6638:sequence diagram additional messages

.changeset/loud-results-melt.md

@@ -0,0 +1,5 @@
+---
+'mermaid': minor
+---
+
+feat: Add half-arrowheads (solid & stick) and central connection support

cypress/integration/rendering/sequencediagram-v2.spec.js

@@ -655,5 +655,126 @@ describe('Sequence Diagram Special Cases', () => {
         expect(svg).to.not.have.attr('style');
       });
     });
+
+    describe('Central Connection Rendering Tests', () => {
+      it('should render central connection circles on actor vertical lines', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        Alice ()->>() Bob: Central connection
+        Bob ()-->> Charlie: Reverse central connection
+        Charlie ()<<-->>() Alice: Dual central connection`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with different arrow types', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()->>() Bob: Solid open arrow
+        Alice ()-->>() Bob: Dotted open arrow
+        Alice ()-x() Bob: Solid cross
+        Alice ()--x() Bob: Dotted cross
+        Alice ()->() Bob: Solid arrow`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with bidirectional arrows', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        Alice ()<<->>() Bob: Bidirectional solid
+        Alice ()<<-->>() Bob: Bidirectional dotted`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with activations', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        Alice ()->>() Bob: Activate Bob
+        activate Bob
+        Bob ()-->> Charlie: Message to Charlie
+        Bob ()->>() Alice: Response to Alice
+        deactivate Bob`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections mixed with normal messages', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        Alice ->> Bob: Normal message
+        Bob ()->>() Charlie: Central connection
+        Charlie -->> Alice: Normal dotted message
+        Alice ()<<-->>() Bob: Dual central connection
+        Bob -x Charlie: Normal cross message`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with notes', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        Alice ()->>() Bob: Central connection
+        Note over Alice,Bob: Central connection note
+        Bob ()-->> Charlie: Reverse central connection
+        Note right of Charlie: Response note
+        Charlie ()<<-->>() Alice: Dual central connection`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with loops and alternatives', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+        participant Alice
+        participant Bob
+        participant Charlie
+        loop Every minute
+            Alice ()->>() Bob: Central heartbeat
+            Bob ()-->> Charlie: Forward heartbeat
+        end
+        alt Success
+            Charlie ()<<-->>() Alice: Success response
+        else Failure
+            Charlie ()-x() Alice: Failure response
+        end`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render central connections with different participant types', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+          participant Alice
+          actor Bob
+          participant Charlie@{"type":"boundary"}
+          participant David@{"type":"control"}
+          participant Eve@{"type":"entity"}
+          Alice ()->>() Bob: To actor
+          Bob ()-->> Charlie: To boundary
+          Charlie ()->>() David: To control
+          David ()<<-->>() Eve: To entity
+          Eve ()-x() Alice: Back to participant`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+    });
   });
 });

cypress/integration/rendering/sequencediagram.spec.js

@@ -1053,4 +1053,167 @@ describe('Sequence diagram', () => {
       ]);
     });
   });
+  describe('render new arrow type', () => {
+    it('should render Solid half arrow top', () => {
+      imgSnapshotTest(
+        `
+    sequenceDiagram
+      Alice -|\\  John: Hello John, how are you? 
+      Alice-|\\  John: Hi Alice, I can hear you!
+      Alice -|\\  John: Test
+      `
+      );
+    });
+    it('should render Solid half arrow bottom', () => {
+      imgSnapshotTest(
+        `
+    sequenceDiagram
+      Alice-|/John: Hello John, how are you?
+      Alice-|/John: Hi Alice, I can hear you!
+      Alice-|/John: Test
+      `
+      );
+    });
+
+    it('should render Stick half arrow top ', () => {
+      imgSnapshotTest(
+        `
+     sequenceDiagram
+      Alice-\\\\John: Hello John, how are you?
+      Alice-\\\\John: Hi Alice, I can hear you!
+      Alice-\\\\John: Test
+      `
+      );
+    });
+    it('should render Stick half arrow bottom ', () => {
+      imgSnapshotTest(
+        `
+       sequenceDiagram
+      Alice-//John: Hello John, how are you?
+      Alice-//John: Hi Alice, I can hear you!
+      Alice-//John: Test
+      `
+      );
+    });
+    it('should render Solid half arrow top reverse ', () => {
+      imgSnapshotTest(
+        `
+       sequenceDiagram
+      Alice/|-John: Hello Alice, how are you?
+      Alice/|-John: Hi Alice, I can hear you!
+      Alice/|-John: Test
+
+      `
+      );
+    });
+
+    it('should render Solid half arrow bottom reverse ', () => {
+      imgSnapshotTest(
+        `sequenceDiagram
+        Alice \\|- John: Hello Alice, how are you?
+        Alice \\|- John: Hi Alice, I can hear you!
+        Alice \\|- John: Test`
+      );
+    });
+
+    it('should render Stick half arrow top reverse ', () => {
+      imgSnapshotTest(
+        `
+      sequenceDiagram
+      Alice //-John: Hello Alice, how are you?
+      Alice //-John: Hi Alice, I can hear you!
+      Alice //-John: Test`
+      );
+    });
+
+    it('should render Stick half arrow bottom reverse ', () => {
+      imgSnapshotTest(
+        `
+       sequenceDiagram
+      Alice \\\\-John: Hello Alice, how are you?
+      Alice \\\\-John: Hi Alice, I can hear you!
+      Alice \\\\-John: Test`
+      );
+    });
+
+    it('should render Solid half arrow top dotted', () => {
+      imgSnapshotTest(
+        `
+     sequenceDiagram
+      Alice --|\\John: Hello John, how are you?
+      Alice --|\\John: Hi Alice, I can hear you!
+      Alice --|\\John: Test`
+      );
+    });
+
+    it('should render Solid half arrow bottom dotted', () => {
+      imgSnapshotTest(
+        `
+     sequenceDiagram
+      Alice --|/John: Hello John, how are you?
+      Alice --|/John: Hi Alice, I can hear you!
+      Alice --|/John: Test`
+      );
+    });
+
+    it('should render Stick half arrow top dotted', () => {
+      imgSnapshotTest(
+        `
+     sequenceDiagram
+      Alice--\\\\John: Hello John, how are you?
+      Alice--\\\\John: Hi Alice, I can hear you!
+      Alice--\\\\John: Test`
+      );
+    });
+
+    it('should render Stick half arrow bottom dotted', () => {
+      imgSnapshotTest(
+        `
+     sequenceDiagram
+      Alice--//John: Hello John, how are you?
+      Alice--//John: Hi Alice, I can hear you!
+      Alice--//John: Test`
+      );
+    });
+
+    it('should render Solid half arrow top reverse dotted', () => {
+      imgSnapshotTest(
+        `
+  sequenceDiagram
+      Alice/|--John: Hello Alice, how are you?
+      Alice/|--John: Hi Alice, I can hear you!
+      Alice/|--John: Test`
+      );
+    });
+
+    it('should render Solid half arrow bottom reverse dotted', () => {
+      imgSnapshotTest(
+        `
+  sequenceDiagram
+      Alice\\|--John: Hello Alice, how are you?
+      Alice\\|--John: Hi Alice, I can hear you!
+      Alice\\|--John: Test`
+      );
+    });
+
+    it('should render Stick half arrow top reverse dotted ', () => {
+      imgSnapshotTest(
+        `
+  sequenceDiagram
+      Alice//--John: Hello Alice, how are you?
+      Alice//--John: Hi Alice, I can hear you!
+      Alice//--John: Test`
+      );
+    });
+
+    it('should render Stick half arrow bottom reverse dotted ', () => {
+      imgSnapshotTest(
+        `
+  sequenceDiagram
+      Alice\\\\--John: Hello Alice, how are you?
+      Alice\\\\--John: Hi Alice, I can hear you!
+      Alice\\\\--John: Test`
+      );
+    });
+  });
 });

