Add support for direction statement

packages/mermaid/src/diagrams/requirement/parser/requirementDiagram.jison

@@ -22,6 +22,10 @@ accDescr\s*":"\s*                                               { this.begin("ac
 accDescr\s*"{"\s*                                { this.begin("acc_descr_multiline");}
 <acc_descr_multiline>[\}]                       { this.popState(); }
 <acc_descr_multiline>[^\}]*                     return "acc_descr_multiline_value";
+.*direction\s+TB[^\n]*                       return 'direction_tb';
+.*direction\s+BT[^\n]*                       return 'direction_bt';
+.*direction\s+RL[^\n]*                       return 'direction_rl';
+.*direction\s+LR[^\n]*                       return 'direction_lr';
 (\r?\n)+                               return 'NEWLINE';
 \s+                                    /* skip all whitespace */
 \#[^\n]*                               /* skip comments */
@@ -101,8 +105,20 @@ diagram
   | elementDef diagram
   | relationshipDef diagram
   | directive diagram
+  | direction diagram
   | NEWLINE diagram;
 
+direction
+    : direction_tb
+    { yy.setDirection('TB');}
+    | direction_bt
+    { yy.setDirection('BT');}
+    | direction_rl
+    { yy.setDirection('RL');}
+    | direction_lr
+    { yy.setDirection('LR');}
+    ;
+
 requirementDef
   : requirementType requirementName STRUCT_START NEWLINE requirementBody
     { yy.addRequirement($2, $1) };

packages/mermaid/src/diagrams/requirement/requirementDb.ts

@@ -53,6 +53,12 @@ const Relationships = {
   TRACES: 'traces',
 };
 
+let direction = 'TB';
+const getDirection = () => direction;
+const setDirection = (dir: string) => {
+  direction = dir;
+};
+
 const getInitialRequirement = (): Requirement => ({
   id: '',
   text: '',
@@ -215,7 +221,7 @@ const getData = () => {
     counter++;
   }
 
-  return { nodes, edges, other: {}, config };
+  return { nodes, edges, other: {}, config, direction: getDirection() };
 };
 
 export default {
@@ -236,6 +242,8 @@ export default {
   getAccDescription,
   setDiagramTitle,
   getDiagramTitle,
+  getDirection,
+  setDirection,
   addElement,
   getElements,
   setNewElementType,