fix: widen scale adjust workspace guard

app/api/canvas/local-edit/route.ts

@@ -425,6 +425,41 @@ function expandRectWithMargins(
   };
 }
 
+function getRectUnion(
+  leftRect: NormalizedLocalEditRegion["rect"],
+  rightRect: NormalizedLocalEditRegion["rect"]
+) {
+  const left = Math.min(leftRect.x, rightRect.x);
+  const top = Math.min(leftRect.y, rightRect.y);
+  const right = Math.max(
+    leftRect.x + leftRect.width,
+    rightRect.x + rightRect.width
+  );
+  const bottom = Math.max(
+    leftRect.y + leftRect.height,
+    rightRect.y + rightRect.height
+  );
+  return {
+    x: clamp(left, 0, 1),
+    y: clamp(top, 0, 1),
+    width: Math.max(0.001, clamp(right, 0, 1) - clamp(left, 0, 1)),
+    height: Math.max(0.001, clamp(bottom, 0, 1) - clamp(top, 0, 1)),
+  };
+}
+
+function rectsDifferMeaningfully(
+  leftRect: NormalizedLocalEditRegion["rect"],
+  rightRect: NormalizedLocalEditRegion["rect"],
+  epsilon = 0.0005
+) {
+  return (
+    Math.abs(leftRect.x - rightRect.x) > epsilon ||
+    Math.abs(leftRect.y - rightRect.y) > epsilon ||
+    Math.abs(leftRect.width - rightRect.width) > epsilon ||
+    Math.abs(leftRect.height - rightRect.height) > epsilon
+  );
+}
+
 function getScaleAdjustWorkspaceRect(
   sourceRect: NormalizedLocalEditRegion["rect"],
   targetRect: NormalizedLocalEditRegion["rect"],
@@ -432,37 +467,55 @@ function getScaleAdjustWorkspaceRect(
 ) {
   const sourceWidth = Math.max(0.0001, sourceRect.width);
   const sourceHeight = Math.max(0.0001, sourceRect.height);
-  const widthGrowthRatio = Math.max(0, targetRect.width / sourceWidth - 1);
-  const heightGrowthRatio = Math.max(0, targetRect.height / sourceHeight - 1);
-  const areaGrowthRatio = Math.max(
-    0,
+  const widthDeltaRatio = Math.abs(targetRect.width / sourceWidth - 1);
+  const heightDeltaRatio = Math.abs(targetRect.height / sourceHeight - 1);
+  const areaDeltaRatio = Math.abs(
     Math.sqrt(
       Math.max(0.0001, targetRect.width * targetRect.height) /
         Math.max(0.0001, sourceWidth * sourceHeight)
     ) - 1
   );
-  const explicitGrowthRatio = Math.max(
-    widthGrowthRatio,
-    heightGrowthRatio,
-    areaGrowthRatio
+  const sourceCenterX = sourceRect.x + sourceRect.width / 2;
+  const sourceCenterY = sourceRect.y + sourceRect.height / 2;
+  const targetCenterX = targetRect.x + targetRect.width / 2;
+  const targetCenterY = targetRect.y + targetRect.height / 2;
+  const movementRatioX = Math.abs(targetCenterX - sourceCenterX) / sourceWidth;
+  const movementRatioY = Math.abs(targetCenterY - sourceCenterY) / sourceHeight;
+  const explicitChangeRatio = Math.max(
+    widthDeltaRatio,
+    heightDeltaRatio,
+    areaDeltaRatio,
+    movementRatioX,
+    movementRatioY
   );
   const fallbackScaleRatio =
     typeof scalePercent === "number" && Number.isFinite(scalePercent)
-      ? Math.min(1, Math.max(0, scalePercent / 100))
+      ? Math.min(1, Math.abs(scalePercent) / 100)
       : 0;
-  const scaleRatio = Math.max(explicitGrowthRatio, fallbackScaleRatio);
-  if (scaleRatio <= 0) return targetRect;
+  const changeRatio = Math.max(explicitChangeRatio, fallbackScaleRatio);
+  const unionRect = getRectUnion(sourceRect, targetRect);
+  if (changeRatio <= 0 && !rectsDifferMeaningfully(unionRect, targetRect)) {
+    return targetRect;
+  }
 
   const marginX = Math.min(
-    0.12,
-    Math.max(0.018, sourceRect.width * scaleRatio * 0.22)
+    0.16,
+    Math.max(
+      0.018,
+      unionRect.width * 0.04,
+      sourceRect.width * changeRatio * 0.24
+    )
   );
   const marginY = Math.min(
-    0.12,
-    Math.max(0.018, sourceRect.height * scaleRatio * 0.22)
+    0.16,
+    Math.max(
+      0.018,
+      unionRect.height * 0.04,
+      sourceRect.height * changeRatio * 0.24
+    )
   );
 
-  return expandRectWithMargins(targetRect, marginX, marginY);
+  return expandRectWithMargins(unionRect, marginX, marginY);
 }
 
 function buildScaleAdjustCompositeRegions(
@@ -476,8 +529,8 @@ function buildScaleAdjustCompositeRegions(
       targetRect,
       scalePercent
     );
-    return workspaceRect.width > targetRect.width ||
-      workspaceRect.height > targetRect.height
+    return rectsDifferMeaningfully(workspaceRect, targetRect) &&
+      rectsDifferMeaningfully(workspaceRect, region.rect)
       ? [region.rect, targetRect, workspaceRect]
       : [region.rect, targetRect];
   });