Class MiddleColumnView

packages/dockview-core/src/dockview/dockviewShell.ts:237–359

* The vertical centre column: top (optional) | center | bottom (optional). * This view sits between the left and right edge panels in the outer * horizontal splitview, so its primary axis is width (horizontal).

 * horizontal splitview, so its primary axis is width (horizontal).
 */
class MiddleColumnView implements IView, IDisposable {
    private readonly _element: HTMLElement;
    private readonly _splitview: Splitview;
    private readonly _onDidChange = new Emitter<{
        size?: number;
        orthogonalSize?: number;
    }>();

    readonly onDidChange: Event<{ size?: number; orthogonalSize?: number }> =
        this._onDidChange.event;
    readonly minimumSize = 100;
    readonly maximumSize = Number.POSITIVE_INFINITY;
    readonly priority = LayoutPriority.High;

    private _topIndex: number | undefined;
    private _centerIndex: number;
    private _bottomIndex: number | undefined;

    get element(): HTMLElement {
        return this._element;
    }

    constructor(centerView: CenterView, gap = 0) {
        this._element = document.createElement('div');
        this._element.className = 'dv-shell-middle-column';
        this._element.style.height = '100%';
        this._element.style.width = '100%';

        this._splitview = new Splitview(this._element, {
            orientation: Orientation.VERTICAL,
            proportionalLayout: false,
            margin: gap,
        });

        this._centerIndex = 0;
        this._splitview.addView(centerView, { type: 'distribute' }, 0);
    }

    addTopView(view: EdgeGroupView, initialSize: number): void {
        // Insert before center
        this._splitview.addView(view, initialSize, 0);
        this._topIndex = 0;
        this._centerIndex += 1;
        if (this._bottomIndex !== undefined) {
            this._bottomIndex += 1;
        }
    }

    addBottomView(view: EdgeGroupView, initialSize: number): void {
        // Append after center (and any existing bottom — shouldn't happen but safe)
        const newIndex = this._splitview.length;
        this._splitview.addView(view, initialSize, newIndex);
        this._bottomIndex = newIndex;
    }

    removeView(position: 'top' | 'bottom'): void {
        const index = position === 'top' ? this._topIndex : this._bottomIndex;
        if (index === undefined) {