grid - reduce active change events when closing last editor in group

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

@@ -91,6 +91,7 @@ export interface IEditorGroupsAccessor {
 	getGroup(identifier: GroupIdentifier): IEditorGroupView;
 
 	activateGroup(identifier: IEditorGroupView | GroupIdentifier): IEditorGroupView;
+	activatePreviousActiveGroup();
 
 	addGroup(location: IEditorGroupView | GroupIdentifier, direction: GroupDirection, options?: IAddGroupOptions): IEditorGroupView;
 	mergeGroup(group: IEditorGroupView | GroupIdentifier, target: IEditorGroupView | GroupIdentifier, options?: IMergeGroupOptions): IEditorGroupView;

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

@@ -884,6 +884,18 @@ export class EditorGroupView extends Themable implements IEditorGroupView {
 		const editorToClose = this.activeEditor;
 		const editorHasFocus = isAncestor(document.activeElement, this.element);
 
+		// Optimization: if we are about to close the last editor in this group and settings
+		// are configured to close the group since it will be empty, we first set the last
+		// active group as empty before closing the editor. This reduces the amount of editor
+		// change events that this operation emits and will reduce flicker. Without this
+		// optimization, this group (if active) would first trigger a active editor change
+		// event because it became empty, only to then trigger another one when the next
+		// group gets active.
+		const closeEmptyGroup = this.accessor.partOptions.closeEmptyGroups;
+		if (closeEmptyGroup && this.active && this._group.count === 1) {
+			this.accessor.activatePreviousActiveGroup();
+		}
+
 		// Update model
 		this._group.closeEditor(editorToClose);
 
@@ -906,23 +918,22 @@ export class EditorGroupView extends Themable implements IEditorGroupView {
 			});
 		}
 
-		// Otherwise clear from editor control and send event
+		// Otherwise we are empty, so clear from editor control and send event
 		else {
 
 			// Forward to editor control
 			this.editorControl.closeEditor(editorToClose);
 
-			// Restore focus to group container as needed
-			if (editorHasFocus) {
+			// Restore focus to group container as needed unless group gets closed
+			if (editorHasFocus && !closeEmptyGroup) {
 				this.focus();
 			}
 
 			// Events
 			this._onDidGroupChange.fire({ kind: GroupChangeKind.EDITOR_ACTIVE });
 
-			// Check if group gets closed now
-			const closeGroup = this.isEmpty() && this.accessor.partOptions.closeEmptyGroups;
-			if (closeGroup) {
+			// Remove empty group if we should
+			if (closeEmptyGroup) {
 				this.accessor.removeGroup(this);
 			}
 		}

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

@@ -111,7 +111,7 @@ export class EditorPart extends Part implements IEditorGroupsService, IEditorGro
 		this.registerListeners();
 	}
 
-	//#region IEditorPartOptions
+	//#region IEditorGroupsAccessor
 
 	private enforcedPartOptions: IEditorPartOptions[] = [];
 
@@ -155,6 +155,14 @@ export class EditorPart extends Part implements IEditorGroupsService, IEditorGro
 		});
 	}
 
+	activatePreviousActiveGroup(): void {
+		const mostRecentlyActiveGroups = this.getGroups(GroupsOrder.MOST_RECENTLY_ACTIVE);
+		const previousActiveGroup = mostRecentlyActiveGroups[1];
+		if (previousActiveGroup) {
+			this.activateGroup(previousActiveGroup);
+		}
+	}
+
 	//#endregion
 
 	//#region IEditorGroupsService
@@ -478,9 +486,7 @@ export class EditorPart extends Part implements IEditorGroupsService, IEditorGro
 
 		// Activate next group if the removed one was active
 		if (this._activeGroup === groupView) {
-			const mostRecentlyActiveGroups = this.getGroups(GroupsOrder.MOST_RECENTLY_ACTIVE);
-			const nextActiveGroup = mostRecentlyActiveGroups[1]; // [0] will be the current group we are about to dispose
-			this.activateGroup(nextActiveGroup);
+			this.activatePreviousActiveGroup();
 		}
 
 		// Remove from grid widget & dispose