
-    //
-    // 1 - overlapping
-    //        .-----.
-    //    .---|--. b|
-    //    |   |  |  |
-    //    |   '-----'
-    //    |a     |
-    //    '------'
-    //
-    // 2 - overlapping
-    //        .-----.
-    //        |  a  |
-    //    .---|-----|---.
-    //    |   '-----'   |
-    //    | b           |
-    //    '-------------'
-    //
-    // 3 - overlapping
-    //        .-----.
-    //        |  b  |
-    //    .---|-----|---.
-    //    |   '-----'   |
-    //    | a           |
-    //    '-------------'
-    //
-    // 4 - a contained in b
-    //    .-------------.
-    //    |   .-----.   |
-    //    |   |  a  |   |
-    //    |b  '-----'   |
-    //    '-------------'
-    //
-    // 6 - overlapping
-    //        .----.
-    //        |   b|
-    //    .---|----|---.
-    //    |a  |    |   |
-    //    '---|----|---'
-    //        '----'
-    //
-    // 9 - b contained in a
-    //    .-------------.
-    //    |   .-----.   |
-    //    |   |  b  |   |
-    //    |a  '-----'   |
-    //    '-------------'
-    //
-    def "func:intersect" {
-        param "a";
-        param "b";
-
-        const "x_intersect", "func:intersect_1d($a/@x, $a/@x+$a/@w, $b/@x, $b/@x+$b/@w)";
-
-        choose{
-            when "$x_intersect != 0"{
-                const "y_intersect", "func:intersect_1d($a/@y, $a/@y+$a/@h, $b/@y, $b/@y+$b/@h)";
-                result "$x_intersect * $y_intersect";
-            }
-            otherwise result "0";
-        }
-    }
+    include bbox_intersect.ysl2
 
     // return overlapping geometry for a given element
     // all intersercting element are returned