Improve rendering of emoji which do not contrast with background (#13772)

* Refactor list of emoji requiring added outlines so that it can be theme-specific

* Split inaccessible emoji to emoji requiring an outline and ones that can be inverted

* Drop the “silouhettes” from black emoji as they seem to have changed color

* Add inaccessible emojis list for the light theme

* Use bordered emoji variant instead of unreliable CSS

2 files changed, 7 insertions, 6 deletions

diff --git a/app/javascript/styles/mastodon-light/variables.scss b/app/javascript/styles/mastodon-light/variables.scss
index c68944528..bc039ff03 100644
--- a/app/javascript/styles/mastodon-light/variables.scss
+++ b/app/javascript/styles/mastodon-light/variables.scss
@@ -39,3 +39,5 @@ $account-background-color: $white !default;
 @function lighten($color, $amount) {
   @return hsl(hue($color), saturation($color), lightness($color) - $amount);
 }
+
+$emojis-requiring-inversion: 'chains';
diff --git a/app/javascript/styles/mastodon/accessibility.scss b/app/javascript/styles/mastodon/accessibility.scss
index d33806c84..c5bcb5941 100644
--- a/app/javascript/styles/mastodon/accessibility.scss
+++ b/app/javascript/styles/mastodon/accessibility.scss
@@ -1,14 +1,13 @@
-$black-emojis: '8ball' 'ant' 'back' 'black_circle' 'black_heart' 'black_large_square' 'black_medium_small_square' 'black_medium_square' 'black_nib' 'black_small_square' 'bomb' 'bowling' 'bust_in_silhouette' 'busts_in_silhouette' 'camera' 'camera_with_flash' 'clubs' 'copyright' 'curly_loop' 'currency_exchange' 'dark_sunglasses' 'eight_pointed_black_star' 'electric_plug' 'end' 'female-guard' 'film_projector' 'fried_egg' 'gorilla' 'guardsman' 'heavy_check_mark' 'heavy_division_sign' 'heavy_dollar_sign' 'heavy_minus_sign' 'heavy_multiplication_x' 'heavy_plus_sign' 'hocho' 'hole' 'joystick' 'kaaba' 'lower_left_ballpoint_pen' 'lower_left_fountain_pen' 'male-guard' 'microphone' 'mortar_board' 'movie_camera' 'musical_score' 'on' 'registered' 'soon' 'spades' 'speaking_head_in_silhouette' 'spider' 'telephone_receiver' 'tm' 'top' 'tophat' 'turkey' 'vhs' 'video_camera' 'video_game' 'water_buffalo' 'waving_black_flag' 'wavy_dash';
+$emojis-requiring-inversion: 'back' 'copyright' 'curly_loop' 'currency_exchange' 'end' 'heavy_check_mark' 'heavy_division_sign' 'heavy_dollar_sign' 'heavy_minus_sign' 'heavy_multiplication_x' 'heavy_plus_sign' 'on' 'registered' 'soon' 'spider' 'telephone_receiver' 'tm' 'top' 'wavy_dash' !default;
 
-%white-emoji-outline {
-  filter: drop-shadow(1px 1px 0 $white) drop-shadow(-1px 1px 0 $white) drop-shadow(1px -1px 0 $white) drop-shadow(-1px -1px 0 $white);
-  transform: scale(.71);
+%emoji-color-inversion {
+  filter: invert(1);
 }
 
 .emojione {
-  @each $emoji in $black-emojis {
+  @each $emoji in $emojis-requiring-inversion {
     &[title=':#{$emoji}:'] {
-      @extend %white-emoji-outline;
+      @extend %emoji-color-inversion;
     }
   }
 }