extensions/image-preview/src/preview.ts/Preview/update
class Preview:	private update() {
		if (this._previewState === PreviewState.Disposed) {
			return;
		}

		if (this.webviewEditor.active) {
			this._previewState = PreviewState.Active;
			this.sizeStatusBarEntry.show(this.id, this._imageSize || '');
			this.binarySizeStatusBarEntry.show(this.id, this._imageBinarySize);
			this.zoomStatusBarEntry.show(this.id, this._imageZoom || 'fit');
		} else {
			if (this._previewState === PreviewState.Active) {
				this.sizeStatusBarEntry.hide(this.id);
				this.binarySizeStatusBarEntry.hide(this.id);
				this.zoomStatusBarEntry.hide(this.id);
			}
			this._previewState = PreviewState.Visible;
		}
	}