feat(mdviewer): copy/cut/paste row and column in table context menus

Add Copy row, Cut row, Paste row, Copy column, Cut column, Paste column
items to both the right-click context menu and the row/column handle
menus. The clipboard is module-level (lasts the session) and stores
cell HTML so styling is preserved on paste.

Paste items only appear when their respective clipboard has content.
Cut row is disabled for header rows.

Author: abose

src-mdviewer/src/components/editor.js

@@ -735,6 +735,67 @@ function deleteTableColumn(table, colIdx) {
     });
 }
 
+// Module-level clipboard for table row/column copy-paste.
+// Stores the inner HTML of each cell so they can be re-inserted into other rows/cols.
+let _tableRowClipboard = null;   // { cells: [html, ...] }
+let _tableColClipboard = null;   // { cells: [html, ...] }  one per row in source table
+
+function copyTableRow(tr) {
+    _tableRowClipboard = {
+        cells: Array.from(tr.children).map(td => td.innerHTML)
+    };
+}
+
+function copyTableColumn(table, colIdx) {
+    const rows = table.querySelectorAll("tr");
+    _tableColClipboard = {
+        cells: Array.from(rows).map(row => {
+            const cell = row.children[colIdx];
+            return cell ? cell.innerHTML : "";
+        })
+    };
+}
+
+function pasteTableRow(table, afterRow) {
+    if (!_tableRowClipboard) return;
+    const tbody = table.querySelector("tbody") || table;
+    const refRow = afterRow || tbody.lastElementChild;
+    const colCount = refRow ? refRow.children.length : _tableRowClipboard.cells.length;
+    const newRow = document.createElement("tr");
+    for (let i = 0; i < colCount; i++) {
+        const td = document.createElement("td");
+        td.innerHTML = _tableRowClipboard.cells[i] != null ? _tableRowClipboard.cells[i] : "&nbsp;";
+        newRow.appendChild(td);
+    }
+    if (afterRow && afterRow.nextSibling) {
+        afterRow.parentNode.insertBefore(newRow, afterRow.nextSibling);
+    } else if (afterRow) {
+        afterRow.parentNode.appendChild(newRow);
+    } else {
+        tbody.appendChild(newRow);
+    }
+    focusCell(newRow.firstElementChild);
+    return newRow;
+}
+
+function pasteTableColumn(table, afterColIdx) {
+    if (!_tableColClipboard) return;
+    const rows = table.querySelectorAll("tr");
+    const insertIdx = afterColIdx != null ? afterColIdx + 1 : (rows[0]?.children.length || 0);
+    rows.forEach((row, rowIdx) => {
+        const isHeader = row.parentElement.tagName === "THEAD";
+        const cell = document.createElement(isHeader ? "th" : "td");
+        const html = _tableColClipboard.cells[rowIdx];
+        cell.innerHTML = (html != null && html !== "") ? html : (isHeader ? t("table.header") : "&nbsp;");
+        const refCell = row.children[insertIdx];
+        if (refCell) {
+            row.insertBefore(cell, refCell);
+        } else {
+            row.appendChild(cell);
+        }
+    });
+}
+
 function deleteTable(table) {
     const wrapper = table.closest(".table-wrapper");
     const target = wrapper || table;
@@ -858,6 +919,10 @@ function showHandleMenu(anchor, type, ctx, contentEl, wrapper, clickX) {
             { label: t("table.insert_row_above"), action: () => { flushSnapshot(contentEl); addTableRow(ctx.table, null, ctx.tr); dispatchInputEvent(contentEl); } },
             { label: t("table.insert_row_below"), action: () => { flushSnapshot(contentEl); addTableRow(ctx.table, ctx.tr); dispatchInputEvent(contentEl); } },
             { divider: true },
+            { label: t("table.copy_row"), action: () => { copyTableRow(ctx.tr); } },
+            { label: t("table.cut_row"), disabled: ctx.isHeader, action: () => { flushSnapshot(contentEl); copyTableRow(ctx.tr); deleteTableRow(ctx.table, ctx.tr); dispatchInputEvent(contentEl); } },
+            ...(_tableRowClipboard ? [{ label: t("table.paste_row"), action: () => { flushSnapshot(contentEl); pasteTableRow(ctx.table, ctx.tr); dispatchInputEvent(contentEl); } }] : []),
+            { divider: true },
