feat: Overlap & distance based binding candidate selection

Signed-off-by: Mark Tolmacs <mark@lazycat.hu>

packages/element/src/collision.ts

@@ -291,54 +291,6 @@ const borderDistance = (
   return distance > tolerance ? -Infinity : -distance;
 };
 
-// const bindingBorderTest = (
-//   element: NonDeleted<ExcalidrawBindableElement>,
-//   [x, y]: Readonly<GlobalPoint>,
-//   elementsMap: NonDeletedSceneElementsMap,
-//   tolerance: number = 0,
-// ): boolean => {
-//   const p = pointFrom<GlobalPoint>(x, y);
-//   const shouldTestInside =
-//     // disable fullshape snapping for frame elements so we
-//     // can bind to frame children
-//     !isFrameLikeElement(element);
-
-//   // PERF: Run a cheap test to see if the binding element
-//   // is even close to the element
-//   const t = Math.max(1, tolerance);
-//   const bounds = [x - t, y - t, x + t, y + t] as Bounds;
-//   const elementBounds = getElementBounds(element, elementsMap);
-//   if (!doBoundsIntersect(bounds, elementBounds)) {
-//     return false;
-//   }
-
-//   // If the element is inside a frame, we should clip the element
-//   if (element.frameId) {
-//     const enclosingFrame = elementsMap.get(element.frameId);
-//     if (enclosingFrame && isFrameLikeElement(enclosingFrame)) {
-//       const enclosingFrameBounds = getElementBounds(
-//         enclosingFrame,
-//         elementsMap,
-//       );
-//       if (!pointInsideBounds(p, enclosingFrameBounds)) {
-//         return false;
-//       }
-//     }
-//   }
-
-//   // Do the intersection test against the element since it's close enough
-//   const intersections = intersectElementWithLineSegment(
-//     element,
-//     elementsMap,
-//     lineSegment(elementCenterPoint(element, elementsMap), p),
-//   );
-//   const distance = distanceToElement(element, elementsMap, p);
-
-//   return shouldTestInside
-//     ? intersections.length === 0 || distance <= tolerance
-//     : intersections.length > 0 && distance <= t;
-// };
-
 export const getAllHoveredElementAtPoint = (
   arrow: { elbowed: boolean },
   point: Readonly<GlobalPoint>,
@@ -347,7 +299,7 @@ export const getAllHoveredElementAtPoint = (
   tolerance?: number,
 ): NonDeleted<ExcalidrawBindableElement>[] => {
   const candidateElements: NonDeleted<ExcalidrawBindableElement>[] = [];
-  // We need to to hit testing from front (end of the array) to back (beginning of the array)
+  // We need to do hit testing from front (end of the array) to back (beginning of the array)
   // because array is ordered from lower z-index to highest and we want element z-index
   // with higher z-index
   for (let index = elements.length - 1; index >= 0; --index) {
@@ -400,7 +352,12 @@ export const getHoveredElementForBinding = (
       continue;
     }
 
-    const distance = borderDistance(element, point, elementsMap, tolerance);
+    const distance = borderDistance(
+      element,
+      point,
+      elementsMap,
+      tolerance ?? 0,
+    );
     const bindingGap = getBindingGap(element, arrow);
 
     if (distance > -(tolerance ?? bindingGap)) {
@@ -416,9 +373,44 @@ export const getHoveredElementForBinding = (
     return candidateElements[0].element;
   }
 
-  return candidateElements
-    .sort((a, b) => a.distance - b.distance)
-    .map((c) => c.element)[0];
+  const furthestDistance = candidateElements.sort(
+    (a, b) => a.distance - b.distance,
+  );
+
+  const candidate = furthestDistance[furthestDistance.length - 1].element;
+  const [cx1, cy1, cx2, cy2] = getElementBounds(candidate, elementsMap);
+  const candidateArea = Math.max(
+    0.00001,
+    Math.abs(cx2 - cx1) * Math.abs(cy2 - cy1),
+  );
+  const overlaps = furthestDistance
+    .map((c) => {
+      if (c.element === candidate) {
+        return { ...c, overlapPercent: 0, relativeArea: 1 };
+      }
+
+      const [x1, y1, x2, y2] = getElementBounds(c.element, elementsMap);
+      const overlapX1 = x1 > cx1 && x1 < cx2 ? x1 : cx1;
+      const overlapY1 = y1 > cy1 && y1 < cy2 ? y1 : cy1;
+      const overlapX2 = x2 < cx2 && x2 > cx1 ? x2 : cx2;
+      const overlapY2 = y2 < cy2 && y2 > cy1 ? y2 : cy2;
+      const overlapWdith =
+        overlapX1 !== cx1 || overlapX2 !== cx2 ? overlapX2 - overlapX1 : 0;
+      const overlapHeight =
+        overlapY1 !== cy1 || overlapY2 !== cy2 ? overlapY2 - overlapY1 : 0;
+      const area = Math.max(0.00001, Math.abs(x2 - x1) * Math.abs(y2 - y1));
+      const overlapPercent = Math.abs(overlapHeight * overlapWdith) / area;
+
+      return {
+        ...c,
+        overlapPercent,
+        relativeArea:
+          overlapPercent === 0 ? 1 : Math.min(area / candidateArea, 1),
+      };
+    })
+    .filter((c) => c.overlapPercent > 0.25 && c.relativeArea < 0.75);
+
+  return overlaps.length > 0 ? overlaps[0].element : candidate;
 };
 
