RestrictedViewportLimiter.java

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package viewer.ganttchart;

import com.yworks.yfiles.geometry.RectD;
import com.yworks.yfiles.view.CanvasControl;
import com.yworks.yfiles.view.GraphControl;
import com.yworks.yfiles.view.ViewportLimiter;
import com.yworks.yfiles.view.ViewportLimitingPolicy;

/**
 * Prevents scrolling above or below the vertical bounds of the task lanes.
 */
public class RestrictedViewportLimiter extends ViewportLimiter {
  private final GraphControl taskControl;

  /**
   * Initializes a new {@code RestrictedViewportLimiter} instances.
   */
  public RestrictedViewportLimiter( GraphControl taskControl ) {
    this.taskControl = taskControl;
  }

  /**
   * Limits the viewport to the area which contains task nodes.
   * @param canvas The canvas control on which the viewport should be applied.
   * @param suggestedViewport The suggested viewport.
   * @param forceStrictLimits Whether to force {@link ViewportLimitingPolicy#STRICT} limiting. Passing {@code true} overrides the
   * {@link #getLimitingPolicy() LimitingPolicy}. This is used for example by {@link CanvasComponent#fitContent(boolean)}
   * or ZoomToCurrentItemCommand where larger viewport changes are expected.
   */
  @Override
  public RectD limitViewport( CanvasControl canvas, RectD suggestedViewport, boolean forceStrictLimits ) {
    double topY = taskControl.getContentRect().getY();
    double bottomY = taskControl.getContentRect().getMaxY();

    double oldY = suggestedViewport.getY();
    double newY = Math.max(topY, Math.min(bottomY - suggestedViewport.getHeight(), oldY));

    return new RectD(suggestedViewport.getX(), newY, suggestedViewport.getWidth(), suggestedViewport.getHeight());
  }
}