add support for central connection circle after arrow in lifeline direction

on-behalf-of: @Mermaid-Chart <hello@mermaidchart.com>

packages/mermaid/src/diagrams/sequence/parser/sequenceDiagram.jison

@@ -73,7 +73,7 @@ accDescr\s*"{"\s*                                { this.begin("acc_descr_multili
 "off"															return 'off';
 ","                                                             return ',';
 ";"                                                             return 'NEWLINE';
-[^\/\\\+\<->\->:\n,;]+((?!(\-x|\-\-x|\-\)|\-\-\)|\-\|\\|\-\\|\-\/|\-\/\/|\-\|\/|\/\|\-|\\\|\-|\/\/\-|\\\\\-|\/\|\-|\-\-\|\\|\-\-))[\-]*[^\+\<->\->:\n,;]+)*             { yytext = yytext.trim(); return 'ACTOR'; } //final_4.11
+[^\/\\\+\()\<->\->:\n,;]+((?!(\-x|\-\-x|\-\)|\-\-\)|\-\|\\|\-\\|\-\/|\-\/\/|\-\|\/|\/\|\-|\\\|\-|\/\/\-|\\\\\-|\/\|\-|\-\-\|\\|\-\-|\(\)))[\-]*[^\+\<->\->:\n,;]+)*             { yytext = yytext.trim(); return 'ACTOR'; } //final_4.11
 "->>"                                                           return 'SOLID_ARROW';
 "<<->>"                                                           return 'BIDIRECTIONAL_SOLID_ARROW';
 "-->>"                                                          return 'DOTTED_ARROW';
@@ -113,6 +113,7 @@ accDescr\s*"{"\s*                                { this.begin("acc_descr_multili
 ":"                             								return 'TXT';
 "+"                                                             return '+';
 "-"                                                             return '-';
+"()"                                                            return '()';
 <<EOF>>                                                         return 'NEWLINE';
 .                                                               return 'INVALID';
 
@@ -322,6 +323,20 @@ signal
 	{ $$ = [$1,$4,{type: 'addMessage', from:$1.actor, to:$4.actor, signalType:$2, msg:$5},
 	             {type: 'activeEnd', signalType: yy.LINETYPE.ACTIVE_END, actor: $1.actor}
 	             ]}
+    | actor signaltype '()' actor text2
+	{ $$ = [$1,$4,{type: 'addMessage', from:$1.actor, to:$4.actor, signalType:$2, msg:$5, activate: true, centralConnection: yy.LINETYPE.CENTRAL_CONNECTION},
+	              {type: 'centralConnection', signalType: yy.LINETYPE.CENTRAL_CONNECTION, actor: $4.actor, }
+	             ]}
+    
+	| actor '()' signaltype actor text2
+	{ $$ = [$1,$4,{type: 'addMessage', from:$1.actor, to:$4.actor, signalType:$3, msg:$5, activate: false, centralConnection: yy.LINETYPE.CENTRAL_CONNECTION_REVERSE},
+	              {type: 'centralConnectionReverse', signalType: yy.LINETYPE.CENTRAL_CONNECTION_REVERSE, actor: $1.actor}
+	             ]}
+	| actor '()' signaltype '()' actor text2
+	{ $$ = [$1,$5,{type: 'addMessage', from:$1.actor, to:$5.actor, signalType:$3, msg:$6, activate: true, centralConnection: yy.LINETYPE.CENTRAL_CONNECTION_DUAL},
+	 			 {type: 'centralConnection', signalType: yy.LINETYPE.CENTRAL_CONNECTION, actor: $5.actor, },
+				 {type: 'centralConnectionReverse', signalType: yy.LINETYPE.CENTRAL_CONNECTION_REVERSE, actor: $1.actor}
+	             ]}
 	| actor signaltype actor text2
 	{ $$ = [$1,$3,{type: 'addMessage', from:$1.actor, to:$3.actor, signalType:$2, msg:$4}]}
 	;

packages/mermaid/src/diagrams/sequence/sequenceDb.ts

@@ -82,6 +82,10 @@ const LINETYPE = {
   SOLID_ARROW_BOTTOM_REVERSE_DOTTED: 56,
   STICK_ARROW_TOP_REVERSE_DOTTED: 57,
   STICK_ARROW_BOTTOM_REVERSE_DOTTED: 58,
+
+  CENTRAL_CONNECTION: 59,
+  CENTRAL_CONNECTION_REVERSE: 60,
+  CENTRAL_CONNECTION_DUAL: 61,
 } as const;
 
 const ARROWTYPE = {
@@ -238,7 +242,8 @@ export class SequenceDB implements DiagramDB {
     idTo?: Message['to'],
     message?: { text: string; wrap: boolean },
     messageType?: number,
-    activate = false
+    activate = false,
+    centralConnection?: number
   ) {
     if (messageType === this.LINETYPE.ACTIVE_END) {
       const cnt = this.activationCount(idFrom ?? '');
@@ -265,6 +270,7 @@ export class SequenceDB implements DiagramDB {
       wrap: message?.wrap ?? this.autoWrap(),
       type: messageType,
       activate,
+      centralConnection,
     });
     return true;
   }
@@ -557,6 +563,12 @@ export class SequenceDB implements DiagramDB {
         case 'activeStart':
           this.addSignal(param.actor, undefined, undefined, param.signalType);
           break;
+        case 'centralConnection':
+          this.addSignal(param.actor, undefined, undefined, param.signalType);
+          break;
+        case 'centralConnectionReverse':
+          this.addSignal(param.actor, undefined, undefined, param.signalType);
+          break;
         case 'activeEnd':
           this.addSignal(param.actor, undefined, undefined, param.signalType);
           break;
@@ -600,7 +612,14 @@ export class SequenceDB implements DiagramDB {
               this.state.records.lastDestroyed = undefined;
             }
           }
-          this.addSignal(param.from, param.to, param.msg, param.signalType, param.activate);
+          this.addSignal(
+            param.from,
+            param.to,
+            param.msg,
+            param.signalType,
+            param.activate,
+            param.centralConnection
+          );
           break;
         case 'boxStart':
           this.addBox(param.boxData);

packages/mermaid/src/diagrams/sequence/sequenceRenderer.ts

@@ -281,6 +281,36 @@ const drawNote = async function (elem: any, noteModel: NoteModel) {
   bounds.models.addNote(noteModel);
 };
 
