#6856 Exposing elk configuration forceNodeModelOrder and considerModelOrder to the mermaid configuration

knsv · knsv · commit b9ef683fb67b · 2025-08-14T12:56:20.000+02:00
diff --git a/.changeset/busy-clocks-melt.md b/.changeset/busy-clocks-melt.md
@@ -0,0 +1,6 @@
+---
+'@mermaid-js/layout-elk': patch
+'mermaid': patch
+---
+
+feat: Exposing elk configuration forceNodeModelOrder and considerModelOrder to the mermaid configuration
diff --git a/cypress/platform/knsv2.html b/cypress/platform/knsv2.html
@@ -131,6 +131,22 @@
 
   <body>
     <pre id="diagram4" class="mermaid">
+---
+config:
+  layout: elk
+  elk:
+    mergeEdges: false
+    forceNodeModelOrder: false
+    considerModelOrder: NONE
+
+---
+            flowchart TB
+              a --> a1 & a2 & a3 & a4
+              b --> b1 & b2
+              b2 --> b3
+              b1 --> b4</pre
+    >
+    <pre id="diagram4" class="mermaid">
 treemap
 "Section 1"
     "Leaf 1.1": 12
diff --git a/docs/config/setup/defaultConfig/variables/configKeys.md b/docs/config/setup/defaultConfig/variables/configKeys.md
@@ -12,4 +12,4 @@
 
 > `const` **configKeys**: `Set`<`string`>
 
-Defined in: [packages/mermaid/src/defaultConfig.ts:290](https://github.com/mermaid-js/mermaid/blob/master/packages/mermaid/src/defaultConfig.ts#L290)
+Defined in: [packages/mermaid/src/defaultConfig.ts:292](https://github.com/mermaid-js/mermaid/blob/master/packages/mermaid/src/defaultConfig.ts#L292)
diff --git a/docs/config/setup/mermaid/interfaces/MermaidConfig.md b/docs/config/setup/mermaid/interfaces/MermaidConfig.md
diff --git a/packages/mermaid-layout-elk/src/render.ts b/packages/mermaid-layout-elk/src/render.ts
@@ -766,7 +766,10 @@ export const render = async (
     id: 'root',
     layoutOptions: {
       'elk.hierarchyHandling': 'INCLUDE_CHILDREN',
-      'elk.layered.considerModelOrder.strategy': 'NODES_AND_EDGES',
+      'elk.layered.crossingMinimization.forceNodeModelOrder':
+        data4Layout.config.elk?.forceNodeModelOrder,
+      'elk.layered.considerModelOrder.strategy': data4Layout.config.elk?.considerModelOrder,
+
       'elk.algorithm': algorithm,
       'nodePlacement.strategy': data4Layout.config.elk?.nodePlacementStrategy,
       'elk.layered.mergeEdges': data4Layout.config.elk?.mergeEdges,
diff --git a/packages/mermaid/src/config.type.ts b/packages/mermaid/src/config.type.ts
@@ -109,6 +109,16 @@ export interface MermaidConfig {
       | 'INTERACTIVE'
       | 'MODEL_ORDER'
       | 'GREEDY_MODEL_ORDER';
+    /**
+     * The node order given by the model does not change to produce a better layout. E.g. if node A is before node B in the model this is not changed during crossing minimization. This assumes that the node model order is already respected before crossing minimization. This can be achieved by setting considerModelOrder.strategy to NODES_AND_EDGES.
+     *
+     */
+    forceNodeModelOrder?: boolean;
+    /**
+     * Preserves the order of nodes and edges in the model file if this does not lead to additional edge crossings. Depending on the strategy this is not always possible since the node and edge order might be conflicting.
+     *
+     */
+    considerModelOrder?: 'NONE' | 'NODES_AND_EDGES' | 'PREFER_EDGES' | 'PREFER_NODES';
   };
   darkMode?: boolean;
   htmlLabels?: boolean;
diff --git a/packages/mermaid/src/defaultConfig.ts b/packages/mermaid/src/defaultConfig.ts
@@ -24,6 +24,8 @@ const config: RequiredDeep<MermaidConfig> = {
     // mergeEdges is needed here to be considered
     mergeEdges: false,
     nodePlacementStrategy: 'BRANDES_KOEPF',
+    forceNodeModelOrder: false,
+    considerModelOrder: 'NODES_AND_EDGES',
   },
   themeCSS: undefined,
 
diff --git a/packages/mermaid/src/schemas/config.schema.yaml b/packages/mermaid/src/schemas/config.schema.yaml
@@ -133,6 +133,21 @@ properties:
           - MODEL_ORDER
           - GREEDY_MODEL_ORDER
         default: GREEDY_MODEL_ORDER
+      forceNodeModelOrder:
+        description: |
+          The node order given by the model does not change to produce a better layout. E.g. if node A is before node B in the model this is not changed during crossing minimization. This assumes that the node model order is already respected before crossing minimization. This can be achieved by setting considerModelOrder.strategy to NODES_AND_EDGES.
+        type: boolean
+        default: false
+      considerModelOrder:
+        description: |
+          Preserves the order of nodes and edges in the model file if this does not lead to additional edge crossings. Depending on the strategy this is not always possible since the node and edge order might be conflicting.
+        type: string
+        enum:
+          - NONE
+          - NODES_AND_EDGES
+          - PREFER_EDGES
+          - PREFER_NODES
+        default: 'NODES_AND_EDGES'
   darkMode:
     type: boolean
     default: false
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml

Original file line number	Diff line number	Diff line change
`@@ -12,4 +12,4 @@`
`12`	`12`
`13`	`13`	> `const` configKeys: `Set`<`string`>
`14`	`14`
`15`		`-Defined in: [packages/mermaid/src/defaultConfig.ts:290](https://github.com/mermaid-js/mermaid/blob/master/packages/mermaid/src/defaultConfig.ts#L290)`
	`15`	`+Defined in: [packages/mermaid/src/defaultConfig.ts:292](https://github.com/mermaid-js/mermaid/blob/master/packages/mermaid/src/defaultConfig.ts#L292)`