fix os detector.

adjust some downloads styles.
edit a preference recommendation.

JS/osDetector.uc.js

@@ -1,6 +1,6 @@
 // ==UserScript==
 // @name           OS Detector
-// @version        1.2.0
+// @version        1.3.0
 // @author         aminomancer
 // @homepage       https://github.com/aminomancer/uc.css.js
 // @description    Set an attribute "operatingsystem" on the root element of the
@@ -16,6 +16,6 @@
 (function () {
   const AppConstants =
     window.AppConstants ??
-    ChromeUtils.import("resource://gre/modules/AppConstants.jsm")?.AppConstants;
-  document.documentElement.setAttribute("operatingsystem", AppConstants.platform);
+    window.ChromeUtils?.import("resource://gre/modules/AppConstants.jsm")?.AppConstants;
+  if (AppConstants) document.documentElement.setAttribute("operatingsystem", AppConstants.platform);
 })();

README.md

@@ -127,7 +127,7 @@ I also recommend setting the following prefs in `about:config`. There are two pr
 | <i>ui.systemUsesDarkTheme</i> | Number | 1 | Enable _browser_ dark scheme |
 | <i>layout.css.prefers-color-scheme.content-override</i> | Number | 0 | Enable _content_ dark scheme |
 | <i>ui.selecteditem</i> | String | `#2F3456` | Background for selected `<option>` elements and others |
-| <i>ui.highlight</i> | String | `hsla(245, 100%, 66%, .55)` | Selection background, among others |
+| <i>ui.highlight</i> | String | `hsl(250, 100%, 60%)` | Configure the system color "Highlight" |
 | <i>ui.selecteditemtext</i> | String | `#FFFFFFCC` | Text color for selected `<option>` elements and others |
 | ui.textHighlightBackground | String | `#7755FF` | These prefs control the appearance of text highlighted by the findbar. I choose white text on purple/pink background |
 | ui.textHighlightForeground | String | `#FFFFFF` | |

prefs/recommended.js

@@ -49,8 +49,8 @@ user_pref("browser.display.windows.non_native_menus", 1);
 user_pref("widget.content.allow-gtk-dark-theme", true);
 // keep "all tabs" menu available at all times, useful for all tabs menu expansion pack
 user_pref("browser.tabs.tabmanager.enabled", true);
-// Selection background, among others
-user_pref("ui.highlight", "hsla(245, 100%, 66%, .55)");
+// corresponds to the system color Highlight
+user_pref("ui.highlight", "hsl(250, 100%, 60%)");
 // Background for selected <option> elements and others
 user_pref("ui.selecteditem", "#2F3456");
 // Text color for selected <option> elements and others

resources/in-content/downloads.css

@@ -217,6 +217,8 @@
     background: var(--download-button-active-bg) !important;
   }
 
+  #downloadsListBox > richlistitem.download-state.downloadHoveringButton[state="1"][exists]:hover,
+  #downloadsListBox > richlistitem.download-state.downloadHoveringButton:is([verdict], .openWhenFinished):hover,
   richlistitem.download-state[state="1"][exists]:focus-within:not(:focus-visible),
   richlistitem.download-state:is([verdict], .openWhenFinished):focus-within:not(:focus-visible) {
     background: var(--download-button-focus-within-bg) !important;

resources/in-content/library.css

@@ -13,6 +13,9 @@
     --in-content-button-background-active: hsla(0, 20%, 90%, 0.19) !important;
     --in-content-button-background-bold: hsla(0, 20%, 90%, 0.23) !important;
     --in-content-border-hover: var(--dialog-box-border-hover) !important;
+    --arrowpanel-dimmed: color-mix(in srgb, currentColor 17%, transparent) !important;
+    --arrowpanel-dimmed-further: color-mix(in srgb, currentColor 25%, transparent) !important;
+    --arrowpanel-dimmed-even-further: color-mix(in srgb, currentColor 30%, transparent) !important;
     --organizer-color: var(--plaintext-color) !important;
     --organizer-deemphasized-color: color-mix(
       in srgb,