Merge branch 'master' into testing

8 files changed, 390 insertions, 108 deletions

diff --git a/ext/fg/css/client.css b/ext/fg/css/client.css
index a9b8e025..a2b06d0f 100644
--- a/ext/fg/css/client.css
+++ b/ext/fg/css/client.css
@@ -26,6 +26,7 @@ iframe#yomichan-float {
     resize: both;
     visibility: hidden;
     z-index: 2147483647;
+    box-sizing: border-box;
 }
 
 iframe#yomichan-float.yomichan-float-full-width {
diff --git a/ext/fg/float.html b/ext/fg/float.html
index 07f2d58b..0133e653 100644
--- a/ext/fg/float.html
+++ b/ext/fg/float.html
@@ -34,6 +34,8 @@
         <script src="/mixed/lib/jquery.min.js"></script>
         <script src="/mixed/lib/wanakana.min.js"></script>
 
+        <script src="/mixed/js/extension.js"></script>
+
         <script src="/fg/js/api.js"></script>
         <script src="/fg/js/util.js"></script>
         <script src="/fg/js/document.js"></script>
diff --git a/ext/fg/js/document.js b/ext/fg/js/document.js
index 86396a8a..bd876e5d 100644
--- a/ext/fg/js/document.js
+++ b/ext/fg/js/document.js
@@ -17,77 +17,110 @@
  */
 
 
-const IS_FIREFOX = /Firefox/.test(navigator.userAgent);
+const REGEX_TRANSPARENT_COLOR = /rgba\s*\([^\)]*,\s*0(?:\.0+)?\s*\)/;
 
-function docOffsetCalc(element) {
-    const scrollTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop;
-    const scrollLeft = window.pageXOffset || document.documentElement.scrollLeft || document.body.scrollLeft;
-
-    const clientTop = document.documentElement.clientTop || document.body.clientTop || 0;
-    const clientLeft = document.documentElement.clientLeft || document.body.clientLeft || 0;
+function docSetImposterStyle(style, propertyName, value) {
+    style.setProperty(propertyName, value, 'important');
+}
 
-    const rect = element.getBoundingClientRect();
-    const top  = Math.round(rect.top +  scrollTop - clientTop);
-    const left = Math.round(rect.left + scrollLeft - clientLeft);
+function docImposterCreate(element, isTextarea) {
+    const elementStyle = window.getComputedStyle(element);
+    const elementRect = element.getBoundingClientRect();
+    const documentRect = document.documentElement.getBoundingClientRect();
+    const left = elementRect.left - documentRect.left;
+    const top = elementRect.top - documentRect.top;
+
+    // Container
+    const container = document.createElement('div');
+    const containerStyle = container.style;
+    docSetImposterStyle(containerStyle, 'all', 'initial');
+    docSetImposterStyle(containerStyle, 'position', 'absolute');
+    docSetImposterStyle(containerStyle, 'left', '0');
+    docSetImposterStyle(containerStyle, 'top', '0');
+    docSetImposterStyle(containerStyle, 'width', `${documentRect.width}px`);
+    docSetImposterStyle(containerStyle, 'height', `${documentRect.height}px`);
+    docSetImposterStyle(containerStyle, 'overflow', 'hidden');
+    docSetImposterStyle(containerStyle, 'opacity', '0');
+
+    docSetImposterStyle(containerStyle, 'pointer-events', 'none');
+    docSetImposterStyle(containerStyle, 'z-index', '2147483646');
+
+    // Imposter
+    const imposter = document.createElement('div');
+    const imposterStyle = imposter.style;
 
-    return {top, left};
-}
+    imposter.innerText = element.value;
 
-function docImposterCreate(element) {
-    const styleProps = window.getComputedStyle(element);
-    const stylePairs = [];
-    for (const key of styleProps) {
-        stylePairs.push(`${key}: ${styleProps[key]};`);
+    for (let i = 0, ii = elementStyle.length; i < ii; ++i) {
+        const property = elementStyle[i];
+        docSetImposterStyle(imposterStyle, property, elementStyle.getPropertyValue(property));
+    }
+    docSetImposterStyle(imposterStyle, 'position', 'absolute');
+    docSetImposterStyle(imposterStyle, 'top', `${top}px`);
+    docSetImposterStyle(imposterStyle, 'left', `${left}px`);
+    docSetImposterStyle(imposterStyle, 'margin', '0');
+    docSetImposterStyle(imposterStyle, 'pointer-events', 'auto');
+
+    if (isTextarea) {
+        if (elementStyle.overflow === 'visible') {
+            docSetImposterStyle(imposterStyle, 'overflow', 'auto');
+        }
+    } else {
+        docSetImposterStyle(imposterStyle, 'overflow', 'hidden');
+        docSetImposterStyle(imposterStyle, 'white-space', 'nowrap');
+        docSetImposterStyle(imposterStyle, 'line-height', elementStyle.height);
     }
 
