ZoomExtents method call works different than activating ZoomExtents through gesture

Question

I've been working on a small 3D preview window in a MVVM style application... The view is created then its data context is set. Therefore it seems that ZoomExtentsWhenLoaded="True" doesn't seem to help do what I need. I need something like, ZoomExtentsWhenDataContextChanges.

Interestingly, I've found that if I use a mouse gesture like the one defined below, I can physically click on the HelixViewport3D and it will perform a ZoomExtents.

HelixViewport3D.ZoomExtentsGesture = new MouseGesture(MouseAction.LeftDoubleClick);

However, if do something like this...

HelixViewport3D.DataContextChanged += (o, e) => ResetCamera();

private void ResetCamera()
{
    var dc = HelixViewport3D.DataContext as WellSurveyPlot3DViewModel;
    HelixViewport3D.ResetCamera();
    HelixViewport3D.Camera = dc.PerspectiveCamera;
    HelixViewport3D.ZoomExtents();
}

The viewport does zoom, it just doesn't center itself, like it does when activating ZoomExtents when using the mouse gesture.

I tried ResetCamera, and several other things... What is the standard way of dealing with keeping a viewport around and swapping out the DataContext instead of creating a new one each time?

score 1 · Accepted Answer · edited Jul 15 '20 at 02:15

I fixed this with an attached property. I read through the HelixViewport3D source code and got this idea, after noticing how the camera works. It seems an update to the default camera through a property binding doesn't really do anything after the control is initialized.

      public static class HelixViewport3DZoomExtent
    {
        private static readonly Type OwnerType = typeof(HelixViewport3DZoomExtent);
        public static readonly DependencyProperty ZoomExtentsOnUpdateProperty = DependencyProperty.RegisterAttached("ZoomExtentsOnUpdate", typeof(bool), OwnerType, new PropertyMetadata(false, OnDataContextChanged));

        public static bool GetZoomExtentsOnUpdate(DependencyObject obj)
        {
            return (bool)obj.GetValue(ZoomExtentsOnUpdateProperty);
        }
        public static void SetZoomExtentsOnUpdate(DependencyObject obj, bool value)
        {
            obj.SetValue(ZoomExtentsOnUpdateProperty, value);
        }
        private static void OnDataContextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var viewport = d as HelixViewport3D;
            if (viewport == null) return;
            if (viewport.DataContext == null) return;
            viewport.Camera = viewport.DefaultCamera;
            viewport.ZoomExtents();
        }
    }

Here is the Xaml

     <Border BorderBrush="Black" BorderThickness="1">

        <Grid>

            <h:HelixViewport3D Name="HelixViewport3D" 
                               PanGesture="LeftClick"
                               DataContext="{Binding PreviewPlot, UpdateSourceTrigger=PropertyChanged}"
                               DefaultCamera="{Binding PerspectiveCamera, UpdateSourceTrigger=PropertyChanged}" 
                               services:HelixViewport3DZoomExtent.ZoomExtentsOnUpdate="{Binding RelativeSource={RelativeSource AncestorType={x:Type views:WellSurveyPlot3DPreview}}, 
                                                                                        Path=DataContext.PreviewUpdatedReZoom, UpdateSourceTrigger=PropertyChanged}">

                <h:SunLight/>

                <h:TubeVisual3D  Path="{Binding TubePath}" Diameter="75" ThetaDiv="12" IsPathClosed="False" Fill="LightGray"/>

                <h:GridLinesVisual3D Width="{Binding GridLength}" Length="{Binding GridLength}" MajorDistance="{Binding MajorGridLines}" Thickness="25"
                                 MinorDistance="{Binding MajorGridLines, UpdateSourceTrigger=PropertyChanged}" LengthDirection="1,0,0" Normal="0,0,1" 
                                 Center="{Binding BottomPlaneCenter,UpdateSourceTrigger=PropertyChanged}" Fill="Red"   />
                <h:GridLinesVisual3D Width="{Binding GridLength}" Length="{Binding GridLength, UpdateSourceTrigger=PropertyChanged}" LengthDirection="0,0,1" Normal="1,0,0"  Thickness="25"
                                 MajorDistance="{Binding MajorGridLines}" MinorDistance="{Binding MajorGridLines}"
                                 Center="{Binding BackLeftPlaneCenter, UpdateSourceTrigger=PropertyChanged}" Fill="Blue" />
                <h:GridLinesVisual3D Width="{Binding GridLength}" Length="{Binding GridLength, UpdateSourceTrigger=PropertyChanged}" LengthDirection="1,0,0" Normal="0,1,0" Thickness="25"
                                 MajorDistance="{Binding MajorGridLines}" MinorDistance="{Binding MajorGridLines}" 
                                 Center="{Binding BackRightPlaneCenter,UpdateSourceTrigger=PropertyChanged}" Fill="Green" />

            </h:HelixViewport3D>

            <Button Content="Open Well Viewer" HorizontalAlignment="Left"  VerticalAlignment="Top" Command="{Binding OpenWindowCmd}"/>

        </Grid>
    </Border>

In my view model I have to toggle my PreviewUpdateReZoom property.

    private void LoadSurveyPoints(List<WellSurveyPointCalculated> surveyPoints)
        {
            _coordinatesCalculator = _calcGlobalCoordsFactory.Create(surveyPoints);
            _wellXyzCoordinates = _coordinatesCalculator.PlotGlobalCoordinates(100).ToList();
            PreviewPlot = WellSurveyPlot3DViewModel();
            PreviewUpdatedReZoom = false;//Toggle true false to send property changed and get attached property to fire.
            PreviewUpdatedReZoom = true;
        }

This now works such that every new item drawn into the viewport has the correct camera settings and zooms to extents...

ZoomExtents method call works different than activating ZoomExtents through gesture

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