MS Chart Control: prevent zoom when clicking

Question

I'm using a MS Chart Control that sets a cursor when the chart is clicked and that enables the user to zoom in and out. When the user tries to click into the chart it accidentally happens that he drags a very small zoom rectangle and the chart zooms in instead of handling the click.

What can be done to prevent zooming in when trying to click? Is there something like a minimum rectangle size for zooming?

Here's how I handle the click:

_area = new ChartArea();

private void chart1_MouseClick(object sender, MouseEventArgs e) 
{
    try 
    {
        _area.CursorX.SetCursorPixelPosition(new Point(e.X, e.Y), true);
    }
    catch (Exception ex) 
    { 

    }
}

And this is how I setup the zoom and cursor settings:

_area.AxisX.ScaleView.Zoomable = true;
_area.CursorX.IsUserSelectionEnabled = true;
_area.CursorX.IntervalType = DateTimeIntervalType.Seconds;
_area.CursorX.Interval = 1D;
_area.CursorY.IsUserSelectionEnabled = true;
_area.CursorY.Interval = 0;

@HansPassant Sorry, if I was not precise enough. I do not want to disable zooming. I just want to prevent an accidental zoom. — gus27, May 10 '18 at 14:54
Just provide a menu command or toolbar button to allow the user to reset the zoom. That way neither you nor us has to guess what an "accident" looks like. — Hans Passant, May 10 '18 at 15:00

Baddack · Answer 1 · 2018-05-10T15:05:21.197

1

You can manually handle zooming yourself. You can use the MouseDown event to capture the start X and start Y. Then use the MouseUp event to capture the end X and end Y. Once you have your start and end points you can determine if you want to zoom or not. If you want to zoom you can use the helper function below to manually zoom.

private void set_chart_zoom(ChartArea c, double xStart, double xEnd, double yStart, double yEnd)
{
    c.AxisX.ScaleView.Zoom(xStart, xEnd);
    c.AxisY.ScaleView.Zoom(yStart, yEnd);
}

edited May 10 '18 at 15:05

answered May 10 '18 at 14:59

Baddack

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Many thanks - that's definitely the key to handle the problem. – gus27 May 10 '18 at 15:51

gus27 · Accepted Answer · 2018-06-10T16:56:02.963

Based on @Baddack's answer here's a complete solution. The key is to disable the zoom feature of the chart and zoom manually (like Baddack suggested) by using MouseUp/MouseDown events. The user selection feature of the chart is kept enabled to use the selection rectangle for setting the zoom interval.

This sample code checks if the zoom retangle is at least 10 pixels wide and high. Only if that's the case the zoom is initiated:

private ChartArea _area;
private Point _chartMouseDownLocation;
...

private void MainForm_Load(object sender, EventArgs e)
{
    ...
    // Disable zooming by chart control because zoom is initiated by MouseUp event
    _area.AxisX.ScaleView.Zoomable = false;
    _area.AxisY.ScaleView.Zoomable = false;

    // Enable user selection to get the interval/rectangle of the selection for 
    // determining the interval for zooming
    _area.CursorX.IsUserSelectionEnabled = true;
    _area.CursorX.IntervalType = DateTimeIntervalType.Seconds;
    _area.CursorX.Interval = 1D;
    _area.CursorY.IsUserSelectionEnabled = true;
    _area.CursorY.Interval = 0;        
}

private void chart1_MouseDown(object sender, MouseEventArgs e)
{
    _chartMouseDownLocation = e.Location;
}

private void chart1_MouseUp(object sender, MouseEventArgs e)
{
    // Check if rectangle has at least 10 pixels with and hright
    if (Math.Abs(e.Location.X - _chartMouseDownLocation.X) > 10 && 
        Math.Abs(e.Location.Y - _chartMouseDownLocation.Y) > 10)
    {
        // Zoom to the Selection rectangle
        _area.AxisX.ScaleView.Zoom(
            Math.Min(_area.CursorX.SelectionStart, _area.CursorX.SelectionEnd),
            Math.Max(_area.CursorX.SelectionStart, _area.CursorX.SelectionEnd)
        );
        _area.AxisY.ScaleView.Zoom(
            Math.Min(_area.CursorY.SelectionStart, _area.CursorY.SelectionEnd),
            Math.Max(_area.CursorY.SelectionStart, _area.CursorY.SelectionEnd)
        );
    }
    // Reset/hide the selection rectangle
    _area.CursorX.SetSelectionPosition(0D, 0D);
    _area.CursorY.SetSelectionPosition(0D, 0D);
}

MS Chart Control: prevent zoom when clicking

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