source: branches/HeuristicLab.Problems.GrammaticalOptimization/DynamicDataDisplay/Charts/Navigation/TouchPadScroll.cs @ 13398

using System;
using System.Windows;
using System.Windows.Input;
using System.Windows.Interop;


namespace Microsoft.Research.DynamicDataDisplay.Navigation
{
    /// <summary>This class allows convenient navigation around viewport using touchpad on
    /// some notebooks</summary>
  public sealed class TouchpadScroll : NavigationBase {
    public TouchpadScroll() {
      Loaded += OnLoaded;
    }

    private void OnLoaded(object sender, RoutedEventArgs e) {
      WindowInteropHelper helper = new WindowInteropHelper(Window.GetWindow(this));
      HwndSource source = HwndSource.FromHwnd(helper.Handle);
      source.AddHook(OnMessageAppeared);
    }

    private IntPtr OnMessageAppeared(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled) {
      if (msg == WindowsMessages.WM_MOUSEWHEEL) {
        Point mousePos = MessagesHelper.GetMousePosFromLParam(lParam);
        mousePos = TranslatePoint(mousePos, this);

        if (Viewport.Output.Contains(mousePos)) {
          MouseWheelZoom(MessagesHelper.GetMousePosFromLParam(lParam), MessagesHelper.GetWheelDataFromWParam(wParam));
          handled = true;
        }
      }
      return IntPtr.Zero;
    }

    double wheelZoomSpeed = 1.2;
    public double WheelZoomSpeed {
      get { return wheelZoomSpeed; }
      set { wheelZoomSpeed = value; }
    }

    private void MouseWheelZoom(Point mousePos, int wheelRotationDelta) {
      Point zoomTo = mousePos.ScreenToData(Viewport.Transform);

      double zoomSpeed = Math.Abs(wheelRotationDelta / Mouse.MouseWheelDeltaForOneLine);
      zoomSpeed *= wheelZoomSpeed;
      if (wheelRotationDelta < 0) {
        zoomSpeed = 1 / zoomSpeed;
      }
      Viewport.Visible = Viewport.Visible.Zoom(zoomTo, zoomSpeed);
    }
  }
}