1 files changed, 149 insertions, 0 deletions
diff --git a/ext/fg/js/text-source-range.js b/ext/fg/js/text-source-range.js
new file mode 100644
index 00000000..86a57ae1
--- /dev/null
+++ b/ext/fg/js/text-source-range.js
@@ -0,0 +1,149 @@
+/*
+ * Copyright (C) 2016-2020  Yomichan Authors
+ *
+ * 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
+ * DOMTextScanner
+ */
+
+class TextSourceRange {
+    constructor(range, content, imposterContainer, imposterSourceElement) {
+        this.range = range;
+        this.rangeStartOffset = range.startOffset;
+        this.content = content;
+        this.imposterContainer = imposterContainer;
+        this.imposterSourceElement = imposterSourceElement;
+    }
+
+    get startOffset() {
+        return this.range.startOffset;
+    }
+
+    get endOffset() {
+        return this.range.endOffset;
+    }
+
+    clone() {
+        return new TextSourceRange(this.range.cloneRange(), this.content, this.imposterContainer, this.imposterSourceElement);
+    }
+
+    cleanup() {
+        if (this.imposterContainer !== null && this.imposterContainer.parentNode !== null) {
+            this.imposterContainer.parentNode.removeChild(this.imposterContainer);
+        }
+    }
+
+    text() {
+        return this.content;
+    }
+
+    setEndOffset(length, layoutAwareScan, fromEnd=false) {
+        const state = (
+            fromEnd ?
+            new DOMTextScanner(this.range.endContainer, this.range.endOffset, !layoutAwareScan, layoutAwareScan).seek(length) :
+            new DOMTextScanner(this.range.startContainer, this.range.startOffset, !layoutAwareScan, layoutAwareScan).seek(length)
+        );
+        this.range.setEnd(state.node, state.offset);
+        this.content = (fromEnd ? this.content + state.content : state.content);
+        return length - state.remainder;
+    }
+
+    setStartOffset(length, layoutAwareScan) {
+        const state = new DOMTextScanner(this.range.startContainer, this.range.startOffset, !layoutAwareScan, layoutAwareScan).seek(-length);
+        this.range.setStart(state.node, state.offset);
+        this.rangeStartOffset = this.range.startOffset;
+        this.content = state.content + this.content;
+        return length - state.remainder;
+    }
+
+    getRect() {
+        return this.range.getBoundingClientRect();
+    }
+
+    getWritingMode() {
+        return TextSourceRange.getElementWritingMode(TextSourceRange.getParentElement(this.range.startContainer));
+    }
+
+    select() {
+        const selection = window.getSelection();
+        selection.removeAllRanges();
+        selection.addRange(this.range);
+    }
+
+    deselect() {
+        const selection = window.getSelection();
+        selection.removeAllRanges();
+    }
+
+    equals(other) {
+        if (!(
+            typeof other === 'object' &&
+            other !== null &&
+            other instanceof TextSourceRange
+        )) {
+            return false;
+        }
+        if (this.imposterSourceElement !== null) {
+            return (
+                this.imposterSourceElement === other.imposterSourceElement &&
+                this.rangeStartOffset === other.rangeStartOffset
+            );
+        } else {
+            try {
+                return this.range.compareBoundaryPoints(Range.START_TO_START, other.range) === 0;
+            } catch (e) {
+                if (e.name === 'WrongDocumentError') {
+                    // This can happen with shadow DOMs if the ranges are in different documents.
+                    return false;
+                }
+                throw e;
+            }
+        }
+    }
+
+    static getParentElement(node) {
+        while (node !== null && node.nodeType !== Node.ELEMENT_NODE) {
+            node = node.parentNode;
+        }
+        return node;
+    }
+
+    static getElementWritingMode(element) {
+        if (element !== null) {
+            const style = window.getComputedStyle(element);
+            const writingMode = style.writingMode;
+            if (typeof writingMode === 'string') {
+                return TextSourceRange.normalizeWritingMode(writingMode);
+            }
+        }
+        return 'horizontal-tb';
+    }
+
+    static normalizeWritingMode(writingMode) {
+        switch (writingMode) {
+            case 'lr':
+            case 'lr-tb':
+            case 'rl':
+                return 'horizontal-tb';
+            case 'tb':
+                return 'vertical-lr';
+            case 'tb-rl':
+                return 'vertical-rl';
+            default:
+                return writingMode;
+        }
+    }
+}