-    const offset = docOffsetCalc(element);
-    const imposter = document.createElement('div');
-    imposter.className = 'yomichan-imposter';
-    imposter.innerText = element.value;
-    imposter.style.cssText = stylePairs.join('\n');
-    imposter.style.position = 'absolute';
-    imposter.style.top = `${offset.top}px`;
-    imposter.style.left = `${offset.left}px`;
-    imposter.style.opacity = 0;
-    imposter.style.zIndex = 2147483646;
-    if (element.nodeName === 'TEXTAREA' && styleProps.overflow === 'visible') {
-        imposter.style.overflow = 'auto';
+    container.appendChild(imposter);
+    document.body.appendChild(container);
+
+    // Adjust size
+    const imposterRect = imposter.getBoundingClientRect();
+    if (imposterRect.width !== elementRect.width || imposterRect.height !== elementRect.height) {
+        const width = parseFloat(elementStyle.width) + (elementRect.width - imposterRect.width);
+        const height = parseFloat(elementStyle.height) + (elementRect.height - imposterRect.height);
+        docSetImposterStyle(imposterStyle, 'width', `${width}px`);
+        docSetImposterStyle(imposterStyle, 'height', `${height}px`);
     }
 
-    document.body.appendChild(imposter);
     imposter.scrollTop = element.scrollTop;
     imposter.scrollLeft = element.scrollLeft;
 
-    return imposter;
-}
-
-function docImposterDestroy() {
-    for (const element of document.getElementsByClassName('yomichan-imposter')) {
-        element.parentNode.removeChild(element);
-    }
+    return [imposter, container];
 }
 
-function docRangeFromPoint(point) {
-    const element = document.elementFromPoint(point.x, point.y);
+function docRangeFromPoint({x, y}, options) {
+    const elements = document.elementsFromPoint(x, y);
     let imposter = null;
-    if (element) {
+    let imposterContainer = null;
+    if (elements.length > 0) {
+        const element = elements[0];
         switch (element.nodeName) {
             case 'IMG':
             case 'BUTTON':
                 return new TextSourceElement(element);
             case 'INPUT':
+                [imposter, imposterContainer] = docImposterCreate(element, false);
+                break;
             case 'TEXTAREA':
-                imposter = docImposterCreate(element);
+                [imposter, imposterContainer] = docImposterCreate(element, true);
                 break;
         }
     }
 
-    const range = document.caretRangeFromPoint(point.x, point.y);
-    if (imposter !== null) {
-        imposter.style.zIndex = -2147483646;
+    const range = caretRangeFromPointExt(x, y, options.scanning.deepDomScan ? elements : []);
+    if (range !== null) {
+        if (imposter !== null) {
+            docSetImposterStyle(imposterContainer.style, 'z-index', '-2147483646');
+            docSetImposterStyle(imposter.style, 'pointer-events', 'none');
+        }
+        return new TextSourceRange(range, '', imposterContainer);
+    } else {
+        if (imposterContainer !== null) {
+            imposterContainer.parentNode.removeChild(imposterContainer);
+        }
+        return null;
     }
-
-    return range !== null && isPointInRange(point, range) ? new TextSourceRange(range) : null;
 }
 
 function docSentenceExtract(source, extent) {
@@ -161,32 +194,158 @@ function docSentenceExtract(source, extent) {
     };
 }
 
-function isPointInRange(point, range) {
-    if (IS_FIREFOX) {
-        // Always return true on Firefox due to an issue where range.getClientRects()
-        // does not return a correct set of rects for characters at the beginning of a line.
-        return true;
+function isPointInRange(x, y, range) {
+    // Require a text node to start
+    if (range.startContainer.nodeType !== Node.TEXT_NODE) {
+        return false;
     }
 
