message: Using BackgroundColorSide instead of boolean
diff: @@ -69,6 +69,11 @@ export interface PriceScaleOnPane {
  pane: Pane;
  }
  +const enum BackgroundColorSide {
  + Top,
  + Bottom,
  +}
  +
  type InvalidateHandler = (mask: InvalidateMask) => void;
  export type VisiblePriceScaleOptions = PriceScaleOptions;
  @@ -166,8 +171,8 @@ export class ChartModel implements IDestroyable {
  this.createPane();
  this._panes[0].setStretchFactor(DEFAULT_STRETCH_FACTOR * 2);
  - this._backgroundTopColor = this._getBackgroundColor(true);
  - this._backgroundBottomColor = this._getBackgroundColor(false);
  + this._backgroundTopColor = this._getBackgroundColor(BackgroundColorSide.Top);
  + this._backgroundBottomColor = this._getBackgroundColor(BackgroundColorSide.Bottom);
  }
  public fullUpdate(): void {
  @@ -219,8 +224,8 @@ export class ChartModel implements IDestroyable {
  this._priceScalesOptionsChanged.fire();
  }
  - this._backgroundTopColor = this._getBackgroundColor(true);
  - this._backgroundBottomColor = this._getBackgroundColor(false);
  + this._backgroundTopColor = this._getBackgroundColor(BackgroundColorSide.Top);
  + this._backgroundBottomColor = this._getBackgroundColor(BackgroundColorSide.Bottom);
  this.fullUpdate();
  }
  @@ -700,11 +705,13 @@ export class ChartModel implements IDestroyable {
  return series;
  }
  - private _getBackgroundColor(top: boolean): string {
  + private _getBackgroundColor(side: BackgroundColorSide): string {
  const layoutOptions = this._options.layout;
  if (layoutOptions.backgroundType === ColorType.Gradient) {
  - return top ? layoutOptions.backgroundGradientStartColor : layoutOptions.backgroundGradientEndColor;
  + return side === BackgroundColorSide.Top ?
  + layoutOptions.backgroundGradientStartColor :
  + layoutOptions.backgroundGradientEndColor;
  }
  return layoutOptions.backgroundColor;
  