Shadow DOM container for popup iframes (#623)

* Add support for injecting stylesheets into a custom parent node

* Add api.getStylesheetContent

* Add support for injecting a CSS file's content

* Add usePopupShadowDom option

* Use a per-parentNode cache

* Add support for using a shadow DOM wrapper around popup iframes

* Ignore the popup container instead of the frame

2 files changed, 55 insertions, 9 deletions

diff --git a/ext/fg/js/frontend.js b/ext/fg/js/frontend.js
index ae0953f9..f6b0d236 100644
--- a/ext/fg/js/frontend.js
+++ b/ext/fg/js/frontend.js
@@ -345,7 +345,7 @@ class Frontend {
     }
 
     _ignoreElements() {
-        return this._popup === null || this._popup.isProxy() ? [] : [this._popup.getFrame()];
+        return this._popup === null || this._popup.isProxy() ? [] : [this._popup.getContainer()];
     }
 
     _ignorePoint(x, y) {
diff --git a/ext/fg/js/popup.js b/ext/fg/js/popup.js
index 3b14d3d0..5ee62c9b 100644
--- a/ext/fg/js/popup.js
+++ b/ext/fg/js/popup.js
@@ -47,6 +47,9 @@ class Popup {
         this._frame.style.width = '0';
         this._frame.style.height = '0';
 
+        this._container = this._frame;
+        this._shadow = null;
+
         this._fullscreenEventListeners = new EventListenerCollection();
     }
 
@@ -180,7 +183,12 @@ class Popup {
     }
 
     async setCustomOuterCss(css, useWebExtensionApi) {
-        return await dynamicLoader.loadStyle('yomichan-popup-outer-user-stylesheet', 'code', css, useWebExtensionApi);
+        let parentNode = null;
+        if (this._shadow !== null) {
+            useWebExtensionApi = false;
+            parentNode = this._shadow;
+        }
+        return await dynamicLoader.loadStyle('yomichan-popup-outer-user-stylesheet', 'code', css, useWebExtensionApi, parentNode);
     }
 
     setChildrenSupported(value) {
@@ -195,6 +203,10 @@ class Popup {
         return this._frame.getBoundingClientRect();
     }
 
+    getContainer() {
+        return this._container;
+    }
+
     // Private functions
 
     _inject() {
@@ -330,9 +342,9 @@ class Popup {
             throw new Error('Options not initialized');
         }
 
-        const {useSecurePopupFrameUrl} = this._options.general;
+        const {useSecurePopupFrameUrl, usePopupShadowDom} = this._options.general;
 
-        this._injectStyles();
+        await this._setUpContainer(usePopupShadowDom);
 
         const {secret, token} = await this._initializeFrame(this._frame, this._targetOrigin, this._frameId, (frame) => {
             frame.removeAttribute('src');
@@ -382,9 +394,9 @@ class Popup {
     }
 
     _resetFrame() {
-        const parent = this._frame.parentNode;
+        const parent = this._container.parentNode;
         if (parent !== null) {
-            parent.removeChild(this._frame);
+            parent.removeChild(this._container);
         }
         this._frame.removeAttribute('src');
         this._frame.removeAttribute('srcdoc');
@@ -395,9 +407,31 @@ class Popup {
         this._injectPromiseComplete = false;
     }
 
+    async _setUpContainer(usePopupShadowDom) {
+        if (usePopupShadowDom && typeof this._frame.attachShadow === 'function') {
+            const container = document.createElement('div');
+            container.style.setProperty('all', 'initial', 'important');
+            const shadow = container.attachShadow({mode: 'closed', delegatesFocus: true});
+            shadow.appendChild(this._frame);
+
+            this._container = container;
+            this._shadow = shadow;
+        } else {
+            const frameParentNode = this._frame.parentNode;
+            if (frameParentNode !== null) {
+                frameParentNode.removeChild(this._frame);
+            }
+
+            this._container = this._frame;
+            this._shadow = null;
+        }
+
+        await this._injectStyles();
+    }
+
     async _injectStyles() {
         try {
-            await dynamicLoader.loadStyle('yomichan-popup-outer-stylesheet', 'file', '/fg/css/client.css', true);
+            await this._injectPopupOuterStylesheet();
         } catch (e) {
             // NOP
         }
@@ -409,6 +443,18 @@ class Popup {
         }
     }
 
+    async _injectPopupOuterStylesheet() {
+        let fileType = 'file';
+        let useWebExtensionApi = true;
+        let parentNode = null;
+        if (this._shadow !== null) {
+            fileType = 'file-content';
+            useWebExtensionApi = false;
+            parentNode = this._shadow;
+        }
+        await dynamicLoader.loadStyle('yomichan-popup-outer-stylesheet', fileType, '/fg/css/client.css', useWebExtensionApi, parentNode);
+    }
+
     _observeFullscreen(observe) {
         if (!observe) {
             this._fullscreenEventListeners.removeAllEventListeners();
@@ -425,8 +471,8 @@ class Popup {
 
     _onFullscreenChanged() {
         const parent = this._getFrameParentElement();
-        if (parent !== null && this._frame.parentNode !== parent) {
-            parent.appendChild(this._frame);
+        if (parent !== null && this._container.parentNode !== parent) {
+            parent.appendChild(this._container);
         }
     }