src/vs/workbench/browser/parts/panel/panelPart.ts/PanelPart/onPanelOpen
class PanelPart:	private onPanelOpen(panel: IPanel): void {
		this.activePanelContextKey.set(panel.getId());

		const foundPanel = this.panelRegistry.getPanel(panel.getId());
		if (foundPanel) {
			this.compositeBar.addComposite(foundPanel);
		}

		// Activate composite when opened
		this.compositeBar.activateComposite(panel.getId());

		const panelDescriptor = this.panelRegistry.getPanel(panel.getId());
		if (panelDescriptor) {
			const viewContainer = this.getViewContainer(panelDescriptor.id);
			if (viewContainer?.hideIfEmpty) {
				const viewContainerModel = this.viewDescriptorService.getViewContainerModel(viewContainer);
				if (viewContainerModel.activeViewDescriptors.length === 0 && this.compositeBar.getPinnedComposites().length > 1) {
					this.hideComposite(panelDescriptor.id); // Update the composite bar by hiding
				}
			}
		}

		this.layoutCompositeBar(); // Need to relayout composite bar since different panels have different action bar width
		this.layoutEmptyMessage();
	}