 /**

packages/element/src/linearElementEditor.ts

@@ -344,7 +344,7 @@ export class LinearElementEditor {
 
     // Apply the point movement if needed
     let suggestedBinding: AppState["suggestedBinding"] = null;
-    const { positions, updates } = pointDraggingUpdates(
+    const { positions, updates, hit } = pointDraggingUpdates(
       [idx],
       deltaX,
       deltaY,
@@ -382,17 +382,20 @@ export class LinearElementEditor {
 
     // Move the arrow over the bindable object in terms of z-index
     if (isBindingElement(element)) {
-      moveArrowAboveBindable(
-        LinearElementEditor.getPointGlobalCoordinates(
+      if (hit) {
+        moveArrowAboveBindable(
+          LinearElementEditor.getPointGlobalCoordinates(
+            element,
+            element.points[element.points.length - 1],
+            elementsMap,
+          ),
           element,
-          element.points[element.points.length - 1],
+          elements,
           elementsMap,
-        ),
-        element,
-        elements,
-        elementsMap,
-        app.scene,
-      );
+          app.scene,
+          hit,
+        );
+      }
     }
 
     // PERF: Avoid state updates if not absolutely necessary
@@ -539,7 +542,7 @@ export class LinearElementEditor {
 
     // Apply the point movement if needed
     let suggestedBinding: AppState["suggestedBinding"] = null;
-    const { positions, updates } = pointDraggingUpdates(
+    const { positions, updates, hit } = pointDraggingUpdates(
       selectedPointsIndices,
       deltaX,
       deltaY,
@@ -578,19 +581,22 @@ export class LinearElementEditor {
 
     // Move the arrow over the bindable object in terms of z-index
     if (isBindingElement(element) && startIsSelected !== endIsSelected) {
-      moveArrowAboveBindable(
-        LinearElementEditor.getPointGlobalCoordinates(
+      if (hit) {
+        moveArrowAboveBindable(
+          LinearElementEditor.getPointGlobalCoordinates(
+            element,
+            startIsSelected
+              ? element.points[0]
+              : element.points[element.points.length - 1],
+            elementsMap,
+          ),
           element,
-          startIsSelected
-            ? element.points[0]
-            : element.points[element.points.length - 1],
+          elements,
           elementsMap,
-        ),
-        element,
-        elements,
-        elementsMap,
-        app.scene,
-      );
+          app.scene,
+          hit,
+        );
+      }
     }
 
     // Attached text might need to update if arrow dimensions change
@@ -2136,6 +2142,7 @@ const pointDraggingUpdates = (
 ): {
   positions: PointsPositionUpdates;
   updates?: PointMoveOtherUpdates;
+  hit?: ExcalidrawBindableElement | null;
 } => {
   const naiveDraggingPoints = new Map(
     selectedPointsIndices.map((pointIndex) => {
@@ -2497,6 +2504,7 @@ const pointDraggingUpdates = (
         ];
       }),
     ),
+    hit: startIsDragged ? start.element : end.element,
   };
 };
 

packages/element/src/zindex.ts

@@ -8,7 +8,6 @@ import { getElementsInGroup } from "./groups";
 import { syncMovedIndices } from "./fractionalIndex";
 import { getSelectedElements } from "./selection";
 import { getBoundTextElement, getContainerElement } from "./textElement";
-import { getHoveredElementForBinding } from "./collision";
 
 import type { Scene } from "./Scene";
 import type {
@@ -156,12 +155,8 @@ export const moveArrowAboveBindable = (
   elements: readonly Ordered<NonDeletedExcalidrawElement>[],
   elementsMap: NonDeletedSceneElementsMap,
   scene: Scene,
-  hit?: NonDeletedExcalidrawElement,
+  hoveredElement: NonDeletedExcalidrawElement,
 ): readonly OrderedExcalidrawElement[] => {
-  const hoveredElement = hit
-    ? hit
-    : getHoveredElementForBinding(arrow, point, elements, elementsMap);
-
   if (!hoveredElement) {
     return elements;
   }

packages/excalidraw/components/App.tsx

@@ -9887,17 +9887,16 @@ class App extends React.Component<AppProps, AppState> {
             return;
           }
 
-          if (isBindingElement(element)) {
+          if (isBindingElement(element) && getFeatureFlag("COMPLEX_BINDINGS")) {
             const hoveredElement = getHoveredElementForBinding(
               element,
               pointFrom<GlobalPoint>(pointerCoords.x, pointerCoords.y),
               this.scene.getNonDeletedElements(),
               elementsMap,
+              maxBindingDistance_simple(this.state.zoom),
             );
 
-            if (getFeatureFlag("COMPLEX_BINDINGS")) {
-              this.handleDelayedBindModeChange(element, hoveredElement);
-            }
+            this.handleDelayedBindModeChange(element, hoveredElement);
           }
 
           if (