ZoomBox.cs
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using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Media;
namespace RoboforkApp
{
public class ZoomBox : Control
{
private Thumb zoomThumb;
private Canvas zoomCanvas;
private Slider zoomSlider;
private ScaleTransform scaleTransform;
private DesignerCanvas designerCanvas;
public ScrollViewer ScrollViewer
{
get { return (ScrollViewer)GetValue(ScrollViewerProperty); }
set { SetValue(ScrollViewerProperty, value); }
}
public static readonly DependencyProperty ScrollViewerProperty =
DependencyProperty.Register("ScrollViewer", typeof(ScrollViewer), typeof(ZoomBox));
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
if (this.ScrollViewer == null)
return;
this.designerCanvas = this.ScrollViewer.Content as DesignerCanvas;
if (this.designerCanvas == null)
throw new Exception("DesignerCanvas must not be null!");
this.zoomThumb = Template.FindName("PART_ZoomThumb", this) as Thumb;
if (this.zoomThumb == null)
throw new Exception("PART_ZoomThumb template is missing!");
this.zoomCanvas = Template.FindName("PART_ZoomCanvas", this) as Canvas;
if (this.zoomCanvas == null)
throw new Exception("PART_ZoomCanvas template is missing!");
this.zoomSlider = Template.FindName("PART_ZoomSlider", this) as Slider;
if (this.zoomSlider == null)
throw new Exception("PART_ZoomSlider template is missing!");
this.designerCanvas.LayoutUpdated += new EventHandler(this.DesignerCanvas_LayoutUpdated);
this.zoomThumb.DragDelta += new DragDeltaEventHandler(this.Thumb_DragDelta);
this.zoomSlider.ValueChanged += new RoutedPropertyChangedEventHandler<double>(this.ZoomSlider_ValueChanged);
this.scaleTransform = new ScaleTransform();
this.designerCanvas.LayoutTransform = this.scaleTransform;
}
private void ZoomSlider_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
{
double scale = e.NewValue / e.OldValue;
double halfViewportHeight = this.ScrollViewer.ViewportHeight / 2;
double newVerticalOffset = ((this.ScrollViewer.VerticalOffset + halfViewportHeight) * scale - halfViewportHeight);
double halfViewportWidth = this.ScrollViewer.ViewportWidth / 2;
double newHorizontalOffset = ((this.ScrollViewer.HorizontalOffset + halfViewportWidth) * scale - halfViewportWidth);
this.scaleTransform.ScaleX *= scale;
this.scaleTransform.ScaleY *= scale;
this.ScrollViewer.ScrollToHorizontalOffset(newHorizontalOffset);
this.ScrollViewer.ScrollToVerticalOffset(newVerticalOffset);
}
private void Thumb_DragDelta(object sender, DragDeltaEventArgs e)
{
double scale, xOffset, yOffset;
this.InvalidateScale(out scale, out xOffset, out yOffset);
this.ScrollViewer.ScrollToHorizontalOffset(this.ScrollViewer.HorizontalOffset + e.HorizontalChange / scale);
this.ScrollViewer.ScrollToVerticalOffset(this.ScrollViewer.VerticalOffset + e.VerticalChange / scale);
}
private void DesignerCanvas_LayoutUpdated(object sender, EventArgs e)
{
double scale, xOffset, yOffset;
this.InvalidateScale(out scale, out xOffset, out yOffset);
this.zoomThumb.Width = this.ScrollViewer.ViewportWidth * scale;
this.zoomThumb.Height = this.ScrollViewer.ViewportHeight * scale;
Canvas.SetLeft(this.zoomThumb, xOffset + this.ScrollViewer.HorizontalOffset * scale);
Canvas.SetTop(this.zoomThumb, yOffset + this.ScrollViewer.VerticalOffset * scale);
}
private void InvalidateScale(out double scale, out double xOffset, out double yOffset)
{
// designer canvas size
double w = this.designerCanvas.ActualWidth * this.scaleTransform.ScaleX;
double h = this.designerCanvas.ActualHeight * this.scaleTransform.ScaleY;
// zoom canvas size
double x = this.zoomCanvas.ActualWidth;
double y = this.zoomCanvas.ActualHeight;
double scaleX = x / w;
double scaleY = y / h;
scale = (scaleX < scaleY) ? scaleX : scaleY;
xOffset = (x - scale * w) / 2;
yOffset = (y - scale * h) / 2;
}
}
}