Hello world

First open source release of Campfire 🎉

app/javascript/controllers/maintain_scroll_controller.js

@@ -0,0 +1,32 @@
+import { Controller } from "@hotwired/stimulus"
+import ScrollManager from "models/scroll_manager"
+
+export default class extends Controller {
+  #scrollManager
+
+  connect() {
+    this.#scrollManager = new ScrollManager(this.element)
+  }
+
+  // Actions
+
+  beforeStreamRender(event) {
+    const shouldKeepScroll = event.detail.newStream.hasAttribute("maintain_scroll")
+    const render = event.detail.render
+    const target = event.detail.newStream.getAttribute("target")
+    const targetElement = document.getElementById(target)
+
+    if (this.element.contains(targetElement) && shouldKeepScroll) {
+      const top = this.#isAboveFold(targetElement)
+      event.detail.render = async (streamElement) => {
+        this.#scrollManager.keepScroll(top, () => render(streamElement))
+      }
+    }
+  }
+
+  // Internal
+
+  #isAboveFold(element) {
+    return element.getBoundingClientRect().top < this.element.clientHeight
+  }
+}