contrast text color on buttons

app/scripts/app.js

@@ -14,6 +14,12 @@ $(function() {
         return;
     }
     KeyHandler.init();
+
+    var appModel = new AppModel();
+    if (appModel.settings.get('theme')) {
+        document.body.setAttribute('class', 'th-' + appModel.settings.get('theme'));
+    }
+
     if (['https:', 'file:', 'app:'].indexOf(location.protocol) < 0) {
         Alerts.error({ header: 'Not Secure!', icon: 'user-secret', esc: false, enter: false, click: false,
             body: 'You have loaded this app with insecure connection. ' +
@@ -31,7 +37,6 @@ $(function() {
     }
 
     function showApp() {
-        var appModel = new AppModel();
         new AppView({ model: appModel }).render().showOpenFile(appModel.settings.get('lastOpenFile'));
     }
 });

app/styles/base/_buttons.scss

@@ -20,11 +20,12 @@
   @include th {
     border: 1px solid action-color();
     background-color: action-color();
-    color: text-color();
+    color: text-contrast-color(action-color());
 
     &.btn-error, &.btn-silent {
       border-color: base-border-color();
       background-color: transparent;
+      color: text-contrast-color(background-color());
     }
 
     &:hover {
@@ -38,7 +39,6 @@
         border-color: action-background-color-focus();
         background-color: rgba(action-background-color-focus(), .1);
       }
-      color: text-color();
     }
 
     &:active {

app/styles/base/_colors.scss

@@ -20,6 +20,7 @@ $violet: #d946db;
 @function muted-color-border() { @return mix(medium-color(), background-color(), 15%); }
 @function text-selection-bg-color() { @return rgba(action-color(), .3); }
 @function text-selection-bg-color-error() { @return rgba(error-color(), .8); }
+@function text-contrast-color($bg) { @if (lightness($bg) >= lightness(background-color())) { @return text-color(); } @else { @return background-color(); } }
 
 // Borders, shadows