private void MainGrid_MouseDown(object sender, MouseButtonEventArgs e)
{
previousMousePosition = e.GetPosition(mainGrid);
// Reverse-transform mouse grid coordinates (screen) into Canvas coordinates
Matrix m = mainMatrixTransform.Matrix;
m.Invert();
var mouseT = m.Transform(previousMousePosition);
pmm = null;
isMovingMode = false;
foreach (var gsSource in b.AllStacks())
{
movingGroup = gsSource.FromHitTest(mouseT);
if (movingGroup != null)
{
Point P1 = movingGroup.GetTopLeft();
StartingPoint = P1;
Vector v = P1 - mouseT;
// A closure to be executed my MouseMoveWhenDown with mouse coordinates (in game space) as parameter P
pmm = P =>
{
movingGroup.SetTopLeft(P + v);
movingGroup.ToStack = null; // Reset in case mouse is moving away from a potential drop target
foreach (var gsTarget in b.AllStacks())
{
if (gsTarget != movingGroup.FromStack)
{
if (gsTarget.ToHitTest(P, movingGroup))
{
movingGroup.ToStack = gsTarget;
}
}
}
};
// Be sure to call GetPosition before Capture, otherwise GetPosition returns 0 after Capture
// Capture to get MouseUp event raised by grid
Mouse.Capture(mainGrid);
mainGrid.MouseMove -= new MouseEventHandler(MainGrid_MouseMoveWhenUp);
mainGrid.MouseMove += new MouseEventHandler(MainGrid_MouseMoveWhenDown);
return;
}
}
// Clicked outside active and valid area
movingGroup = null;
}