/// <summary>Mouse/key events on the chart</summary>
protected override void OnMouseDown(MouseButtonEventArgs args)
{
//
// *** Use PreviewMouseDown to set pending MouseOps ***
// *** Don't set e.Handled = true, SetPending() is enough ***
//
// Notes:
// - MouseButton events in WPF are routed events that behave differently to WinForms.
// - The order of handlers for MouseDown is:
// 1) Registered class handlers
// 2) OnMouseDown - base.OnMouseDown() does *not* raise the MouseDown event
// 3) Handers attached to event MouseDown
// - MouseDown is a 'bubbling' event, it starts at the visual tree leaf element and
// bubble up the tree, stopped when a handle sets 'e.Handled = true'
// - PreviewMouseDown is a tunnelling 'event', it starts at the window and drills
// down the tree to the leaves. If 'e.Handled = true' in a PreviewMouseDown handler
// then MouseDown is never raised, and override OnMouseDown isn't called.
base.OnMouseDown(args);
var location = args.GetPosition(this);
// If a mouse op is already active, ignore mouse down
if (MouseOperations.Active != null)
{
return;
}
// Look for the mouse op to perform
if (MouseOperations.Pending[args.ChangedButton] == null && DefaultMouseControl)
{
switch (args.ChangedButton)
{
default: return;
case MouseButton.Left: MouseOperations.Pending[args.ChangedButton] = new MouseOpDefaultLButton(this); break;
case MouseButton.Middle: MouseOperations.Pending[args.ChangedButton] = new MouseOpDefaultMButton(this); break;
case MouseButton.Right: MouseOperations.Pending[args.ChangedButton] = new MouseOpDefaultRButton(this); break;
case MouseButton.XButton1: UndoNavigation(); break;
case MouseButton.XButton2: RedoNavigation(); break;
}
}
// Start the next mouse op
MouseOperations.BeginOp(args.ChangedButton);
// Get the mouse op, save mouse location and hit test data, then call op.MouseDown()
var op = MouseOperations.Active;
if (op != null && !op.Cancelled)
{
// Don't capture the mouse here in mouse down because that prevents
// mouse up messages getting to subscribers of the MouseUp event.
// Only capture the mouse when we know it's a drag operation.
op.GrabClient = op.DropClient = location; // Note: in ChartControl space, not ChartPanel space
op.GrabChart = op.DropChart = ClientToChart(location);
op.HitResult = HitTestCS(op.GrabClient, Keyboard.Modifiers, args.ToMouseBtns(), null);
op.MouseDown(args);
}
}