+const drawCentralConnection = function (
+  elem: any,
+  msg: any,
+  msgModel: any,
+  diagObj: Diagram,
+  startx,
+  stopx,
+  lineStartY
+) {
+  const g = elem.append('g');
+  const circle = g.append('circle');
+  circle.attr(
+    'cx',
+    msg.centralConnection === diagObj.db.LINETYPE.CENTRAL_CONNECTION ? stopx + 7.5 : startx - 5
+  );
+  // circle.attr('cx',x);
+  circle.attr('cy', lineStartY);
+  circle.attr('r', 5);
+  circle.attr('width', 10);
+  circle.attr('height', 10);
+  if (msg.centralConnection === diagObj.db.LINETYPE.CENTRAL_CONNECTION_DUAL) {
+    const circle = g.append('circle');
+    circle.attr('cx', stopx + 7.5);
+    circle.attr('cy', lineStartY);
+    circle.attr('r', 5);
+    circle.attr('width', 10);
+    circle.attr('height', 10);
+  }
+};
+
 const messageFont = (cnf) => {
   return {
     fontFamily: cnf.messageFontFamily,
@@ -366,7 +396,7 @@ async function boundMessage(_diagram, msgModel): Promise<number> {
  * @param lineStartY - The Y coordinate at which the message line starts
  * @param diagObj - The diagram object.
  */
-const drawMessage = async function (diagram, msgModel, lineStartY: number, diagObj: Diagram) {
+const drawMessage = async function (diagram, msgModel, lineStartY: number, diagObj: Diagram, msg) {
   const { startx, stopx, starty, message, type, sequenceIndex, sequenceVisible } = msgModel;
   const textDims = utils.calculateTextDimensions(message, messageFont(conf));
   const textObj = svgDrawCommon.getTextObj();
@@ -432,6 +462,9 @@ const drawMessage = async function (diagram, msgModel, lineStartY: number, diagO
     line.attr('y1', lineStartY);
     line.attr('x2', stopx);
     line.attr('y2', lineStartY);
+    if (msg.centralConnection) {
+      drawCentralConnection(diagram, msg, msgModel, diagObj, startx, stopx, lineStartY);
+    }
   }
   // Make an SVG Container
   // Draw the line
@@ -921,6 +954,12 @@ export const draw = async function (_text: string, id: string, _version: string,
       case diagObj.db.LINETYPE.ACTIVE_START:
         bounds.newActivation(msg, diagram, actors);
         break;
+      case diagObj.db.LINETYPE.CENTRAL_CONNECTION:
+        bounds.newActivation(msg, diagram, actors);
+        break;
+      case diagObj.db.LINETYPE.CENTRAL_CONNECTION_REVERSE:
+        bounds.newActivation(msg, diagram, actors);
+        break;
       case diagObj.db.LINETYPE.ACTIVE_END:
         activeEnd(msg, bounds.getVerticalPos());
         break;
@@ -1079,7 +1118,7 @@ export const draw = async function (_text: string, id: string, _version: string,
             createdActors,
             destroyedActors
           );
-          messagesToDraw.push({ messageModel: msgModel, lineStartY: lineStartY });
+          messagesToDraw.push({ messageModel: msgModel, lineStartY: lineStartY, msg });
           bounds.models.addMessage(msgModel);
         } catch (e) {
           log.error('error while drawing message', e);
@@ -1132,7 +1171,7 @@ export const draw = async function (_text: string, id: string, _version: string,
   await drawActors(diagram, actors, actorKeys, false);
 
   for (const e of messagesToDraw) {
-    await drawMessage(diagram, e.messageModel, e.lineStartY, diagObj);
+    await drawMessage(diagram, e.messageModel, e.lineStartY, diagObj, e.msg);
   }
   if (conf.mirrorActors) {
     await drawActors(diagram, actors, actorKeys, true);
@@ -1546,6 +1585,12 @@ const buildMessageModel = function (msg, actors, diagObj) {
   let startx = isArrowToRight ? fromRight : fromLeft;
   let stopx = isArrowToRight ? toLeft : toRight;
 
+  if (
+    msg.centralConnection === diagObj.db.LINETYPE.CENTRAL_CONNECTION_REVERSE ||
+    msg.centralConnection === diagObj.db.LINETYPE.CENTRAL_CONNECTION_DUAL
+  ) {
+    startx += 4;
+  }
   // As the line width is considered, the left and right values will be off by 2.
   const isArrowToActivation = Math.abs(toLeft - toRight) > 2;
 

packages/mermaid/src/diagrams/sequence/types.ts

@@ -35,6 +35,7 @@ export interface Message {
   type?: number;
   activate?: boolean;
   placement?: string;
+  centralConnection?: number;
 }
 
 export interface AddMessageParams {
@@ -50,6 +51,8 @@ export interface AddMessageParams {
     | 'destroyParticipant'
     | 'activeStart'
     | 'activeEnd'
+    | 'centralConnection'
+    | 'centralConnectionReverse'
     | 'addNote'
     | 'addLinks'
     | 'addALink'