feat(dropdown): add offsetDistance and offsetSkidding properties (#11614)

**Related Issue:** #7224 

## Summary

Adds offset properties for dropdown menu placement.

Author: jcfranco

packages/calcite-components/src/components/dropdown/dropdown.e2e.ts

@@ -39,6 +39,14 @@ describe("calcite-dropdown", () => {
 
   describe("defaults", () => {
     defaults("calcite-dropdown", [
+      {
+        propertyName: "offsetDistance",
+        defaultValue: 0,
+      },
+      {
+        propertyName: "offsetSkidding",
+        defaultValue: 0,
+      },
       {
         propertyName: "scale",
         defaultValue: "m",
@@ -52,6 +60,14 @@ describe("calcite-dropdown", () => {
 
   describe("reflects", () => {
     reflects("calcite-dropdown", [
+      {
+        propertyName: "offsetDistance",
+        value: 10,
+      },
+      {
+        propertyName: "offsetSkidding",
+        value: 10,
+      },
       {
         propertyName: "scale",
         value: "m",

packages/calcite-components/src/components/dropdown/dropdown.stories.ts

@@ -524,3 +524,19 @@ export const openInAllScales = (): string => html`
     </calcite-dropdown>
   </div>
 `;
+
+export const offsetPlacement = (): string => html`
+  <calcite-dropdown offset-skidding="10" offset-distance="10" open placement="leading">
+    <calcite-button icon-start="rectangle-plus" slot="trigger"></calcite-button>
+    <calcite-dropdown-group group-title="Add to new...">
+      <calcite-dropdown-item icon-start="nodes-link" selected>Link Chart</calcite-dropdown-item>
+      <calcite-dropdown-item icon-start="map">Map</calcite-dropdown-item>
+    </calcite-dropdown-group>
+    <calcite-dropdown-group group-title="Add to existing...">
+      <calcite-dropdown-item icon-start="nodes-link" selected>My Link Chart 1</calcite-dropdown-item>
+      <calcite-dropdown-item icon-start="nodes-link" selected>My Link Chart 2</calcite-dropdown-item>
+      <calcite-dropdown-item icon-start="map">My Map 1</calcite-dropdown-item>
+      <calcite-dropdown-item icon-start="map">My Map 2</calcite-dropdown-item>
+    </calcite-dropdown-group>
+  </calcite-dropdown>
+`;

packages/calcite-components/src/components/dropdown/dropdown.tsx

@@ -118,6 +118,16 @@ export class Dropdown
    */
   @property({ reflect: true }) maxItems = 0;
 
+  /**
+   * Offset the position of the component away from the `referenceElement`.
+   *
+   * @default 0
+   */
+  @property({ type: Number, reflect: true }) offsetDistance = 0;
+
+  /** Offset the position of the component along the `referenceElement`. */
+  @property({ reflect: true }) offsetSkidding = 0;
+
   /** When `true`, displays and positions the component. */
   @property({ reflect: true }) open = false;
 
@@ -171,13 +181,23 @@ export class Dropdown
    */
   @method()
   async reposition(delayed = false): Promise<void> {
-    const { floatingEl, referenceEl, placement, overlayPositioning, filteredFlipPlacements } = this;
+    const {
+      filteredFlipPlacements,
+      floatingEl,
+      offsetDistance,
+      offsetSkidding,
+      overlayPositioning,
+      placement,
+      referenceEl,
+    } = this;
 
     return reposition(
       this,
       {
         floatingEl,
         referenceEl,
+        offsetDistance,
+        offsetSkidding,
         overlayPositioning,
         placement,
         flipPlacements: filteredFlipPlacements,
@@ -257,9 +277,11 @@ export class Dropdown
     }
 
     if (
-      (changes.has("overlayPositioning") &&
-        (this.hasUpdated || this.overlayPositioning !== "absolute")) ||
-      (changes.has("placement") && (this.hasUpdated || this.placement !== defaultMenuPlacement))
+      this.hasUpdated &&
+      ((changes.has("offsetDistance") && this.offsetDistance !== 0) ||
+        (changes.has("offsetSkidding") && this.offsetSkidding !== 0) ||
+        (changes.has("overlayPositioning") && this.overlayPositioning !== "absolute") ||
+        (changes.has("placement") && this.placement !== defaultMenuPlacement))
     ) {
       this.reposition(true);
     }

packages/calcite-components/src/utils/floating-ui.ts

@@ -337,46 +337,40 @@ function getMiddleware({
   arrowEl?: SVGSVGElement;
   type: UIType;
 }): Middleware[] {
-  const defaultMiddleware = [shift(), hide()];
+  const middleware = [shift(), hide()];
 
   if (type === "menu") {
-    return [
-      ...defaultMiddleware,
+    middleware.push(
       flip({
         fallbackPlacements: flipPlacements || ["top-start", "top", "top-end", "bottom-start", "bottom", "bottom-end"],
       }),
-    ];
+    );
   }
 
-  if (type === "popover" || type === "tooltip") {
-    const middleware: Middleware[] = [
-      ...defaultMiddleware,
-      offset({
-        mainAxis: typeof offsetDistance === "number" ? offsetDistance : 0,
-        crossAxis: typeof offsetSkidding === "number" ? offsetSkidding : 0,
-      }),
-    ];
-
-    if (placement === "auto" || placement === "auto-start" || placement === "auto-end") {
-      middleware.push(
-        autoPlacement({ alignment: placement === "auto-start" ? "start" : placement === "auto-end" ? "end" : null }),
-      );
-    } else if (!flipDisabled) {
-      middleware.push(flip(flipPlacements ? { fallbackPlacements: flipPlacements } : {}));
-    }
+  middleware.push(
+    offset({
+      mainAxis: typeof offsetDistance === "number" ? offsetDistance : 0,
+      crossAxis: typeof offsetSkidding === "number" ? offsetSkidding : 0,
+    }),
+  );
 
-    if (arrowEl) {
-      middleware.push(
-        arrow({
-          element: arrowEl,
-        }),
-      );
-    }
+  if (placement === "auto" || placement === "auto-start" || placement === "auto-end") {
+    middleware.push(
+      autoPlacement({ alignment: placement === "auto-start" ? "start" : placement === "auto-end" ? "end" : null }),
+    );
+  } else if (!flipDisabled) {
+    middleware.push(flip(flipPlacements ? { fallbackPlacements: flipPlacements } : {}));
+  }
 
-    return middleware;
+  if (arrowEl) {
+    middleware.push(
+      arrow({
+        element: arrowEl,
+      }),
+    );
   }
 
-  return [];
+  return middleware;
 }
 
 export function filterValidFlipPlacements(placements: string[], el: HTMLElement): EffectivePlacement[] {