wpf ScrollViewer and SizeChanged event

Question

Can anyone explain to me the relationship between ScrollViewer and SizeChanged event? Whenever I put a scrollViewer around a grid, numerous SizeChanged event gets fired. What is the relationship between the two? Thanks a lot.

EDIT:

From mdm20's comment, I noticed that the ActualWidth and ActualHeight of the grid increases continuously if I wrap the grid around a ScrollViewer. Can anyone explain why this is the case? Do I need to have hard values for the width and height of the grid?

EDIT #2:

The resizing is done through code posted below. Thanks for looking into this

    private void chartGrid_SizeChanged(object sender, SizeChangedEventArgs e)
    {
        textCanvas.Width = chartGrid.ActualWidth;
        textCanvas.Height = chartGrid.ActualHeight;
        legendCanvas.Children.Clear();
        chartCanvas.Children.RemoveRange(1, chartCanvas.Children.Count - 1);
        textCanvas.Children.RemoveRange(1, textCanvas.Children.Count - 1);
        AddChart();
    }

Corresponding XAML code is below:

<ScrollViewer Name="chartScrollViewer">
        <Grid Margin="0" x:Name ="chartGrid" Grid.Column="1" Grid.Row="1" ClipToBounds="True" Background="Transparent" SizeChanged="chartGrid_SizeChanged">
            <Canvas Margin="2" Name="textCanvas" ClipToBounds="True" Grid.Column="1" Grid.Row="1" Height="1200">
                <Canvas Name="chartCanvas" ClipToBounds="True">
                    <Canvas Name="legendCanvas" Background="Transparent" />
                </Canvas>
            </Canvas>
        </Grid>
</ScrollViewer>

Are they getting fired just when the window is loaded or constantly? — Mark, Oct 15 '10 at 20:23
Its when Window is loaded. I can't get pass window loading because of the constant calls — thomas1234, Oct 15 '10 at 20:30
What's inside the grid? Are you changing the size of anything in the sizechanged event creating a loop? — mdm20, Oct 15 '10 at 20:40
inside the grid is a canvas. I am changing the size of the canvas to the width and height of the grid container. But I don't see why this is called more than once during startup. — thomas1234, Oct 15 '10 at 20:43
Can you post the XAML and the code that changes the canvas size? — mdm20, Oct 15 '10 at 20:59

score 1 · Accepted Answer · edited Jun 14 '13 at 23:35

1

You are getting into a loop. I think what is happening is that when you change the canvas size, it prompts the grid to do a layout pass, which causes the ScrollViewer to do a layout pass, which causes the grid to resize itself, which starts the cycle over again.

edited Jun 14 '13 at 23:35

Dave Clemmer

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answered Oct 15 '10 at 21:47

mdm20

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wpf ScrollViewer and SizeChanged event

1 Answers1