MatrixTransform结合画布的宽度/高度 [英] MatrixTransform in combination with Width/Height of a Canvas

问题描述

在画布上放大图形时，我需要显示滚动条。

画布在ScrollViewer中，并且我增加了画布的宽度/高度，以便出现滚动条（

When zooming in on a drawing on a Canvas I have the requirement to show scrollbars.
The Canvas is in a ScrollViewer and I increase the Width/Height of the Canvas so that that the scollbars appear (otherwise they don't).

要放大1.1倍，请使用以下代码：

To zoom in with a factor of 1.1 I use this code:

Matrix m = this.LayoutTransform.Value;
if (e.Delta > 0) f = 1.1;
else f = 1.0 / 1.1;
m.Scale(f, f);
this.LayoutTransform = new MatrixTransform(m);
this.Height = this.ActualHeight * f;
this.Width = this.ActualWidth * f;

事实证明Canvas变得太大了。工程图放大10％，但宽度似乎变得像1.1的平方一样多20％。因此，我使用 Math.Sqrt（f）; 而不是 f 。

It turns out that the Canvas becomes much too large. The drawing zooms in 10% but the width seems to become 20% more like the square of 1.1. So I use Math.Sqrt(f); instead of f.

有人可以解释为什么这样做吗？

Can anybody explain why it behaves this way?

推荐答案

您应该只更改Canvas的LayoutTransform，例如在此简化示例中：

You should only change the LayoutTransform of the Canvas, like in this simplified example:

<ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
    <Canvas Width="1000" Height="1000" Background="Transparent"
            MouseWheel="Canvas_MouseWheel">
        <Canvas.LayoutTransform>
            <MatrixTransform/>
        </Canvas.LayoutTransform>
    </Canvas>
</ScrollViewer>

MouseWheel事件处理程序：

The MouseWheel event handler:

private void Canvas_MouseWheel(object sender, MouseWheelEventArgs e)
{
    var element = (FrameworkElement)sender;
    var transform = (MatrixTransform)element.LayoutTransform;
    var matrix = transform.Matrix;
    var scale = e.Delta >= 0d ? 1.1 : (1d / 1.1);

    matrix.Scale(scale, scale);
    transform.Matrix = matrix;

    e.Handled = true;
}

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