DND: allow to copy a tab to a new group instead of moving

src/vs/workbench/browser/parts/editor/tabsTitleControl.ts

@@ -13,9 +13,10 @@ import {prepareActions} from 'vs/workbench/browser/actionBarRegistry';
 import arrays = require('vs/base/common/arrays');
 import errors = require('vs/base/common/errors');
 import DOM = require('vs/base/browser/dom');
+import {isMacintosh} from 'vs/base/common/platform';
 import {Builder, $} from 'vs/base/browser/builder';
 import {MIME_BINARY} from 'vs/base/common/mime';
-import {IEditorGroup, IEditorIdentifier, asFileEditorInput} from 'vs/workbench/common/editor';
+import {IEditorGroup, IEditorIdentifier, asFileEditorInput, EditorOptions} from 'vs/workbench/common/editor';
 import {ToolBar} from 'vs/base/browser/ui/toolbar/toolbar';
 import {StandardKeyboardEvent} from 'vs/base/browser/keyboardEvent';
 import {CommonKeybindings} from 'vs/base/common/keyCodes';
@@ -126,9 +127,17 @@ export class TabsTitleControl extends TitleControl {
 
 						const sourcePosition = this.stacks.positionOfGroup(TabsTitleControl.draggedEditor.group);
 						const targetPosition = this.stacks.positionOfGroup(group);
+						const targetIndex = group.count;
 
-						// Move editor to target position at the end
-						this.editorGroupService.moveEditor(TabsTitleControl.draggedEditor.editor, sourcePosition, targetPosition, group.count);
+						// Move editor to target position and index
+						if (this.isMoveOperation(e, TabsTitleControl.draggedEditor.group, group)) {
+							this.editorGroupService.moveEditor(TabsTitleControl.draggedEditor.editor, sourcePosition, targetPosition, targetIndex);
+						}
+
+						// Copy: just open editor at target index
+						else {
+							this.editorService.openEditor(TabsTitleControl.draggedEditor.editor, EditorOptions.create({ pinned: true, index: targetIndex }), targetPosition).done(null, errors.onUnexpectedError);
+						}
 					}
 				}
 			}
@@ -387,7 +396,7 @@ export class TabsTitleControl extends TitleControl {
 		this.tabDisposeables.push(DOM.addDisposableListener(tab, DOM.EventType.DRAG_START, (e: DragEvent) => {
 			DOM.addClass(tab, 'dragged');
 			TabsTitleControl.draggedEditor = { editor, group };
-			e.dataTransfer.effectAllowed = 'move';
+			e.dataTransfer.effectAllowed = 'copyMove';
 
 			// Enable support to drag a file to desktop
 			const fileInput = asFileEditorInput(editor, true);
@@ -423,11 +432,24 @@ export class TabsTitleControl extends TitleControl {
 				const targetIndex = group.indexOf(editor);
 
 				// Move editor to target position and index
-				this.editorGroupService.moveEditor(TabsTitleControl.draggedEditor.editor, sourcePosition, targetPosition, targetIndex);
+				if (this.isMoveOperation(e, TabsTitleControl.draggedEditor.group, group)) {
+					this.editorGroupService.moveEditor(TabsTitleControl.draggedEditor.editor, sourcePosition, targetPosition, targetIndex);
+				}
+
+				// Copy: just open editor at target index
+				else {
+					this.editorService.openEditor(TabsTitleControl.draggedEditor.editor, EditorOptions.create({ pinned: true, index: targetIndex }), targetPosition).done(null, errors.onUnexpectedError);
+				}
 			}
 		}));
 	}
 
+	private isMoveOperation(e: DragEvent, source: IEditorGroup, target: IEditorGroup) {
+		const isCopy = (e.ctrlKey && !isMacintosh) || (e.altKey && isMacintosh);
+
+		return !isCopy || source.id === target.id;
+	}
+
 	private getTabActions(identifier: IEditorIdentifier): IAction[] {
 		const {editor, group} = identifier;