What moment IRenderSurface returns true for IsSizeValidForDrawing?

I cannot figure out how to setup SciChartSurface so that it would be initialized right away and IsSizeValidForDrawing returned true.

Now I have the special case for the first call to the view with SciChartSurface and I start working with it after receiving SizeChanged event. In this event handler and afterwards IsSizeValidForDrawing gets true and later on all my requests to the view are OK. It’s quite inconvenient.

When does SciChartSurface get resized? What makes it resize?
Which moment does IsSizeValidForDrawing get true?
What should I do to make the size valid after instantiating or receiving first bunch of data ?
How can I make it progmammatically?

This is my xaml:
…

        <s:SciChartSurface.RenderableSeries>
            <s:FastLineRenderableSeries XAxisId="XAxis1" YAxisId="YAxis1" AntiAliasing="False" />
            <s:FastLineRenderableSeries XAxisId="XAxis2" YAxisId="YAxis2" AntiAliasing="False"  />
            <s:FastLineRenderableSeries XAxisId="XAxis1" YAxisId="YAxis1" AntiAliasing="False" />
            <s:FastLineRenderableSeries XAxisId="XAxis2" YAxisId="YAxis2" AntiAliasing="False" />
            <s:FastLineRenderableSeries XAxisId="XAxis1" YAxisId="YAxis1" AntiAliasing="False"/>
            <s:FastLineRenderableSeries XAxisId="XAxis2" YAxisId="YAxis2" AntiAliasing="False"/>
        </s:SciChartSurface.RenderableSeries>

        <s:SciChartSurface.XAxes>
            <s:NumericAxis Id="XAxis1" />
            <s:NumericAxis Id="XAxis2" />
        </s:SciChartSurface.XAxes>

        <s:SciChartSurface.YAxes>
            <s:NumericAxis Id="YAxis1"  />
            <s:NumericAxis Id="YAxis2" />
        </s:SciChartSurface.YAxes>
    </s:SciChartSurface>

    <Grid Grid.Row="1" x:Name="myOverviews">
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <s:SciChartOverview  Grid.Row="0" 
                    XAxisId="XAxis1"
                    ParentSurface="{Binding ElementName=mySurface}"
                    DataSeries="{Binding ElementName=mySurface, Path=RenderableSeries[4].DataSeries}"
                    SelectedRange="{Binding ElementName=mySurface, Path=XAxes[0].VisibleRange, Mode=TwoWay}"
                    Visibility ="Collapsed"
                    s:ThemeManager.Theme="BlackSteel">
        </s:SciChartOverview>

        <s:SciChartOverview Grid.Row="1" 
                    XAxisId="XAxis2"
                    ParentSurface="{Binding ElementName=mySurface}"
                    DataSeries="{Binding ElementName=mySurface, Path=RenderableSeries[4].DataSeries}"
                    SelectedRange="{Binding ElementName=mySurface, Path=XAxes[1].VisibleRange, Mode=TwoWay}"
                    Visibility ="Collapsed"
                    s:ThemeManager.Theme="BlackSteel">
        </s:SciChartOverview>
    </Grid>

All visibilities besides SciChartSurface are “Collapsed”

SciChart version 3.1.0.5077

Thank you