show "x" to reset non-default values in usercss config individually

also:
* simplified CSS selectors where possible
* .config-name = var name, 1st element in <label>
* .config-value = var value, 2nd element in <label>
* .nondefault class added on <label>

manage/config-dialog.css

@@ -1,16 +1,15 @@
-#stylus-popup #message-box-contents {
+#stylus-manage .config-dialog #message-box-contents {
-  padding: .25rem .75rem;
+  padding: 2em 16px;
+}
+
+#stylus-popup .config-dialog #message-box-contents {
+  padding: 8px 16px;
 }
 
 #stylus-popup .config-body label {
   padding: .5em 0;
 }
 
-#stylus-popup .config-body label > :first-child {
-  max-width: 140px;
-  min-width: 140px;
-}
-
 .config-heading {
   float: right;
   margin: -1.25rem 0 0 0;
@@ -21,9 +20,10 @@
   display: flex;
   padding: .75em 0;
   align-items: center;
+  margin-right: -16px; /* for .config-reset-icon */
 }
 
-.config-dialog .select-resizer {
+.config-body .select-resizer {
   position: static;
 }
 
@@ -39,25 +39,16 @@
   border-top: 1px dotted #ccc;
 }
 
-.config-body label > :first-child {
+.config-body .dirty {
-  margin-right: 8px;
+  font-style: italic;
-  flex-grow: 1;
 }
 
-.config-body label:not([disabled]) > :first-child {
+.config-body .dirty:after {
-  cursor: default;
-}
-
-.config-dialog .dirty:after {
   content: "*";
   position: absolute;
   left: 6px;
 }
 
-.config-dialog .dirty {
-  font-style: italic;
-}
-
 .config-body input,
 .config-body select,
 .config-body .onoffswitch {
@@ -81,21 +72,48 @@
 .config-body .onoffswitch {
   height: auto;
   margin: calc((2em - 12px) / 2) 0;
+  flex-grow: 0;
 }
 
 .config-body input[type="text"] {
   padding-left: 0.25em;
 }
 
-.config-body label > :last-child {
+.config-name {
+  flex-grow: 1;
+  margin-right: 1em;
+}
+
+.config-value {
   box-sizing: border-box;
   flex-shrink: 0;
 }
 
-.config-body label > :last-child:not(.onoffswitch):not(.select-resizer) > :not(:last-child) {
+.config-value:not(.onoffswitch):not(.select-resizer) > :not(:last-child) {
   margin-right: 4px;
 }
 
+.config-body label:not(.nondefault) .config-reset-icon {
+  visibility: hidden;
+}
+
+.svg-icon.config-reset-icon {
+  /*position: absolute;*/
+  pointer-events: all !important;
+  cursor: pointer;
+  /*right: -7px;*/
+  fill: #aaa;
+  width: 16px;
+  height: 16px;
+  padding: 0 1px;
+  box-sizing: border-box;
+  flex-shrink: 0;
+}
+
+.svg-icon.config-reset-icon:hover {
+  fill: #666;
+}
+
 #config-autosave-wrapper {
   position: relative;
   padding: 0 0 0 16px;

manage/config-dialog.js

@@ -72,15 +72,17 @@ function configDialog(style) {
     colorpicker.hide();
   }
 
-  function onchange({target}) {
+  function onchange({target, justSaved = false}) {
     // invoked after element's own onchange so 'va' contains the updated value
     const va = target.va;
     if (va) {
       va.dirty = varsInitial[va.name] !== (isDefault(va) ? va.default : va.value);
-      if (prefs.get('config.autosave')) {
+      if (prefs.get('config.autosave') && !justSaved) {
         debounce(save, 0, {anyChangeIsDirty: true});
-      } else {
+        return;
-        target.closest('label').classList.toggle('dirty', va.dirty);
+      }
+      renderValueState(va);
+      if (!justSaved) {
         updateButtons();
       }
     }
@@ -148,7 +150,8 @@ function configDialog(style) {
     return BG.usercssHelper.save(style)
       .then(saved => {
         varsInitial = getInitialValues(deepCopy(saved.usercssData.vars));
-        vars.forEach(va => onchange({target: va.input}));
+        vars.forEach(va => onchange({target: va.input, justSaved: true}));
+        renderValues();
         updateButtons();
         $.remove('.config-error');
       })
@@ -172,12 +175,19 @@ function configDialog(style) {
   }
 
   function buildConfigForm() {
+    let resetter = $create('SVG:svg.svg-icon.config-reset-icon', {viewBox: '0 0 20 20'}, [
+      $create('SVG:title', t('genericResetLabel')),
+      $create('SVG:polygon', {
+        points: '16.2,5.5 14.5,3.8 10,8.3 5.5,3.8 3.8,5.5 8.3,10 3.8,14.5 ' +
+                '5.5,16.2 10,11.7 14.5,16.2 16.2,14.5 11.7,10',
+      }),
+    ]);
     for (const va of vars) {
       let children;
       switch (va.type) {
         case 'color':
           children = [
-            $create('.cm-colorview', [
+            $create('.cm-colorview.config-value', [
               va.input = $create('.color-swatch', {
                 va,
                 onclick: showColorpicker
@@ -188,7 +198,7 @@ function configDialog(style) {
 
         case 'checkbox':
           children = [
-            $create('span.onoffswitch', [
+            $create('span.onoffswitch.config-value', [
               va.input = $create('input.slider', {
                 va,
                 type: 'checkbox',
@@ -204,7 +214,7 @@ function configDialog(style) {
         case 'image':
           // TODO: a image picker input?
           children = [
-            $create('.select-resizer', [
+            $create('.select-resizer.config-value', [
               va.input = $create('select', {
                 va,
                 onchange: updateVarOnChange,
@@ -219,7 +229,7 @@ function configDialog(style) {
 
         default:
           children = [
-            va.input = $create('input', {
+            va.input = $create('input.config-value', {
               va,
               type: 'text',
               onchange: updateVarOnChange,
@@ -228,10 +238,16 @@ function configDialog(style) {
           ];
           break;
       }
+
+      resetter = resetter.cloneNode(true);
+      resetter.va = va;
+      resetter.onclick = resetOnClick;
+
       elements.push(
         $create(`label.config-${va.type}`, [
-          $create('span', va.label),
+          $create('span.config-name', tWordBreak(va.label)),
           ...children,
+          resetter,
         ]));
     }
   }
@@ -248,8 +264,8 @@ function configDialog(style) {
     }
   }
 
-  function renderValues() {
+  function renderValues(varsToRender = vars) {
-    for (const va of vars) {
+    for (const va of varsToRender) {
       const value = isDefault(va) ? va.default : va.value;
       if (va.type === 'color') {
         va.input.style.backgroundColor = value;
@@ -261,9 +277,25 @@ function configDialog(style) {
       } else {
         va.input.value = value;
       }
+      if (!prefs.get('config.autosave')) {
+        renderValueState(va);
+      }
     }
   }
 
+  function renderValueState(va) {
+    const el = va.input.closest('label');
+    el.classList.toggle('dirty', Boolean(va.dirty));
+    el.classList.toggle('nondefault', !isDefault(va));
+  }
+
+  function resetOnClick(event) {
+    event.preventDefault();
+    this.va.value = null;
+    renderValues([this.va]);
+    onchange({target: this.va.input});
+  }
+
   function showColorpicker() {
     window.removeEventListener('keydown', messageBox.listeners.key, true);
     const box = $('#message-box-contents');