Merge pull request #6683 from mermaid-js/6576-state-diagram-label-position

6576: State diagram edge label position

.changeset/cold-sites-accept.md

@@ -0,0 +1,5 @@
+---
+'mermaid': patch
+---
+
+fix: Position the edge label in state diagram correctly relative to the edge

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

@@ -602,6 +602,231 @@ State1 --> [*]
       --
       55
   }
+`,
+      {}
+    );
+  });
+  it('should render edge labels correctly', () => {
+    imgSnapshotTest(
+      `---
+title: On The Way To Something Something DarkSide
+config:
+  look: default
+  theme: default
+---
+
+stateDiagram-v2
+
+   state State1_____________
+   {
+      c0
+   }
+
+   state State2_____________
+   {
+      c1
+   }
+
+   state State3_____________
+   {
+      c7
+   }
+
+   state State4_____________
+   {
+      c2
+   }
+
+   state State5_____________
+   {
+      c3
+   }
+
+   state State6_____________
+   {
+      c4
+   }
+
+   state State7_____________
+   {
+      c5
+   }
+
+   state State8_____________
+   {
+      c6
+   }
+
+
+[*] --> State1_____________
+State1_____________ --> State2_____________   : Transition1_____
+State2_____________ --> State4_____________   : Transition2_____
+State2_____________ --> State3_____________   : Transition3_____
+State3_____________ --> State2_____________
+State4_____________ --> State2_____________   : Transition5_____
+State4_____________ --> State5_____________   : Transition6_____
+State5_____________ --> State6_____________   : Transition7_____
+State6_____________ --> State4_____________   : Transition8_____
+State2_____________ --> State7_____________   : Transition4_____
+State4_____________ --> State7_____________   : Transition4_____
+State5_____________ --> State7_____________   : Transition4_____
+State6_____________ --> State7_____________   : Transition4_____
+State7_____________ --> State1_____________   : Transition9_____
+State5_____________ --> State8_____________   : Transition10____
+State8_____________ --> State5_____________   : Transition11____
+`,
+      {}
+    );
+  });
+  it('should render edge labels correctly with multiple transitions', () => {
+    imgSnapshotTest(
+      `---
+title: Multiple Transitions
+config:
+  look: default
+  theme: default
+---
+
+stateDiagram-v2
+
+   state State1_____________
+   {
+      c0
+   }
+
+   state State2_____________
+   {
+      c1
+   }
+
+   state State3_____________
+   {
+      c7
+   }
+
+   state State4_____________
+   {
+      c2
+   }
+
+   state State5_____________
+   {
+      c3
+   }
+
+   state State6_____________
+   {
+      c4
+   }
+
+   state State7_____________
+   {
+      c5
+   }
+
+   state State8_____________
+   {
+      c6
+   }
+
+   state State9_____________
+   {
+      c9
+   }
+
+[*] --> State1_____________
+State1_____________ --> State2_____________   : Transition1_____
+State2_____________ --> State4_____________   : Transition2_____
+State2_____________ --> State3_____________   : Transition3_____
+State3_____________ --> State2_____________
+State4_____________ --> State2_____________   : Transition5_____
+State4_____________ --> State5_____________   : Transition6_____
+State5_____________ --> State6_____________   : Transition7_____
+State6_____________ --> State4_____________   : Transition8_____
+State2_____________ --> State7_____________   : Transition4_____
+State4_____________ --> State7_____________   : Transition4_____
+State5_____________ --> State7_____________   : Transition4_____
+State6_____________ --> State7_____________   : Transition4_____
+State7_____________ --> State1_____________   : Transition9_____
+State5_____________ --> State8_____________   : Transition10____
+State8_____________ --> State5_____________   : Transition11____
+State9_____________ --> State8_____________   : Transition12____
+`,
+      {}
+    );
+  });
+
+  it('should render edge labels correctly with multiple states', () => {
+    imgSnapshotTest(
+      `---
+title: Multiple States
+config:
+  look: default
+  theme: default
+---
+
+stateDiagram-v2
+
+   state State1_____________
+   {
+      c0
+   }
+
+   state State2_____________
+   {
+      c1
+   }
+
+   state State3_____________
+   {
+      c7
+   }
+
+   state State4_____________
+   {
+      c2
+   }
+
+   state State5_____________
+   {
+      c3
+   }
+
+   state State6_____________
+   {
+      c4
+   }
+
+   state State7_____________
+   {
+      c5
+   }
+
+   state State8_____________
+   {
+      c6
+   }
+
+   state State9_____________
+   {
+      c9
+   }
+
+   state State10_____________
+   {
+      c10
+   }
+
+[*] --> State1_____________
+State1_____________ --> State2_____________   : Transition1_____
+State2_____________ --> State3_____________   : Transition2_____
+State3_____________ --> State4_____________   : Transition3_____
+State4_____________ --> State5_____________   : Transition4_____
+State5_____________ --> State6_____________   : Transition5_____
+State6_____________ --> State7_____________   : Transition6_____
+State7_____________ --> State8_____________   : Transition7_____
+State8_____________ --> State9_____________   : Transition8_____
+State9_____________ --> State10_____________   : Transition9_____
 `,
       {}
     );

packages/mermaid/src/rendering-util/rendering-elements/edges.js

@@ -637,6 +637,11 @@ export const insertEdge = function (elem, edge, clusterDb, diagramType, startNod
   log.info('arrowTypeEnd', edge.arrowTypeEnd);
 
   addEdgeMarkers(svgPath, edge, url, id, diagramType, strokeColor);
+  const midIndex = Math.floor(points.length / 2);
+  const point = points[midIndex];
+  if (!utils.isLabelCoordinateInPath(point, svgPath.attr('d'))) {
+    pointsHasChanged = true;
+  }
 
   let paths = {};
   if (pointsHasChanged) {

packages/mermaid/src/utils.ts

@@ -884,6 +884,7 @@ export default {
   runFunc,
   entityDecode,
   insertTitle,
+  isLabelCoordinateInPath,
   parseFontSize,
   InitIDGenerator,
 };
@@ -960,3 +961,23 @@ export function handleUndefinedAttr(
 ) {
   return attrValue ?? null;
 }
+
+/**
+ * Checks if the  x or y coordinate of the edge label
+ * appears in the given SVG path data string.
+ *
+ * @param point  - The Point object with x and y properties to check.
+ * @param dAttr  - SVG path data string (the 'd' attribute of an SVG path element).
+ * @returns      - True if the rounded x or y coordinate of the edge label is found
+ *                 in the sanitized path data string; otherwise, false.
+ */
+export function isLabelCoordinateInPath(point: Point, dAttr: string) {
+  const roundedX = Math.round(point.x);
+  const roundedY = Math.round(point.y);
+
+  const sanitizedD = dAttr.replace(/(\d+\.\d+)/g, (match) =>
+    Math.round(parseFloat(match)).toString()
+  );
+
+  return sanitizedD.includes(roundedX.toString()) || sanitizedD.includes(roundedY.toString());
+}