client: refactor

apps/client/src/widgets/containers/content-header.ts

@@ -0,0 +1,63 @@
+import { EventData } from "../../components/app_context";
+import BasicWidget from "../basic_widget";
+import Container from "./container";
+import NoteContext from "../../components/note_context";
+
+export default class ContentHeader extends Container<BasicWidget> {
+    
+    noteContext?: NoteContext;
+    thisElement?: HTMLElement;
+    parentElement?: HTMLElement;
+    resizeObserver: ResizeObserver;
+    currentHeight: number = 0;
+    currentSafeMargin: number = NaN;
+
+    constructor() {
+        super();
+
+        this.css("contain", "unset");
+        this.resizeObserver = new ResizeObserver(this.onResize.bind(this));
+    }
+
+    setNoteContextEvent({ noteContext }: EventData<"setNoteContext">) {
+        this.noteContext = noteContext;
+        this.init();
+    }
+
+    init() {
+        this.parentElement = this.parent!.$widget.get(0);
+
+        if (!this.parentElement) {
+            console.warn("No parent set for <ContentHeader>.");
+            return;
+        }
+
+        this.thisElement = this.$widget.get(0)!;
+
+        this.resizeObserver.observe(this.thisElement);
+        this.parentElement.addEventListener("scroll", this.updateSafeMargin.bind(this));
+    }
+
+    updateSafeMargin() {
+        const newSafeMargin = Math.max(this.currentHeight - this.parentElement!.scrollTop, 0);
+
+        if (newSafeMargin !== this.currentSafeMargin) {
+            this.currentSafeMargin = newSafeMargin;
+
+            this.triggerEvent("contentSafeMarginChanged", {
+                top: newSafeMargin,
+                noteContext: this.noteContext!
+            });
+        }
+    }
+
+    onResize(entries: ResizeObserverEntry[]) {
+        for (const entry of entries) {
+            if (entry.target === this.thisElement) {
+                this.currentHeight = entry.contentRect.height;
+                this.updateSafeMargin();
+            }
+        }
+    }
+
+}