Fix CJK fonts again and misc. font issues (#14575)

* Push system-ui further down the stack, fix #12966

* Fix Firefox showing U+300x in emoji font and more

* Revert emoji font and fix long-standing Safari bug

* Exclude Safari emoji fix above 1.25x zoom

* Minor correctness/typo fix, affects only legacy platforms

* Emoji consistency for monospace (e.g. EasyMDE)

* Override paradigm; macOS/iOS-specific metric fix

* Move whitespace fix to font-face

* Handle metric calculation errors with Firefox

* One last workaround for aliased fonts in Linux

2 files changed, 27 insertions, 1 deletions

diff --git a/web_src/js/index.js b/web_src/js/index.js
index 6c30d14fbb..64f4357329 100644
--- a/web_src/js/index.js
+++ b/web_src/js/index.js
@@ -26,7 +26,7 @@ import {initNotificationsTable, initNotificationCount} from './features/notifica
 import {initStopwatch} from './features/stopwatch.js';
 import {createCodeEditor, createMonaco} from './features/codeeditor.js';
 import {svg, svgs} from './svg.js';
-import {stripTags} from './utils.js';
+import {stripTags, mqBinarySearch} from './utils.js';
 
 const {AppSubUrl, StaticUrlPrefix, csrf} = window.config;
 
@@ -2519,6 +2519,19 @@ $(document).ready(async () => {
       .attr('title', '');
   });
 
+  // Undo Safari emoji glitch fix at high enough zoom levels
+  if (navigator.userAgent.match('Safari')) {
+    $(window).resize(() => {
+      const px = mqBinarySearch('width', 0, 4096, 1, 'px');
+      const em = mqBinarySearch('width', 0, 1024, 0.01, 'em');
+      if (em * 16 * 1.25 - px <= -1) {
+        $('body').addClass('safari-above125');
+      } else {
+        $('body').removeClass('safari-above125');
+      }
+    });
+  }
+
   // Semantic UI modules.
   $('.dropdown:not(.custom)').dropdown({
     fullTextSearch: 'exact'
diff --git a/web_src/js/utils.js b/web_src/js/utils.js
index fc65644c7b..bc84745066 100644
--- a/web_src/js/utils.js
+++ b/web_src/js/utils.js
@@ -28,3 +28,16 @@ export function uniq(arr) {
 export function stripTags(text) {
   return text.replace(/<[^>]*>?/gm, '');
 }
+
+// searches the inclusive range [minValue, maxValue].
+// credits: https://matthiasott.com/notes/write-your-media-queries-in-pixels-not-ems
+export function mqBinarySearch(feature, minValue, maxValue, step, unit) {
+  if (maxValue - minValue < step) {
+    return minValue;
+  }
+  const mid = Math.ceil((minValue + maxValue) / 2 / step) * step;
+  if (matchMedia(`screen and (min-${feature}:${mid}${unit})`).matches) {
+    return mqBinarySearch(feature, mid, maxValue, step, unit); // feature is >= mid
+  }
+  return mqBinarySearch(feature, minValue, mid - step, step, unit); // feature is < mid
+}