very first stacks model integration to editor open

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

@@ -38,7 +38,7 @@ import {ServiceCollection} from 'vs/platform/instantiation/common/serviceCollect
 import {IMessageService, IMessageWithAction, Severity} from 'vs/platform/message/common/message';
 import {ITelemetryService} from 'vs/platform/telemetry/common/telemetry';
 import {IProgressService} from 'vs/platform/progress/common/progress';
-import {EditorStacksModel} from 'vs/workbench/common/editor/editorStacksModel';
+import {EditorStacksModel, EditorGroup} from 'vs/workbench/common/editor/editorStacksModel';
 
 const EDITOR_STATE_STORAGE_KEY = 'editorpart.editorState';
 
@@ -417,11 +417,19 @@ export class EditorPart extends Part implements IEditorPart {
 				return editor;
 			}
 
+			const preserveFocus = options && options.preserveFocus;
+			const pinned = options && options.pinned;
+			const index = options && options.index;
+
 			// Focus (unless prevented)
-			if (!options || !options.preserveFocus) {
+			if (!preserveFocus) {
 				editor.focus();
 			}
 
+			// Update stacks
+			const group = this.ensureGroup(position, !preserveFocus);
+			group.openEditor(input, { active: true, pinned, index });
+
 			// Progress Done
 			this.sideBySideControl.updateProgress(position, ProgressState.DONE);
 
@@ -1022,4 +1030,17 @@ export class EditorPart extends Part implements IEditorPart {
 		array[to] = array[from];
 		array[from] = empty;
 	}
+
+	private ensureGroup(position: Position, activate = true): EditorGroup {
+		let group = this.stacksModel.groups[position];
+		if (!group) {
+			group = this.stacksModel.openGroup(position === Position.LEFT ? nls.localize('leftGroup', "Left") : position === Position.CENTER ? nls.localize('centerGroup', "Center") : nls.localize('rightGroup', "Right"), activate);
+		}
+
+		if (activate) {
+			this.stacksModel.setActive(group);
+		}
+
+		return group;
+	}
 }
\ No newline at end of file

src/vs/workbench/common/editor/editorStacksModel.ts

@@ -696,6 +696,10 @@ export class EditorStacksModel implements IEditorStacksModel {
 	}
 
 	public setActive(group: EditorGroup): void {
+		if (this.active === group) {
+			return;
+		}
+
 		this.active = group;
 
 		this._onGroupActivated.fire(this.active);