Bug 1699841 - Hide the secondary text for locales where it doesn't fit, and always make the overlay icon visible in such locales. r=desktop-theme-reviewers,harry

Differential Revision: https://phabricator.services.mozilla.com/D109842

browser/app/profile/firefox.js

@@ -534,6 +534,10 @@ pref("browser.tabs.loadBookmarksInBackground", false);
 pref("browser.tabs.loadBookmarksInTabs", false);
 pref("browser.tabs.tabClipWidth", 140);
 pref("browser.tabs.tabMinWidth", 76);
+// Users running in any of the following language codes will have the
+// secondary text on tabs hidden due to size constraints and readability
+// of the text at small font sizes.
+pref("browser.tabs.secondaryTextUnsupportedLocales", "ar,bn,bo,ckb,fa,gu,he,hi,ja,km,kn,ko,lo,mr,my,ne,pa,si,ta,te,th,ur,zh");
 // Initial titlebar state is managed by -moz-gtk-csd-hide-titlebar-by-default
 // on Linux.
 #ifndef UNIX_BUT_NOT_MAC

browser/base/content/tabbrowser-tabs.js

@@ -70,6 +70,16 @@
       var tab = this.allTabs[0];
       tab.label = this.emptyTabTitle;
 
+      // Hide the secondary text for locales where it is unsupported due to size constraints.
+      const language = Services.locale.appLocaleAsBCP47;
+      const unsupportedLocales = Services.prefs.getCharPref(
+        "browser.tabs.secondaryTextUnsupportedLocales"
+      );
+      this.toggleAttribute(
+        "secondarytext-unsupported",
+        unsupportedLocales.split(",").includes(language.split("-")[0])
+      );
+
       this.newTabButton.setAttribute(
         "aria-label",
         GetDynamicShortcutTooltipText("tabs-newtab-button")

browser/themes/shared/tabs.inc.css

@@ -388,7 +388,8 @@
 } /*** END !proton ***/
 
 @supports -moz-bool-pref("browser.proton.tabs.enabled") {
-#toolbar-menubar:not(:hover) + #TabsToolbar:not(:hover) .tab-icon-overlay@tabIndicatorReplacesIcon@,
+#tabbrowser-tabs[secondarytext-unsupported] .tab-icon-stack@tabIndicatorReplacesIcon@ > :not(.tab-icon-overlay),
+#toolbar-menubar:not(:hover) + #TabsToolbar:not(:hover) #tabbrowser-tabs:not([secondarytext-unsupported]) .tab-icon-overlay@tabIndicatorReplacesIcon@,
 :is(#toolbar-menubar:hover + #TabsToolbar, #TabsToolbar:hover) .tab-icon-stack@tabIndicatorReplacesIcon@ > :not(.tab-icon-overlay) {
   opacity: 0;
 }
@@ -553,6 +554,7 @@
 } /*** END !proton ***/
 
 @supports -moz-bool-pref("browser.proton.tabs.enabled") {
+#tabbrowser-tabs[secondarytext-unsupported] .tab-secondary-label,
 .tab-label-container:not(.proton),
 .tab-label-container:not(.proton) + .tab-icon-sound {
   display: none;