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Implementing a custom zoom using mouse events handlers


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I am trying to implement a custom zoom solution for ChartFX, and the code looks something like this:

private Point startPoint = Point.Empty;

// On mouse down, save the starting point
void chart_MouseDownEvent(object sender, _ChartEvents_MouseDownEvent e)
startPoint = new Point(e.args.X, e.args.Y);

// On mouse up, zoom to coordinates
void chart_MouseUpEvent(object sender, _ChartEvents_MouseUpEvent e)
if (e.args.Button != ButtonLeft)

// override regular functionality
e.args.Handled = true;

Point endPoint = new Point(e.args.X, e.args.Y);

Axis xAxis = chart.AxisX;
Axis yAxis = chart.AxisY;

double minX = xAxis.PixelToValue(startPoint.X);
double maxX = xAxis.PixelToValue(endPoint.X);

double minY = yAxis.PixelToValue(startPoint.Y);
double maxY = yAxis.PixelToValue(endPoint.Y);

if (!axChart1.Zoom)
axChart1.Zoom = true;

xAxis.Zoom(Math.Min(minX, maxX), Math.Max(minX, maxX));
yAxis.Zoom(Math.Min(minY, maxY), Math.Max(minY, maxY));

The problem is that, after I handle the event, zoom selection dashed rectangle remains visible (and active as I move the mouse). I bypassed the standard functionality (I did set the Handled property to true), but it seems like it still remains in this "in-the-middle-of-zoom" mode.

Does anyone have any experience with implementing custom zoom functionality? Maybe someone has encountered this before.

Thanks a lot!

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By setting:

e.args.Handled = true;

You are preventing everything that was going to be done on that event from executing. In this case this includes clearing the flag that says the selection rectangle is vissible.

In order to make this work, you also set the Handled property to true in the MouseDown event and handle the draing of the selection rectangle in your MouseMove/PostPaint event handlers.

Another option is that instead of zooming-in right away when you get the call to MouseUp, let the library take its course and perform the regular zoom, then by using a timer or a PostBack message thta gets fired on MouseUp, adjust it according to your needs.


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