             { label: t("table.delete_row"), destructive: true, disabled: ctx.isHeader, action: () => { flushSnapshot(contentEl); deleteTableRow(ctx.table, ctx.tr); dispatchInputEvent(contentEl); } },
             { divider: true },
             { label: t("table.delete_table"), destructive: true, action: () => { flushSnapshot(contentEl); deleteTable(ctx.table); dispatchInputEvent(contentEl); } }
@@ -867,6 +932,10 @@ function showHandleMenu(anchor, type, ctx, contentEl, wrapper, clickX) {
             { label: t("table.insert_col_left"), action: () => { flushSnapshot(contentEl); addTableColumn(ctx.table, ctx.colIdx - 1); dispatchInputEvent(contentEl); } },
             { label: t("table.insert_col_right"), action: () => { flushSnapshot(contentEl); addTableColumn(ctx.table, ctx.colIdx); dispatchInputEvent(contentEl); } },
             { divider: true },
+            { label: t("table.copy_col"), action: () => { copyTableColumn(ctx.table, ctx.colIdx); } },
+            { label: t("table.cut_col"), action: () => { flushSnapshot(contentEl); copyTableColumn(ctx.table, ctx.colIdx); deleteTableColumn(ctx.table, ctx.colIdx); dispatchInputEvent(contentEl); } },
+            ...(_tableColClipboard ? [{ label: t("table.paste_col"), action: () => { flushSnapshot(contentEl); pasteTableColumn(ctx.table, ctx.colIdx); dispatchInputEvent(contentEl); } }] : []),
+            { divider: true },
             { label: t("table.delete_col"), destructive: true, action: () => { flushSnapshot(contentEl); deleteTableColumn(ctx.table, ctx.colIdx); dispatchInputEvent(contentEl); } },
             { divider: true },
             { label: t("table.delete_table"), destructive: true, action: () => { flushSnapshot(contentEl); deleteTable(ctx.table); dispatchInputEvent(contentEl); } }
@@ -1091,6 +1160,14 @@ function showTableContextMenu(x, y, ctx, contentEl) {
         { label: t("table.add_col_left"), action: () => { flushSnapshot(contentEl); addTableColumn(ctx.table, ctx.colIdx - 1); dispatchInputEvent(contentEl); } },
         { label: t("table.add_col_right"), action: () => { flushSnapshot(contentEl); addTableColumn(ctx.table, ctx.colIdx); dispatchInputEvent(contentEl); } },
         { divider: true },
+        { label: t("table.copy_row"), action: () => { copyTableRow(ctx.tr); } },
+        { label: t("table.cut_row"), action: () => { flushSnapshot(contentEl); copyTableRow(ctx.tr); deleteTableRow(ctx.table, ctx.tr); dispatchInputEvent(contentEl); } },
+        ...(_tableRowClipboard ? [{ label: t("table.paste_row"), action: () => { flushSnapshot(contentEl); pasteTableRow(ctx.table, ctx.tr); dispatchInputEvent(contentEl); } }] : []),
+        { divider: true },
+        { label: t("table.copy_col"), action: () => { copyTableColumn(ctx.table, ctx.colIdx); } },
+        { label: t("table.cut_col"), action: () => { flushSnapshot(contentEl); copyTableColumn(ctx.table, ctx.colIdx); deleteTableColumn(ctx.table, ctx.colIdx); dispatchInputEvent(contentEl); } },
+        ...(_tableColClipboard ? [{ label: t("table.paste_col"), action: () => { flushSnapshot(contentEl); pasteTableColumn(ctx.table, ctx.colIdx); dispatchInputEvent(contentEl); } }] : []),
+        { divider: true },
         { label: t("table.delete_row"), destructive: true, action: () => { flushSnapshot(contentEl); deleteTableRow(ctx.table, ctx.tr); dispatchInputEvent(contentEl); } },
         { label: t("table.delete_col"), destructive: true, action: () => { flushSnapshot(contentEl); deleteTableColumn(ctx.table, ctx.colIdx); dispatchInputEvent(contentEl); } },
         { divider: true },

src-mdviewer/src/locales/en.json

@@ -161,6 +161,12 @@
     "add_row_below": "Add row below",
     "add_col_left": "Add column left",
     "add_col_right": "Add column right",
+    "copy_row": "Copy row",
+    "cut_row": "Cut row",
+    "paste_row": "Paste row below",
+    "copy_col": "Copy column",
+    "cut_col": "Cut column",
+    "paste_col": "Paste column right",
     "delete_table": "Delete table"
   },
   "dialog": {