-    const y = point.y - 2;
-    for (const rect of range.getClientRects()) {
-        if (y <= rect.bottom) {
+    // Scan forward
+    const nodePre = range.endContainer;
+    const offsetPre = range.endOffset;
+    try {
+        const {node, offset, content} = TextSourceRange.seekForward(range.endContainer, range.endOffset, 1);
+        range.setEnd(node, offset);
+
+        if (!isWhitespace(content) && isPointInAnyRect(x, y, range.getClientRects())) {
             return true;
         }
+    } finally {
+        range.setEnd(nodePre, offsetPre);
+    }
+
+    // Scan backward
+    const {node, offset, content} = TextSourceRange.seekBackward(range.startContainer, range.startOffset, 1);
+    range.setStart(node, offset);
+
+    if (!isWhitespace(content) && isPointInAnyRect(x, y, range.getClientRects())) {
+        // This purposefully leaves the starting offset as modified and sets the range length to 0.
+        range.setEnd(node, offset);
+        return true;
     }
 
+    // No match
+    return false;
+}
+
+function isWhitespace(string) {
+    return string.trim().length === 0;
+}
+
+function isPointInAnyRect(x, y, rects) {
+    for (const rect of rects) {
+        if (isPointInRect(x, y, rect)) {
+            return true;
+        }
+    }
     return false;
 }
 
-if (typeof document.caretRangeFromPoint !== 'function') {
-    document.caretRangeFromPoint = (x, y) => {
-        const position = document.caretPositionFromPoint(x, y);
-        if (position && position.offsetNode && position.offsetNode.nodeType === Node.TEXT_NODE) {
+function isPointInRect(x, y, rect) {
+    return (
+        x >= rect.left && x < rect.right &&
+        y >= rect.top && y < rect.bottom);
+}
+
+const caretRangeFromPoint = (() => {
+    if (typeof document.caretRangeFromPoint === 'function') {
+        // Chrome, Edge
+        return (x, y) => document.caretRangeFromPoint(x, y);
+    }
+
+    if (typeof document.caretPositionFromPoint === 'function') {
+        // Firefox
+        return (x, y) => {
+            const position = document.caretPositionFromPoint(x, y);
+            const node = position.offsetNode;
+            if (node === null) {
+                return null;
+            }
+
             const range = document.createRange();
-            range.setStart(position.offsetNode, position.offset);
-            range.setEnd(position.offsetNode, position.offset);
+            const offset = (node.nodeType === Node.TEXT_NODE ? position.offset : 0);
+            range.setStart(node, offset);
+            range.setEnd(node, offset);
             return range;
+        };
+    }
+
+    // No support
+    return () => null;
+})();
+
+function caretRangeFromPointExt(x, y, elements) {
+    const modifications = [];
+    try {
+        let i = 0;
+        let startContinerPre = null;
+        while (true) {
+            const range = caretRangeFromPoint(x, y);
+            if (range === null) {
+                return null;
+            }
+
+            const startContainer = range.startContainer;
+            if (startContinerPre !== startContainer) {
+                if (isPointInRange(x, y, range)) {
+                    return range;
+                }
+                startContinerPre = startContainer;
+            }
+
+            i = disableTransparentElement(elements, i, modifications);
+            if (i < 0) {
+                return null;
+            }
         }
-        return null;
-    };
+    } finally {
+        if (modifications.length > 0) {
+            restoreElementStyleModifications(modifications);
+        }
+    }
+}
+
+function disableTransparentElement(elements, i, modifications) {
+    while (true) {
+        if (i >= elements.length) {
+            return -1;
+        }
+
+        const element = elements[i++];
+        if (isElementTransparent(element)) {
+            const style = element.hasAttribute('style') ? element.getAttribute('style') : null;
+            modifications.push({element, style});
+            element.style.pointerEvents = 'none';
+            return i;
+        }
+    }
+}
+
+function restoreElementStyleModifications(modifications) {
+    for (const {element, style} of modifications) {
+        if (style === null) {
+            element.removeAttribute('style');
+        } else {
+            element.setAttribute('style', style);
+        }
+    }
+}
+
+function isElementTransparent(element) {
+    if (
+        element === document.body ||
+        element === document.documentElement
+    ) {
+        return false;
+    }
+    const style = window.getComputedStyle(element);
+    return (
+        parseFloat(style.opacity) < 0 ||
+        style.visibility === 'hidden' ||
+        (style.backgroundImage === 'none' && isColorTransparent(style.backgroundColor))
+    );
+}
+
+function isColorTransparent(cssColor) {
+    return REGEX_TRANSPARENT_COLOR.test(cssColor);
 }
diff --git a/ext/fg/js/float.js b/ext/fg/js/float.js
index 090839a1..c0ec8a15 100644
--- a/ext/fg/js/float.js
+++ b/ext/fg/js/float.js
@@ -23,7 +23,7 @@ class DisplayFloat extends Display {
         this.autoPlayAudioTimer = null;
         this.styleNode = null;
 
