Make startOpening/Closing abstract

packages/nimble-components/src/dialog/index.ts

@@ -56,6 +56,14 @@ export class Dialog<CloseReason = void> extends Modal<CloseReason> {
     ): void {
         this.footerIsEmpty = !next?.length;
     }
+
+    protected override startOpening(): void {
+        this.finishOpening();
+    }
+
+    protected override startClosing(reason: CloseReason | UserDismissed): void {
+        this.finishClosing(reason);
+    }
 }
 
 // eslint-disable-next-line @typescript-eslint/no-empty-interface

packages/nimble-components/src/drawer/index.ts

@@ -46,7 +46,7 @@ export class Drawer<CloseReason = void> extends Modal<CloseReason> {
     }
 
     protected override startOpening(): void {
-        super.startOpening();
+        this.finishOpening(); // has to be open before we can animate it
         this.triggerAnimation();
     }
 

packages/nimble-components/src/modal/index.ts

@@ -108,23 +108,15 @@ export abstract class Modal<CloseReason = void> extends FoundationElement {
         }
     }
 
-    // Derived classes can override this, but should not call it directly (except from the override).
-    protected startOpening(): void {
-        this.finishOpening();
-    }
+    protected abstract startOpening(): void;
 
-    // Overrides must call the base implementation, so that state gets updated.
     protected finishOpening(): void {
         this.state = ModalState.open;
         this.dialogElement.showModal();
     }
 
-    // Derived classes can override this, but should not call it directly (except from the override).
-    protected startClosing(reason: CloseReason | UserDismissed): void {
-        this.finishClosing(reason);
-    }
+    protected abstract startClosing(reason: CloseReason | UserDismissed): void;
 
-    // Overrides must call the base implementation, so that state gets updated.
     protected finishClosing(reason: CloseReason | UserDismissed): void {
         this.state = ModalState.closed;
         this.dialogElement.close();