From 96d1dd28830d175a6e5dfc8264a7af5ae988b5c9 Mon Sep 17 00:00:00 2001
From: Michael Murtaugh <mm@automatist.org>
Date: Wed, 12 Jun 2019 11:12:06 +0200
Subject: [PATCH] custom scroller menu

---
 custom_scroller_menu.js | 101 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 custom_scroller_menu.js

diff --git a/custom_scroller_menu.js b/custom_scroller_menu.js
new file mode 100644
index 0000000..6dbd34e
--- /dev/null
+++ b/custom_scroller_menu.js
@@ -0,0 +1,101 @@
+function custom_scroller_menu (selt, menuelt, debug) {
+    function log () {
+        if (!debug) return;
+        console.log.apply(null, arguments);
+        var msg = "";
+        for (var i=0, l=arguments.length; i<l; i++) {
+            msg += arguments[i] + " ";
+        }
+        debug.innerHTML += "\n"+ msg;
+    }
+    // console.log("selt", selt);
+    // document.addEventListener("scroll", function (e) {
+    //     var sm = selt.scrollHeight - selt.clientHeight;
+    //     console.log("scroll", selt.scrollTop, sm, selt.scrollHeight);
+    // })
+    var dragging = false,
+        drag_ref_y = 0,
+        scroll_ref_y = 0,
+        last_y = 0,
+        starttime = null;
+
+    var hc = menuelt;
+
+    function touchstart (e) {
+        if (dragging) { return; }
+        var nn = e.target.nodeName.toLowerCase(),
+            touch = e;
+        if (e.touches) {
+            if (e.touches.length != 1) { return; }
+            touch = e.touches[0];
+        }
+        log("touchstart", nn);
+        if (nn == "img" || nn == "input") {
+            return;
+        }
+        if (nn !== "a") {
+            e.preventDefault();
+            e.stopPropagation();
+            drag_ref_y = touch.screenY;
+            last_y = touch.screenY;
+            scroll_ref_y = selt.scrollTop;
+            dragging = true;
+            starttime = new Date().getTime();
+            log("start drag", drag_ref_y, starttime);
+        } else {
+            log("headtouch", nn);
+        }        
+    }
+    function touchmove (e) {
+        if (dragging) {
+            var touch = e;
+            if (e.touches) {
+                touch = e.touches[0];
+            }
+            last_y = touch.screenY;
+            var dy = touch.screenY - drag_ref_y;
+            selt.scrollTop = scroll_ref_y - dy;
+        }
+    }
+    function touchend (e) {
+        if (dragging) {
+            log("touchend");
+            dragging = false;
+            var elapsed_time = new Date().getTime() - starttime;
+            // log("end of drag", elapsed_time);
+            if (elapsed_time <= 500) {
+                var open = false,
+                    scrollMax = selt.scrollHeight - selt.clientHeight;
+                // do a snap / throw ... direction ??
+                if (last_y == drag_ref_y) {
+                    // console.log("no change, guessing state");
+                    // toggle current state
+                    var sp = selt.scrollTop;
+                    log("guess", sp/scrollMax);
+                    open = ((sp / scrollMax) < 0.5);
+                } else {
+                    log("end/drag", last_y, drag_ref_y);
+                    open = (last_y < drag_ref_y);
+                }
+                log("THROW", open ? "open" : "closed");
+                if (open) {
+                    selt.scrollTop = scrollMax;
+                } else {
+                    selt.scrollTop = 0;
+                }
+            } else {
+                log("long", elapsed_time);
+            }            
+        }
+    }
+
+    menuelt.addEventListener("touchstart", touchstart);
+    menuelt.addEventListener("touchmove", touchmove);
+    menuelt.addEventListener("touchend", touchend);
+    menuelt.addEventListener("touchcancel", touchend);
+    menuelt.addEventListener("mousedown", touchstart);
+    menuelt.addEventListener("mousemove", touchmove);
+    menuelt.addEventListener("mouseup", touchend);
+    menuelt.addEventListener("mouseleave", touchend);
+
+}