Edited for FR guitar

static/js/song-controls.js

@@ -0,0 +1,35 @@
+const controls = document.querySelector(".controls");
+const song = document.querySelector("iframe.song").contentWindow;
+
+// Autoscroll
+var scroll;
+function pageScroll() {
+	song.scrollBy(0, 1);
+	scroll = setTimeout(pageScroll, 80);
+}
+
+document.querySelector("#autoscroll").addEventListener("click", function() {
+	if (this.classList.contains("active")) {
+		clearTimeout(scroll);
+	} else {
+		pageScroll();
+	}
+	this.classList.toggle("active");
+});
+
+// Scaling
+function pageScale(value) {
+	if (value === 0) {
+		song.document.body.style.transform = "scale(1)";
+		return;
+	}
+	const currentScale = parseFloat(song.document.body.style.transform.split("scale(")[1]) || 1;
+	song.document.body.style.transform = "scale(" + (currentScale + value) + ")";
+}
+
+controls.querySelector("#font-size-increase").addEventListener("click", () => pageScale(0.1));
+controls.querySelector("#font-size-decrease").addEventListener("click", () => pageScale(-0.1));
+controls.querySelector("#font-size-reset").addEventListener("click", () => pageScale(0));
+
+// Display the controls on JS-enabled browsers
+window.addEventListener("load", () => controls.classList.remove = "hidden");