fix(material/autocomplete): autocomplete panel top cut off in mobile landscape

Fixes Angular Components autocomplete so that when the panel is open in
mobile landscape that it does not cut off at the top and the panel
resizes/adjusts according to the viewport. Updates the previous fix to
avoid subscribing to handsetLandscapeSubscription as a side effect.

Fixes b/284148377

Author: essjay05

src/material/autocomplete/autocomplete-trigger.ts

@@ -139,7 +139,6 @@ export class MatAutocompleteTrigger
   private _scrollStrategy: () => ScrollStrategy;
   private _keydownSubscription: Subscription | null;
   private _outsideClickSubscription: Subscription | null;
-  private _handsetLandscapeBreakpointSubscription: Subscription | null;
 
   /** Old value of the native input. Used to work around issues with the `input` event on IE. */
   private _previousValue: string | number | null;
@@ -162,6 +161,10 @@ export class MatAutocompleteTrigger
   /** Subscription to viewport size changes. */
   private _viewportSubscription = Subscription.EMPTY;
 
+  /** Implements BreakpointObserver to be used to detect handset landscape */
+  private _breakpointObserver = inject(BreakpointObserver);
+  private _handsetLandscapeSubscription = Subscription.EMPTY;
+
   /**
    * Whether the autocomplete can open the next time it is focused. Used to prevent a focused,
    * closed autocomplete from being reopened if the user switches to another browser tab and then
@@ -283,7 +286,7 @@ export class MatAutocompleteTrigger
       window.removeEventListener('blur', this._windowBlurHandler);
     }
 
-    this._handsetLandscapeBreakpointSubscription?.unsubscribe();
+    this._handsetLandscapeSubscription.unsubscribe();
     this._viewportSubscription.unsubscribe();
     this._componentDestroyed = true;
     this._destroyPanel();
@@ -792,6 +795,23 @@ export class MatAutocompleteTrigger
           overlayRef.updateSize({width: this._getPanelWidth()});
         }
       });
+      // Subscribe to the breakpoint events stream to detect when screen is in
+      // handsetLandscape.
+      this._handsetLandscapeSubscription = this._breakpointObserver
+        .observe(Breakpoints.HandsetLandscape)
+        .subscribe(result => {
+          const isHandsetLandscape = result.matches;
+          // Check if result.matches Breakpoints.HandsetLandscape. Apply HandsetLandscape
+          // settings to prevent overlay cutoff in that breakpoint. Fixes b/284148377
+          if (isHandsetLandscape) {
+            this._positionStrategy
+              .withFlexibleDimensions(true)
+              .withGrowAfterOpen(true)
+              .withViewportMargin(8);
+          } else {
+            this._positionStrategy.withGrowAfterOpen(false);
+          }
+        });
     } else {
       // Update the trigger, panel width and direction, in case anything has changed.
       this._positionStrategy.setOrigin(this._getConnectedElement());
@@ -882,9 +902,6 @@ export class MatAutocompleteTrigger
     });
   }
 
-  /** Implements BreakpointObserver to be used to detect handset landscape */
-  private _breakpointObserver = inject(BreakpointObserver);
-
   private _getOverlayPosition(): PositionStrategy {
     // Set default Overlay Position
     const strategy = this._overlay
@@ -893,24 +910,6 @@ export class MatAutocompleteTrigger
       .withFlexibleDimensions(false)
       .withPush(false);
 
-    if (!this._handsetLandscapeBreakpointSubscription) {
-      // Subscribe to the breakpoint events stream to detect when screen is in
-      // handsetLandscape. Only subscribe if/when this panel is open.
-      // BreakpointObserver only returns screen size or isMatched/matches boolean.
-      this._handsetLandscapeBreakpointSubscription = this._breakpointObserver
-        .observe(Breakpoints.HandsetLandscape)
-        .subscribe(result => {
-          // Check breakpoint if being viewed in HandsetLandscape via subscription (if not null)
-          const isHandsetLandscape = result.matches;
-          // Apply HandsetLandscape settings to prevent overlay cutoff in that breakpoint
-          // Fixes b/284148377
-          if (isHandsetLandscape) {
-            strategy.withFlexibleDimensions(true).withGrowAfterOpen(true).withViewportMargin(8);
-          }
-          return;
-        });
-    }
-
     this._setStrategyPositions(strategy);
     this._positionStrategy = strategy;
     return strategy;