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POWPF Custom FrameworkElement / IScrollInfo
 

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    <p>I've got a simple test app with a basic custom <code>FrameworkElement</code> implementation (TestElement below). The TestElement creates a couple of drawing visuals and draws some stuff in the constructor to a width of 600. It also implements the necessary bits of IScrollinfo; The Window containing the element has got a scrollviewer and a max size of 300x300. The scrollbar appears but does not scroll the content of the TestElement. </p> <p>Can anyone suggest whether what I am trying to do is possible and if so what I am doing wrong. I could re-render the drawing visuals in SetHorizontalOffset but don't want to for performance reasons as I have already drawn all I need to.</p> <p>I hope the question makes some sense - let me know if not and I can clarify.</p> <p>Many thanks - Karl</p> <pre><code>public class TestElement : FrameworkElement, IScrollInfo { DrawingVisual visual; DrawingVisual visual2; public TestElement() { Draw(); this.MaxWidth = 600; this.MaxHeight = 300; } public void Draw() { if(visual == null) { visual = new DrawingVisual(); base.AddVisualChild(visual); base.AddLogicalChild(visual); } if (visual2 == null) { visual2 = new DrawingVisual(); base.AddVisualChild(visual2); base.AddLogicalChild(visual2); } Random rand = new Random(); var pen = new Pen(Brushes.Black, 1); using(var dc = visual.RenderOpen()) { for (int i = 0; i &lt; 400; i++) { var r = rand.Next(10, 200); dc.DrawLine(pen, new Point(i, r), new Point(i, 0)); } } using (var dc = visual2.RenderOpen()) { for (int i = 0; i &lt; 200; i++) { var r = rand.Next(10, 200); dc.DrawLine(pen, new Point(i, r), new Point(i, 0)); } visual2.Offset = new Vector(400, 0); } } protected override int VisualChildrenCount { get { return 2; } } protected override Visual GetVisualChild(int index) { return index == 0 ? visual : visual2; } protected override Size MeasureOverride(Size availableSize) { viewport = availableSize; owner.InvalidateScrollInfo(); return base.MeasureOverride(availableSize); } protected override Size ArrangeOverride(Size finalSize) { var value = base.ArrangeOverride(finalSize); return base.ArrangeOverride(finalSize); } Point offset = new Point(0,0); public void SetHorizontalOffset(double offset) { this.offset.X = offset; this.InvalidateArrange(); } public void SetVerticalOffset(double offset) { this.offset.Y = offset; } public Rect MakeVisible(Visual visual, Rect rectangle) { throw new NotImplementedException(); } public bool CanVerticallyScroll { get; set; } public bool CanHorizontallyScroll { get; set; } Size extent = new Size(600, 300); private Size viewport = new Size(0, 0); public double ExtentWidth { get { return extent.Width; } } public double ExtentHeight { get {return extent.Height; } } public double ViewportWidth { get { return viewport.Width; } } public double ViewportHeight { get { return viewport.Height; } } public double HorizontalOffset { get { return offset.X; } } public double VerticalOffset { get { return offset.Y; } } private ScrollViewer owner; public ScrollViewer ScrollOwner { get { return owner; } set { owner = value; } } } </code></pre> <p>the xaml:</p> <pre><code>&lt;Window x:Class="TestWpfApp.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:l ="clr-namespace:TestWpfApp" Title="TestWpfApp" Height="300" Width="300" &gt; &lt;Grid&gt; &lt;ScrollViewer CanContentScroll="True" HorizontalScrollBarVisibility="Visible"&gt; &lt;l:TestElement CanHorizontallyScroll="True" /&gt; &lt;/ScrollViewer&gt; &lt;/Grid&gt; </code></pre> <p></p>
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