-        this.dependencies = {...this.dependencies, ...{docRangeFromPoint, docSentenceExtract}};
+        this.dependencies = Object.assign({}, this.dependencies, {docRangeFromPoint, docSentenceExtract});
 
         $(window).on('message', utilAsync(this.onMessage.bind(this)));
     }
diff --git a/ext/fg/js/frontend.js b/ext/fg/js/frontend.js
index 3c5f2ac8..8a5c48d0 100644
--- a/ext/fg/js/frontend.js
+++ b/ext/fg/js/frontend.js
@@ -285,7 +285,7 @@ class Frontend {
             return;
         }
 
-        const textSource = docRangeFromPoint(point);
+        const textSource = docRangeFromPoint(point, this.options);
         let hideResults = !textSource || !textSource.containsPoint(point);
         let searched = false;
         let success = false;
@@ -301,16 +301,21 @@ class Frontend {
         } catch (e) {
             if (window.yomichan_orphaned) {
                 if (textSource && this.options.scanning.modifier !== 'none') {
-                    this.popup.showOrphaned(textSource.getRect(), this.options);
+                    this.popup.showOrphaned(
+                        textSource.getRect(),
+                        textSource.getWritingMode(),
+                        this.options
+                    );
                 }
             } else {
                 this.onError(e);
             }
         } finally {
+            if (textSource !== null) {
+                textSource.cleanup();
+            }
             if (hideResults && this.options.scanning.autoHideResults) {
                 this.searchClear();
-            } else {
-                docImposterDestroy();
             }
 
             this.pendingLookup = false;
@@ -332,6 +337,7 @@ class Frontend {
         const url = window.location.href;
         this.popup.termsShow(
             textSource.getRect(),
+            textSource.getWritingMode(),
             definitions,
             this.options,
             {sentence, url, focus}
@@ -357,6 +363,7 @@ class Frontend {
         const url = window.location.href;
         this.popup.kanjiShow(
             textSource.getRect(),
+            textSource.getWritingMode(),
             definitions,
             this.options,
             {sentence, url, focus}
@@ -371,7 +378,6 @@ class Frontend {
     }
 
     searchClear() {
-        docImposterDestroy();
         this.popup.hide();
         this.popup.clearAutoPlayTimer();
 
diff --git a/ext/fg/js/popup.js b/ext/fg/js/popup.js
index 18dc0386..86ce575d 100644
--- a/ext/fg/js/popup.js
+++ b/ext/fg/js/popup.js
@@ -48,59 +48,132 @@ class Popup {
         return this.injected;
     }
 
-    async show(elementRect, options) {
+    async show(elementRect, writingMode, options) {
         await this.inject(options);
 
-        const containerStyle = window.getComputedStyle(this.container);
-        const containerHeight = parseInt(containerStyle.height);
-        const containerWidth = parseInt(containerStyle.width);
+        const optionsGeneral = options.general;
+        const container = this.container;
+        const containerRect = container.getBoundingClientRect();
+        const getPosition = (
+            writingMode === 'horizontal-tb' || optionsGeneral.popupVerticalTextPosition === 'default' ?
+            Popup.getPositionForHorizontalText :
+            Popup.getPositionForVerticalText
+        );
 
-        const limitX = document.body.clientWidth;
-        const limitY = window.innerHeight;
+        const [x, y, width, height, below] = getPosition(
+            elementRect,
+            Math.max(containerRect.width, optionsGeneral.popupWidth),
+            Math.max(containerRect.height, optionsGeneral.popupHeight),
+            document.body.clientWidth,
+            window.innerHeight,
+            optionsGeneral,
+            writingMode
+        );
 
