1 files changed, 102 insertions, 0 deletions
diff --git a/ext/fg/js/frame-offset-forwarder.js b/ext/fg/js/frame-offset-forwarder.js
new file mode 100644
index 00000000..7b417b6e
--- /dev/null
+++ b/ext/fg/js/frame-offset-forwarder.js
@@ -0,0 +1,102 @@
+/*
+ * Copyright (C) 2020  Alex Yatskov <alex@foosoft.net>
+ * Author: Alex Yatskov <alex@foosoft.net>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/* global
+ * apiForward
+ */
+
+class FrameOffsetForwarder {
+    constructor() {
+        this._started = false;
+
+        this._forwardFrameOffset = (
+            window !== window.parent ?
+            this._forwardFrameOffsetParent.bind(this) :
+            this._forwardFrameOffsetOrigin.bind(this)
+        );
+
+        this._windowMessageHandlers = new Map([
+            ['getFrameOffset', ({offset, uniqueId}, e) => this._onGetFrameOffset(offset, uniqueId, e)]
+        ]);
+    }
+
+    start() {
+        if (this._started) { return; }
+        window.addEventListener('message', this.onMessage.bind(this), false);
+        this._started = true;
+    }
+
+    async getOffset() {
+        const uniqueId = yomichan.generateId(16);
+
+        const frameOffsetPromise = yomichan.getTemporaryListenerResult(
+            chrome.runtime.onMessage,
+            ({action, params}, {resolve}) => {
+                if (action === 'frameOffset' && isObject(params) && params.uniqueId === uniqueId) {
+                    resolve(params);
+                }
+            },
+            5000
+        );
+
+        window.parent.postMessage({
+            action: 'getFrameOffset',
+            params: {
+                uniqueId,
+                offset: [0, 0]
+            }
+        }, '*');
+
+        const {offset} = await frameOffsetPromise;
+        return offset;
+    }
+
+    onMessage(e) {
+        const {action, params} = e.data;
+        const handler = this._windowMessageHandlers.get(action);
+        if (typeof handler !== 'function') { return; }
+        handler(params, e);
+    }
+
+    _onGetFrameOffset(offset, uniqueId, e) {
+        let sourceFrame = null;
+        for (const frame of document.querySelectorAll('frame, iframe:not(.yomichan-float)')) {
+            if (frame.contentWindow !== e.source) { continue; }
+            sourceFrame = frame;
+            break;
+        }
+        if (sourceFrame === null) {
+            this._forwardFrameOffsetOrigin(null, uniqueId);
+            return;
+        }
+
+        const [forwardedX, forwardedY] = offset;
+        const {x, y} = sourceFrame.getBoundingClientRect();
+        offset = [forwardedX + x, forwardedY + y];
+
+        this._forwardFrameOffset(offset, uniqueId);
+    }
+
+    _forwardFrameOffsetParent(offset, uniqueId) {
+        window.parent.postMessage({action: 'getFrameOffset', params: {offset, uniqueId}}, '*');
+    }
+
+    _forwardFrameOffsetOrigin(offset, uniqueId) {
+        apiForward('frameOffset', {offset, uniqueId});
+    }
+}