src/vs/workbench/browser/layout.ts/Layout/getMaximumEditorDimensions
class Layout:	getMaximumEditorDimensions(): Dimension {
		const panelPosition = this.getPanelPosition();
		const isColumn = panelPosition === Position.RIGHT || panelPosition === Position.LEFT;
		const takenWidth =
			(this.isVisible(Parts.ACTIVITYBAR_PART) ? this.activityBarPartView.minimumWidth : 0) +
			(this.isVisible(Parts.SIDEBAR_PART) ? this.sideBarPartView.minimumWidth : 0) +
			(this.isVisible(Parts.PANEL_PART) && isColumn ? this.panelPartView.minimumWidth : 0) +
			(this.isVisible(Parts.AUXILIARYBAR_PART) ? this.auxiliaryBarPartView.minimumWidth : 0);

		const takenHeight =
			(this.isVisible(Parts.TITLEBAR_PART) ? this.titleBarPartView.minimumHeight : 0) +
			(this.isVisible(Parts.STATUSBAR_PART) ? this.statusBarPartView.minimumHeight : 0) +
			(this.isVisible(Parts.PANEL_PART) && !isColumn ? this.panelPartView.minimumHeight : 0);

		const availableWidth = this.dimension.width - takenWidth;
		const availableHeight = this.dimension.height - takenHeight;

		return new Dimension(availableWidth, availableHeight);
	}