support setting app font size

src/lib/settings.js

@@ -8,6 +8,7 @@ const serverSettingsCookieKey = 'ebk_server_settings';
 
 const defaultSettings = {
     theme: 'auto',
+    fontSize: 'default',
     timeZone: '',
     debug: false,
     applicationLock: false,
@@ -126,6 +127,8 @@ export default {
     isProduction: () => process.env.NODE_ENV === 'production',
     getTheme: () => getOption('theme'),
     setTheme: value => setOption('theme', value),
+    getFontSize: () => getOption('fontSize'),
+    setFontSize: value => setOption('fontSize', value),
     getTimezone: () => getOption('timeZone'),
     setTimezone: value => setOption('timeZone', value),
     isEnableDebug: () => getOption('debug'),

src/lib/ui.mobile.js

@@ -129,3 +129,19 @@ export function autoChangeTextareaSize(el) {
         el.style.height = el.scrollHeight + 'px';
     });
 }
+
+export function setAppFontSize(value) {
+    let fontSizeClass = 'font-default';
+
+    if (value === 'extraLarge') {
+        fontSizeClass = 'font-extra-large';
+    } else if (value === 'large') {
+        fontSizeClass = 'font-large';
+    }
+
+    elements('html')
+        .removeClass('font-default')
+        .removeClass('font-large')
+        .removeClass('font-extra-large')
+        .addClass(fontSizeClass);
+}