snapshot of https://github.com/zulip/zulip.git @ 48c69911c7dd4e03b20552eb3bd77ad8151c1357 (2026-09-15)

web/tests/scroll_util.test.cjs

@@ -0,0 +1,123 @@
+"use strict";
+
+const assert = require("node:assert/strict");
+
+const {zrequire} = require("./lib/namespace.cjs");
+const {run_test} = require("./lib/test.cjs");
+
+const scroll_util = zrequire("scroll_util");
+
+run_test("scroll_delta", () => {
+    // If we are entirely on-screen, don't scroll
+    assert.equal(
+        0,
+        scroll_util.scroll_delta({
+            elem_top: 1,
+            elem_bottom: 9,
+            container_height: 10,
+        }),
+    );
+
+    assert.equal(
+        0,
+        scroll_util.scroll_delta({
+            elem_top: -5,
+            elem_bottom: 15,
+            container_height: 10,
+        }),
+    );
+
+    // The top is offscreen.
+    assert.equal(
+        -3,
+        scroll_util.scroll_delta({
+            elem_top: -3,
+            elem_bottom: 5,
+            container_height: 10,
+        }),
+    );
+
+    assert.equal(
+        -3,
+        scroll_util.scroll_delta({
+            elem_top: -3,
+            elem_bottom: -1,
+            container_height: 10,
+        }),
+    );
+
+    assert.equal(
+        -11,
+        scroll_util.scroll_delta({
+            elem_top: -150,
+            elem_bottom: -1,
+            container_height: 10,
+        }),
+    );
+
+    // The bottom is offscreen.
+    assert.equal(
+        3,
+        scroll_util.scroll_delta({
+            elem_top: 7,
+            elem_bottom: 13,
+            container_height: 10,
+        }),
+    );
+
+    assert.equal(
+        3,
+        scroll_util.scroll_delta({
+            elem_top: 11,
+            elem_bottom: 13,
+            container_height: 10,
+        }),
+    );
+
+    assert.equal(
+        11,
+        scroll_util.scroll_delta({
+            elem_top: 11,
+            elem_bottom: 99,
+            container_height: 10,
+        }),
+    );
+});
+
+run_test("scroll_element_into_container", () => {
+    const $container = (function () {
+        let top = 3;
+        return {
+            height: () => 100,
+            scrollTop: (arg) => {
+                if (arg === undefined) {
+                    return top;
+                }
+                top = arg;
+                return this;
+            },
+            offset: () => ({
+                top: 0,
+            }),
+            __zjquery: true,
+        };
+    })();
+
+    const $elem1 = {
+        innerHeight: () => 25,
+        offset: () => ({
+            top: 0,
+        }),
+    };
+    scroll_util.scroll_element_into_container($elem1, $container);
+    assert.equal($container.scrollTop(), 3);
+
+    const $elem2 = {
+        innerHeight: () => 15,
+        offset: () => ({
+            top: 250,
+        }),
+    };
+    scroll_util.scroll_element_into_container($elem2, $container);
+    assert.equal($container.scrollTop(), 250 - 100 + 3 + 15);
+});