Implement Cmd-Shift-D behaviour

package.json

@@ -239,7 +239,7 @@
                 "win": "ctrl+shift+d",
                 "linux": "ctrl+shift+d",
                 "key": "ctrl+shift+d",
-                "command": "editor.action.copyLinesDownAction",
+                "command": "extension.duplicate",
                 "when": "editorFocus"
             },
             {

src/actions.ts

@@ -0,0 +1,33 @@
+import * as vscode from "vscode";
+
+export function duplicateAction(editor: vscode.TextEditor) {
+    if (!hasActiveSelection(editor)) {
+        vscode.commands.executeCommand("editor.action.copyLinesDownAction");
+    } else {
+        duplicateWithSelection(editor);
+    }
+}
+
+function hasActiveSelection(editor: vscode.TextEditor): boolean {
+    for (var i = 0; i < editor.selections.length; i++) {
+        if (!editor.selections[i].isEmpty) {
+            return true;
+        }
+    }
+    return false;
+}
+
+function duplicateWithSelection(editor: vscode.TextEditor) {
+    var sel = editor.selection;
+    let text = editor.document.getText(sel)
+
+    editor.edit(edit => {
+        edit.insert(sel.active, text);
+    }).then(() => {
+        try {
+            editor.selection = new vscode.Selection(sel.active, editor.selection.active);
+        } catch (err) {
+            console.log(err)
+        }
+    })
+}

src/extension.ts

@@ -1,6 +1,7 @@
 import * as vscode from 'vscode';
 import { readFileAsync } from './fsWrapper';
 import { Mapper } from './mapper';
+import { duplicateAction } from './actions';
 import { ISetting, MappedSetting, CategorizedSettings, VscodeSetting } from './settings';
 import * as sublimeFolderFinder from './sublimeFolderFinder';
 import * as path from 'path';
@@ -14,6 +15,9 @@ export async function activate(context: vscode.ExtensionContext): Promise<void>
         await showPrompt();
         await context.globalState.update('alreadyPrompted', true);
     }
+
+    // register custom commands
+    context.subscriptions.push(vscode.commands.registerTextEditorCommand("extension.duplicate", duplicateAction));
 }
 
 async function showPrompt(): Promise<void> {