void MainCanvas_MouseWheel(object sender, MouseWheelEventArgs e)
{
const double ScaleRate = 1.1;
Point mouseAtMainCanvas = e.GetPosition(MainCanvas);
Point mouseAtScrollViewer = e.GetPosition(MainScrollViewer);
ScaleTransform st = MainCanvas.LayoutTransform as ScaleTransform;
if (e.Delta > 0 && st.ScaleX < 64)
{
st.ScaleX = st.ScaleY = st.ScaleX * ScaleRate;
}
else if (st.ScaleX > 0.2)
{
st.ScaleX = st.ScaleY = st.ScaleX / ScaleRate;
}
MainScrollViewer.ScrollToHorizontalOffset(0);
MainScrollViewer.ScrollToVerticalOffset(0);
UpdateLayout();
Vector offset = MainCanvas.TranslatePoint(mouseAtMainCanvas, MainScrollViewer) - mouseAtScrollViewer;
MainScrollViewer.ScrollToHorizontalOffset(offset.X);
MainScrollViewer.ScrollToVerticalOffset(offset.Y);
UpdateLayout();
e.Handled = true;
}
private void MainScrollViewer_MouseMove(object sender, MouseEventArgs e)
{
Cursor = Cursors.Arrow;
if (e.MiddleButton == MouseButtonState.Pressed)
{
MainScrollViewer.ScrollToHorizontalOffset(MainScrollViewer.HorizontalOffset + MiddleMousePressPoint.X - e.GetPosition(MainScrollViewer).X);
MainScrollViewer.ScrollToVerticalOffset(MainScrollViewer.VerticalOffset + MiddleMousePressPoint.Y - e.GetPosition(MainScrollViewer).Y);
MiddleMousePressPoint = e.GetPosition(MainScrollViewer);
Cursor = Cursors.ScrollAll;
}
}
void OnMouseMove(object sender, MouseEventArgs e)
{
if (lastDragPoint.HasValue)
{
Point posNow = e.GetPosition(MainScrollViewer);
double dX = posNow.X - lastDragPoint.Value.X;
double dY = posNow.Y - lastDragPoint.Value.Y;
lastDragPoint = posNow;
MainScrollViewer.ScrollToHorizontalOffset(MainScrollViewer.HorizontalOffset - dX);
MainScrollViewer.ScrollToVerticalOffset(MainScrollViewer.VerticalOffset - dY);
}
}
void OnScrollViewerScrollChanged(object sender, ScrollChangedEventArgs e)
{
if (e.ExtentHeightChange != 0 || e.ExtentWidthChange != 0)
{
Point?targetBefore = null;
Point?targetNow = null;
if (!lastMousePositionOnTarget.HasValue)
{
if (lastCenterPositionOnTarget.HasValue)
{
var centerOfViewport = new Point(MainScrollViewer.ViewportWidth / 2, MainScrollViewer.ViewportHeight / 2);
Point centerOfTargetNow = MainScrollViewer.TranslatePoint(centerOfViewport, MainCanvas);
targetBefore = lastCenterPositionOnTarget;
targetNow = centerOfTargetNow;
}
}
else
{
targetBefore = lastMousePositionOnTarget;
targetNow = Mouse.GetPosition(MainCanvas);
lastMousePositionOnTarget = null;
}
if (targetBefore.HasValue)
{
double dXInTargetPixels = targetNow.Value.X - targetBefore.Value.X;
double dYInTargetPixels = targetNow.Value.Y - targetBefore.Value.Y;
double multiplicatorX = e.ExtentWidth / MainCanvas.Width;
double multiplicatorY = e.ExtentHeight / MainCanvas.Height;
double newOffsetX = MainScrollViewer.HorizontalOffset - dXInTargetPixels * multiplicatorX;
double newOffsetY = MainScrollViewer.VerticalOffset - dYInTargetPixels * multiplicatorY;
if (double.IsNaN(newOffsetX) || double.IsNaN(newOffsetY))
{
return;
}
MainScrollViewer.ScrollToHorizontalOffset(newOffsetX);
MainScrollViewer.ScrollToVerticalOffset(newOffsetY);
}
}
}
private void ViewCenter()
{
MainScrollViewer.ScrollToHorizontalOffset(MainCanvas.ActualWidth / 2 - 450);
}