diff --git a/ext/fg/js/driver.js b/ext/fg/js/driver.js
index 1c797201..c0f0afe9 100644
--- a/ext/fg/js/driver.js
+++ b/ext/fg/js/driver.js
@@ -32,11 +32,11 @@ class Driver {
         window.addEventListener('mousedown', this.onMouseDown.bind(this));
         window.addEventListener('mousemove', this.onMouseMove.bind(this));
         window.addEventListener('keydown', this.onKeyDown.bind(this));
-        window.addEventListener('resize', e => this.hidePopup());
+        window.addEventListener('resize', e => this.searchClear());
 
         getOptions().then(opts => {
             this.options = opts;
-            return getEnabled();
+            return isEnabled();
         }).then(enabled => {
             this.enabled = enabled;
         });
@@ -60,7 +60,7 @@ class Driver {
         if (this.enabled && this.lastMousePos !== null && e.keyCode === 16 /* shift */) {
             this.searchAt(this.lastMousePos, true);
         } else if (e.keyCode === 27 /* esc */) {
-            this.hidePopup();
+            this.searchClear();
         }
     }
 
@@ -87,7 +87,7 @@ class Driver {
         }
 
         const searcher = () => this.searchAt(this.lastMousePos, false);
-        if (!this.popup.visible() || e.shiftKey || e.which === 2 /* mmb */) {
+        if (!this.popup.isVisible() || e.shiftKey || e.which === 2 /* mmb */) {
             searcher();
         } else {
             this.popupTimerSet(searcher);
@@ -97,7 +97,7 @@ class Driver {
     onMouseDown(e) {
         this.lastMousePos = {x: e.clientX, y: e.clientY};
         this.popupTimerClear();
-        this.hidePopup();
+        this.searchClear();
     }
 
     onBgMessage({action, params}, sender, callback) {
@@ -117,14 +117,14 @@ class Driver {
         const textSource = textSourceFromPoint(point);
         if (textSource === null || !textSource.containsPoint(point)) {
             if (hideNotFound) {
-                this.hidePopup();
+                this.searchClear();
             }
 
             return;
         }
 
         if (this.lastTextSource !== null && this.lastTextSource.equals(textSource)) {
-            return true;
+            return;
         }
 
         this.pendingLookup = true;
@@ -132,12 +132,12 @@ class Driver {
             if (!found) {
                 this.searchKanji(textSource).then(found => {
                     if (!found && hideNotFound) {
-                        this.hidePopup();
+                        this.searchClear();
                     }
                 });
             }
         }).catch(error => {
-            alert('Error: ' + error);
+            window.alert('Error: ' + error);
         }).then(() => {
             this.pendingLookup = false;
         });
@@ -159,12 +159,13 @@ class Driver {
                 });
 
                 this.popup.showNextTo(textSource.getRect());
-                this.popup.invoke('showTermDefs', {definitions, options: this.options});
+                this.popup.showTermDefs(definitions, this.options);
 
                 return true;
             }
         }).catch(error => {
-            alert('Error: ' + error);
+            window.alert('Error: ' + error);
+            return false;
         });
     }
 
@@ -178,16 +179,17 @@ class Driver {
                 definitions.forEach(definition => definition.url = window.location.href);
 
                 this.popup.showNextTo(textSource.getRect());
-                this.popup.invoke('showKanjiDefs', {definitions, options: this.options});
+                this.popup.showKanjiDefs(definitions, this.options);
 
                 return true;
             }
         }).catch(error => {
-            alert('Error: ' + error);
+            window.alert('Error: ' + error);
+            return false;
         });
     }
 