-        let x = elementRect.left + options.general.popupHorizontalOffset;
-        let width = Math.max(containerWidth, options.general.popupWidth);
-        const overflowX = Math.max(x + width - limitX, 0);
+        container.classList.toggle('yomichan-float-full-width', optionsGeneral.popupDisplayMode === 'full-width');
+        container.classList.toggle('yomichan-float-above', !below);
+        container.style.left = `${x}px`;
+        container.style.top = `${y}px`;
+        container.style.width = `${width}px`;
+        container.style.height = `${height}px`;
+        container.style.visibility = 'visible';
+    }
+
+    static getPositionForHorizontalText(elementRect, width, height, maxWidth, maxHeight, optionsGeneral) {
+        let x = elementRect.left + optionsGeneral.popupHorizontalOffset;
+        const overflowX = Math.max(x + width - maxWidth, 0);
         if (overflowX > 0) {
             if (x >= overflowX) {
                 x -= overflowX;
             } else {
-                width = limitX;
+                width = maxWidth;
                 x = 0;
             }
         }
 
-        let above = false;
-        let y = 0;
-        let height = Math.max(containerHeight, options.general.popupHeight);
-        const yBelow = elementRect.bottom + options.general.popupVerticalOffset;
-        const yAbove = elementRect.top - options.general.popupVerticalOffset;
-        const overflowBelow = Math.max(yBelow + height - limitY, 0);
-        const overflowAbove = Math.max(height - yAbove, 0);
-        if (overflowBelow > 0 || overflowAbove > 0) {
-            if (overflowBelow < overflowAbove) {
-                height = Math.max(height - overflowBelow, 0);
-                y = yBelow;
+        const preferBelow = (optionsGeneral.popupHorizontalTextPosition === 'below');
+
+        const verticalOffset = optionsGeneral.popupVerticalOffset;
+        const [y, h, below] = Popup.limitGeometry(
+            elementRect.top - verticalOffset,
+            elementRect.bottom + verticalOffset,
+            height,
+            maxHeight,
+            preferBelow
+        );
+
+        return [x, y, width, h, below];
+    }
+
+    static getPositionForVerticalText(elementRect, width, height, maxWidth, maxHeight, optionsGeneral, writingMode) {
+        const preferRight = Popup.isVerticalTextPopupOnRight(optionsGeneral.popupVerticalTextPosition, writingMode);
+        const horizontalOffset = optionsGeneral.popupHorizontalOffset2;
+        const verticalOffset = optionsGeneral.popupVerticalOffset2;
+
+        const [x, w] = Popup.limitGeometry(
+            elementRect.left - horizontalOffset,
+            elementRect.right + horizontalOffset,
+            width,
+            maxWidth,
+            preferRight
+        );
+        const [y, h, below] = Popup.limitGeometry(
+            elementRect.bottom - verticalOffset,
+            elementRect.top + verticalOffset,
+            height,
+            maxHeight,
+            true
+        );
+        return [x, y, w, h, below];
+    }
+
+    static isVerticalTextPopupOnRight(positionPreference, writingMode) {
+        switch (positionPreference) {
+            case 'before':
+                return !Popup.isWritingModeLeftToRight(writingMode);
+            case 'after':
+                return Popup.isWritingModeLeftToRight(writingMode);
+            case 'left':
+                return false;
+            case 'right':
+                return true;
+        }
+    }
+
+    static isWritingModeLeftToRight(writingMode) {
+        switch (writingMode) {
+            case 'vertical-lr':
+            case 'sideways-lr':
+                return true;
+            default:
+                return false;
+        }
+    }
+
+    static limitGeometry(positionBefore, positionAfter, size, limit, preferAfter) {
+        let after = preferAfter;
+        let position = 0;
+        const overflowBefore = Math.max(0, size - positionBefore);
+        const overflowAfter = Math.max(0, positionAfter + size - limit);
+        if (overflowAfter > 0 || overflowBefore > 0) {
+            if (overflowAfter < overflowBefore) {
+                size = Math.max(0, size - overflowAfter);
+                position = positionAfter;
+                after = true;
             } else {
-                height = Math.max(height - overflowAbove, 0);
-                y = Math.max(yAbove - height, 0);
-                above = true;
+                size = Math.max(0, size - overflowBefore);
+                position = Math.max(0, positionBefore - size);
+                after = false;
             }
         } else {
-            y = yBelow;
+            position = preferAfter ? positionAfter : positionBefore - size;
         }
 
