maint(pat scroll box): Document that scroll-down and scroll-up classes are not cleared after scrolling has stopped.

Author: thet

src/pat/scroll-box/documentation.md

@@ -8,7 +8,9 @@ Ho(horizontal scrolling is not yet supported.
 
 The classes are:
 
--   `scroll-up`: when scrolling upwards,
--   `scroll-down`: when scrolling downwards,
+-   `scroll-up`: when scrolling upwards - the class is kept even after scrolling has stopped,
+-   `scroll-down`: when scrolling downwards - the class is kept even after scrolling has stopped,
+-   `scrolling-up`: when scrolling upwards - this class is removed after scrolling has stopped,
+-   `scrolling-down`: when scrolling downwards - this class is removed after scrolling has stopped,
 -   `scroll-position-top`: when the scrolling container is scrolled to the top,
 -   `scroll-position-bottom`: when the scrolling container is scrolled to the bottom.

src/pat/scroll-box/scroll-box.js

@@ -62,7 +62,6 @@ export default Base.extend({
         const to_add = [];
 
         if (scroll_pos < this.last_known_scroll_position) {
-            to_add.push("scroll-up");
             to_add.push("scroll-up");
             to_add.push("scrolling-up");
         } else if (this.last_known_scroll_position < scroll_pos) {
@@ -101,6 +100,8 @@ export default Base.extend({
     },
 
     clear_scrolling_classes() {
+        // Remove ``scrolling-up`` and ``scrolling-down``
+        // but keep ``scroll-up`` and ``scroll-down``.
         this.el.classList.remove("scrolling-up", "scrolling-down");
     },
 

src/pat/scroll-box/scroll-box.test.js

@@ -80,6 +80,8 @@ describe("pat-scroll-box", function () {
         expect(el.classList).not.toContain("scrolling-down");
 
         // Test for clearing the scrolling classes after a scroll stop
+        // scroll-up and scroll-down are not cleared.
+
         // Still there...
         await utils.timeout(custom_timeout / 2);
         expect(el.classList).toContain("scrolling-up");