-    hidePopup() {
+    searchClear() {
         this.popup.hide();
 
         if (this.options.selectMatchedText && this.lastTextSource !== null) {
@@ -195,7 +197,6 @@ class Driver {
         }
 
         this.lastTextSource = null;
-        this.definitions = null;
     }
 
     api_setOptions(opts) {
@@ -204,7 +205,7 @@ class Driver {
 
     api_setEnabled(enabled) {
         if (!(this.enabled = enabled)) {
-            this.hidePopup();
+            this.searchClear();
         }
     }
 }
diff --git a/ext/fg/js/frame.js b/ext/fg/js/frame.js
index 4a086abb..95762d5e 100644
--- a/ext/fg/js/frame.js
+++ b/ext/fg/js/frame.js
@@ -16,7 +16,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-class FrameContext {
+class Frame {
     constructor() {
         this.definitions = [];
         this.audioCache = {};
@@ -156,4 +156,4 @@ class FrameContext {
     }
 }
 
-window.frameContext = new FrameContext();
+window.frame = new Frame();
diff --git a/ext/fg/js/popup.js b/ext/fg/js/popup.js
index 35d7a00f..21f4a9d7 100644
--- a/ext/fg/js/popup.js
+++ b/ext/fg/js/popup.js
@@ -30,7 +30,7 @@ class Popup {
         document.body.appendChild(this.container);
     }
 
-    show(rect) {
+    showAt(rect) {
         this.container.style.left = rect.x + 'px';
         this.container.style.top = rect.y + 'px';
         this.container.style.height = rect.height + 'px';
@@ -59,22 +59,26 @@ class Popup {
             y = elementRect.top - height - this.offset;
         }
 
-        this.show({x, y, width, height});
-    }
-
-    visible() {
-        return this.container !== null && this.container.style.visibility !== 'hidden';
+        this.showAt({x, y, width, height});
     }
 
     hide() {
-        if (this.container !== null) {
-            this.container.style.visibility = 'hidden';
-        }
+        this.container.style.visibility = 'hidden';
     }
 
-    invoke(action, params) {
-        if (this.container !== null) {
-            this.container.contentWindow.postMessage({action, params}, '*');
-        }
+    isVisible() {
+        return this.container.style.visibility !== 'hidden';
+    }
+
+    showTermDefs(definitions, options) {
+        this.invokeApi('showTermDefs', {definitions, options});
+    }
+
+    showKanjiDefs(definitions, options) {
+        this.invokeApi('showKanjiDefs', {definitions, options});
+    }
+
+    invokeApi(action, params) {
+        this.container.contentWindow.postMessage({action, params}, '*');
     }
 }
diff --git a/ext/fg/js/util.js b/ext/fg/js/util.js
index 96007b74..aae044c5 100644
--- a/ext/fg/js/util.js
+++ b/ext/fg/js/util.js
@@ -17,7 +17,7 @@
  */
 
 
-function invokeApiBg(action, params) {
+function invokeBgApi(action, params) {
     return new Promise((resolve, reject) => {
         chrome.runtime.sendMessage({action, params}, ({result, error}) => {
             if (error) {
@@ -29,32 +29,32 @@ function invokeApiBg(action, params) {
     });
 }
 
-function getEnabled() {
-    return invokeApiBg('getEnabled', {});
+function isEnabled() {
+    return invokeBgApi('getEnabled', {});
 }
 
 function getOptions() {
-    return invokeApiBg('getOptions', {});
+    return invokeBgApi('getOptions', {});
 }
 
 function findTerm(text) {
-    return invokeApiBg('findTerm', {text});
+    return invokeBgApi('findTerm', {text});
 }
 
 function findKanji(text) {
-    return invokeApiBg('findKanji', {text});
+    return invokeBgApi('findKanji', {text});
 }
 
 function renderText(data, template) {
-    return invokeApiBg('renderText', {data, template});
+    return invokeBgApi('renderText', {data, template});
 }
 
 function canAddDefinitions(definitions, modes) {
-    return invokeApiBg('canAddDefinitions', {definitions, modes}).catch(() => null);
+    return invokeBgApi('canAddDefinitions', {definitions, modes}).catch(() => null);
 }
 
 function addDefinition(definition, mode) {
-    return invokeApiBg('addDefinition', {definition, mode});
+    return invokeBgApi('addDefinition', {definition, mode});
 }
 
 function textSourceFromPoint(point) {