Set font option width

res/css/views/settings/tabs/user/_GeneralUserSettingsTab.scss

@@ -15,7 +15,8 @@ limitations under the License.
 */
 
 .mx_GeneralUserSettingsTab_changePassword .mx_Field,
-.mx_GeneralUserSettingsTab_themeSection .mx_Field {
+.mx_StyleUserSettingsTab_themeSection .mx_Field,
+.mx_StyleUserSettingsTab_fontScaling .mx_Field {
     @mixin mx_Settings_fullWidthField;
 }
 

res/css/views/settings/tabs/user/_StyleUserSettingsTab.scss

@@ -0,0 +1,20 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+.mx_StyleUserSettingsTab_themeSection .mx_Field,
+.mx_StyleUserSettingsTab_fontScaling .mx_Field {
+    @mixin mx_Settings_fullWidthField;
+}