-        this.container.classList.toggle('yomichan-float-full-width', options.general.popupDisplayMode === 'full-width');
-        this.container.classList.toggle('yomichan-float-above', above);
-        this.container.style.left = `${x}px`;
-        this.container.style.top = `${y}px`;
-        this.container.style.width = `${width}px`;
-        this.container.style.height = `${height}px`;
-        this.container.style.visibility = 'visible';
+        return [position, size, after];
     }
 
-    async showOrphaned(elementRect, options) {
-        await this.show(elementRect, options);
+    async showOrphaned(elementRect, writingMode, options) {
+        await this.show(elementRect, writingMode, options);
         this.invokeApi('orphaned');
     }
 
@@ -136,13 +209,13 @@ class Popup {
         return contained;
     }
 
-    async termsShow(elementRect, definitions, options, context) {
-        await this.show(elementRect, options);
+    async termsShow(elementRect, writingMode, definitions, options, context) {
+        await this.show(elementRect, writingMode, options);
         this.invokeApi('termsShow', {definitions, options, context});
     }
 
-    async kanjiShow(elementRect, definitions, options, context) {
-        await this.show(elementRect, options);
+    async kanjiShow(elementRect, writingMode, definitions, options, context) {
+        await this.show(elementRect, writingMode, options);
         this.invokeApi('kanjiShow', {definitions, options, context});
     }
 
diff --git a/ext/fg/js/source.js b/ext/fg/js/source.js
index a360b331..e724488d 100644
--- a/ext/fg/js/source.js
+++ b/ext/fg/js/source.js
@@ -25,13 +25,20 @@ const IGNORE_TEXT_PATTERN = /\u200c/;
  */
 
 class TextSourceRange {
-    constructor(range, content='') {
+    constructor(range, content, imposterContainer) {
         this.range = range;
         this.content = content;
+        this.imposterContainer = imposterContainer;
     }
 
     clone() {
-        return new TextSourceRange(this.range.cloneRange(), this.content);
+        return new TextSourceRange(this.range.cloneRange(), this.content, this.imposterContainer);
+    }
+
+    cleanup() {
+        if (this.imposterContainer !== null && this.imposterContainer.parentNode !== null) {
+            this.imposterContainer.parentNode.removeChild(this.imposterContainer);
+        }
     }
 
     text() {
@@ -61,6 +68,10 @@ class TextSourceRange {
         return this.range.getBoundingClientRect();
     }
 
+    getWritingMode() {
+        return TextSourceRange.getElementWritingMode(TextSourceRange.getParentElement(this.range.startContainer));
+    }
+
     getPaddedRect() {
         const range = this.range.cloneRange();
         const startOffset = range.startOffset;
@@ -204,6 +215,23 @@ class TextSourceRange {
 
         return state.remainder > 0;
     }
+
+    static getParentElement(node) {
+        while (node !== null && node.nodeType !== Node.ELEMENT_NODE) {
+            node = node.parentNode;
+        }
+        return node;
+    }
+
+    static getElementWritingMode(element) {
+        if (element === null) {
+            return 'horizontal-tb';
+        }
+
+        const style = window.getComputedStyle(element);
+        const writingMode = style.writingMode;
+        return typeof writingMode === 'string' ? writingMode : 'horizontal-tb';
+    }
 }
 
 
@@ -221,6 +249,10 @@ class TextSourceElement {
         return new TextSourceElement(this.element, this.content);
     }
 
+    cleanup() {
+        // NOP
+    }
+
     text() {
         return this.content;
     }
@@ -267,6 +299,10 @@ class TextSourceElement {
         return this.element.getBoundingClientRect();
     }
 
+    getWritingMode() {
+        return 'horizontal-tb';
+    }
+
     select() {
         // NOP
     }
diff --git a/ext/fg/js/util.js b/ext/fg/js/util.js
index 954b3988..7518beb5 100644
--- a/ext/fg/js/util.js
+++ b/ext/fg/js/util.js
@@ -27,6 +27,7 @@ function utilInvoke(action, params={}) {
     return new Promise((resolve, reject) => {
         try {
             chrome.runtime.sendMessage({action, params}, (response) => {
+                utilCheckLastError(chrome.runtime.lastError);
                 if (response !== null && typeof response === 'object') {
                     if (response.error) {
                         reject(response.error);
@@ -43,3 +44,7 @@ function utilInvoke(action, params={}) {
         }
     });
 }
+
+function utilCheckLastError(e) {
+    // NOP
+}