WebUI: replace rounding function from MooTools

The `round()` returning floating point number is not a good idea. This is due to floating point
representation is imprecise and sometimes it cannot faithfully represent a number, for example
`0.09 + 0.01 !== 0.1 `. Therefore, it should be avoided and/or utilize other function
to achieve the goal.

Also, improve `window.qBittorrent.Misc.toFixedPointString()` and add test cases.

PR #22281.

src/webui/www/test/private/misc.test.js

@@ -0,0 +1,78 @@
+/*
+ * Bittorrent Client using Qt and libtorrent.
+ * Copyright (C) 2025  Mike Tzou (Chocobo1)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ *
+ * In addition, as a special exception, the copyright holders give permission to
+ * link this program with the OpenSSL project's "OpenSSL" library (or with
+ * modified versions of it that use the same license as the "OpenSSL" library),
+ * and distribute the linked executables. You must obey the GNU General Public
+ * License in all respects for all of the code used other than "OpenSSL".  If you
+ * modify file(s), you may extend this exception to your version of the file(s),
+ * but you are not obligated to do so. If you do not wish to do so, delete this
+ * exception statement from your version.
+ */
+
+import { expect, test } from "vitest";
+import "../../private/scripts/misc.js";
+
+test("Test toFixedPointString()", () => {
+    const toFixedPointString = window.qBittorrent.Misc.toFixedPointString;
+
+    expect(toFixedPointString(0, 0)).toBe("0");
+    expect(toFixedPointString(0, 1)).toBe("0.0");
+    expect(toFixedPointString(0, 2)).toBe("0.00");
+
+    expect(toFixedPointString(0.1, 0)).toBe("0");
+    expect(toFixedPointString(0.1, 1)).toBe("0.1");
+    expect(toFixedPointString(0.1, 2)).toBe("0.10");
+
+    expect(toFixedPointString(-0.1, 0)).toBe("0");
+    expect(toFixedPointString(-0.1, 1)).toBe("-0.1");
+    expect(toFixedPointString(-0.1, 2)).toBe("-0.10");
+
+    expect(toFixedPointString(1.005, 0)).toBe("1");
+    expect(toFixedPointString(1.005, 1)).toBe("1.0");
+    expect(toFixedPointString(1.005, 2)).toBe("1.00");
+    expect(toFixedPointString(1.005, 3)).toBe("1.005");
+    expect(toFixedPointString(1.005, 4)).toBe("1.0050");
+
+    expect(toFixedPointString(-1.005, 0)).toBe("-1");
+    expect(toFixedPointString(-1.005, 1)).toBe("-1.0");
+    expect(toFixedPointString(-1.005, 2)).toBe("-1.00");
+    expect(toFixedPointString(-1.005, 3)).toBe("-1.005");
+    expect(toFixedPointString(-1.005, 4)).toBe("-1.0050");
+
+    expect(toFixedPointString(35.855, 0)).toBe("35");
+    expect(toFixedPointString(35.855, 1)).toBe("35.8");
+    expect(toFixedPointString(35.855, 2)).toBe("35.85");
+    expect(toFixedPointString(35.855, 3)).toBe("35.855");
+    expect(toFixedPointString(35.855, 4)).toBe("35.8550");
+
+    expect(toFixedPointString(-35.855, 0)).toBe("-35");
+    expect(toFixedPointString(-35.855, 1)).toBe("-35.8");
+    expect(toFixedPointString(-35.855, 2)).toBe("-35.85");
+    expect(toFixedPointString(-35.855, 3)).toBe("-35.855");
+    expect(toFixedPointString(-35.855, 4)).toBe("-35.8550");
+
+    expect(toFixedPointString(100.00, 0)).toBe("100");
+    expect(toFixedPointString(100.00, 1)).toBe("100.0");
+    expect(toFixedPointString(100.00, 2)).toBe("100.00");
+
+    expect(toFixedPointString(-100.00, 0)).toBe("-100");
+    expect(toFixedPointString(-100.00, 1)).toBe("-100.0");
+    expect(toFixedPointString(-100.00, 2)).toBe("-100.00");
+});