PreBarrage: sort graph nodes to prevent lines crossings

src/app/components/pb-schema/pb-schema.component.ts

@@ -266,6 +266,12 @@ export class PbSchemaComponent implements AfterViewInit, AfterContentInit, OnIni
                 // store, to draw later
                 sortedWalls.push(c);
             }
+            this.existingWalls[basinsPair]++;
+            // draw wall Node
+            def.push(`${c.uid}["${this.itemDesription(c)}"]`); // square edges
+            def.push(`class ${c.uid} wall;`);
+            // draw "arrow" with 2 lines
+            def.push(`${upstreamBasinId}---${c.uid}-->${downstreamBasinId}`);
         }
         // sort then draw walls
         sortedWalls.sort(this.triCloisonsGaucheDroite);