WPF Datagrid zoom issue

Question

I'm working with the WPF DataGrid from the WPFToolkit and I'm having issues with trying to zoom the entire datagrid. My initial thought was that it was going to be really easy and I would just apply a scale transform to the grid and animate the ScaleX, ScaleY properties when the used clicked a button. This did not work however because the scrollbar was zoomed in making it larger. I need fixed headers and fixed columns on the datagrid so I can't simple use a scrollviewer outside of the datagrid to handle the scrolling. The second thing I tried was to just scale the font size in the grid, but this failed because on shrinking the font size the columns stay at the original width and do not shrink.

Finally I thought I had it working by using the below code which goes into the view tree for the datagrid and adds a scale transform to the Scroll Content Presenter. (Also not shown in this code, I apply a transform to the visual tree item for the headers in the same manner so that it scales as well). I thought this was working great until I tested out the horizontal scrolling after zooming. (Vertical scrolling works perfectly.) Before zooming at all the horizontal scrolling is fine, but after zooming, when I scroll horzonitally the display freaks out. It is hard to tell exactly what it is doing, but it sort of looks like the content that is scrolling off the left of the screen is "folding over" and coming back in on the left. Maybe it is just all smashing up on the left side. Does anyone have any ideas how I can get this working, hopefully without throwing out my whole datagrid that is already working quite well otherwise.

 ScrollContentPresenter sp = (ScrollContentPresenter)
VisualTreeHelper.GetChild(
VisualTreeHelper.GetChild(
VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(dgMatrix,     0), 0), 0),2);
ScaleTransform st = new ScaleTransform(1, 1);
sp.LayoutTransform = st;
DoubleAnimation a = new DoubleAnimation();
a.By = 1.5;
a.AutoReverse = false;
a.Duration = new Duration(TimeSpan.Parse("0:0:0.25"));
st.BeginAnimation(ScaleTransform.ScaleXProperty, a);
st.BeginAnimation(ScaleTransform.ScaleYProperty, a);

Answer 1

I figured out a solution. Don't know if this is the same way you did it or not:

<toolkit:DataGrid.CellStyle>
    <Style TargetType="{x:Type toolkit:DataGridCell}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type toolkit:DataGridCell}">
                    <ContentPresenter>
                        <ContentPresenter.LayoutTransform>
                            <ScaleTransform ScaleX="{Binding Path=Value, ElementName=ZoomFactor}"
                                            ScaleY="{Binding Path=Value, ElementName=ZoomFactor}" />
                         </ContentPresenter.LayoutTransform>
                     </ContentPresenter>
                 </ControlTemplate>
             </Setter.Value>
         </Setter>
     </Style>
 </toolkit:DataGrid.CellStyle>

Where ZoomFactor is a slider:

<Slider x:Name="ZoomFactor"
        Value="1"
        Minimum=".25"
        Maximum="5"
        Width="180" Margin="0,0,5,0"/>