docs/syntax/sequenceDiagram.md

@@ -329,7 +329,11 @@ Messages can be of two displayed either solid or with a dotted line.
 [Actor][Arrow][Actor]:Message text
 ```
 
-There are ten types of arrows currently supported:
+Lines can be solid or dotted, and can end with various types of arrowheads, crosses, or open arrows.
+
+#### Supported Arrow Types
+
+**Standard Arrow Types**
 
 | Type     | Description                                          |
 | -------- | ---------------------------------------------------- |
@@ -344,6 +348,58 @@ There are ten types of arrows currently supported:
 | `-)`     | Solid line with an open arrow at the end (async)     |
 | `--)`    | Dotted line with a open arrow at the end (async)     |
 
+**Half-Arrows (v\<MERMAID_RELEASE_VERSION>+)**
+
+The following half-arrow types are supported for more expressive sequence diagrams. Both solid and dotted variants are available by increasing the number of dashes (`-` → `--`).
+
+---
+
+| Type    | Description                                          |
+| ------- | ---------------------------------------------------- |
+| `-\|\`  | Solid line with top half arrowhead                   |
+| `--\|\` | Dotted line with top half arrowhead                  |
+| `-\|/`  | Solid line with bottom half arrowhead                |
+| `--\|/` | Dotted line with bottom half arrowhead               |
+| `/\|-`  | Solid line with reverse top half arrowhead           |
+| `/\|--` | Dotted line with reverse top half arrowhead          |
+| `\\-`   | Solid line with reverse bottom half arrowhead        |
+| `\\--`  | Dotted line with reverse bottom half arrowhead       |
+| `-\\`   | Solid line with top stick half arrowhead             |
+| `--\\`  | Dotted line with top stick half arrowhead            |
+| `-//`   | Solid line with bottom stick half arrowhead          |
+| `--//`  | Dotted line with bottom stick half arrowhead         |
+| `//-`   | Solid line with reverse top stick half arrowhead     |
+| `//--`  | Dotted line with reverse top stick half arrowhead    |
+| `\\-`   | Solid line with reverse bottom stick half arrowhead  |
+| `\\--`  | Dotted line with reverse bottom stick half arrowhead |
+
+## Central Connections (v\<MERMAID_RELEASE_VERSION>+)
+
+Mermaid sequence diagrams support **central lifeline connections** using a `()`.
+This is useful to represent messages or signals that connect to a central point, rather than from one actor directly to another.
+
+To indicate a central connection, append `()` to the arrow syntax.
+
+#### Basic Syntax
+
+```mermaid-example
+sequenceDiagram
+    participant Alice
+    participant John
+    Alice->>()John: Hello John
+    Alice()->>John: How are you?
+    John()->>()Alice: Great!
+```
+
+```mermaid
+sequenceDiagram
+    participant Alice
+    participant John
+    Alice->>()John: Hello John
+    Alice()->>John: How are you?
+    John()->>()Alice: Great!
+```
+
 ## Activations
 
 It is possible to activate and deactivate an actor. (de)activation can be dedicated declarations: