I have a chart and I want the user to see the values when the pointer is on the points. By using digEmAll's help in the page finding the value of the points in a chart ,I could write the following code:
Point? prevPosition = null;
ToolTip tooltip = new ToolTip();
void chart1_MouseMove(object sender, MouseEventArgs e)
{
var pos = e.Location;
if (prevPosition.HasValue && pos == prevPosition.Value)
return;
tooltip.RemoveAll();
prevPosition = pos;
var results = chart1.HitTest(pos.X, pos.Y, false, ChartElementType.PlottingArea);
foreach (var result in results)
{
if (result.ChartElementType == ChartElementType.PlottingArea)
{
chart1.Series[0].ToolTip = "X=#VALX, Y=#VALY";
}
}
}
by the above code,the user can see the values when the pointer is near to a series.But now How can I let the user to see the values only when the pointer is on the points? I replaced
int k = result.PointIndex;
if (k >= 0)
{
chart1.Series[0].Points[k].ToolTip = "X=#VALX, Y=#VALY";
}
instead of
chart1.Series[0].ToolTip = "X=#VALX, Y=#VALY";
to solve my problem.But It wasn't usefull.
You should modify the code in this way:
Point? prevPosition = null;
ToolTip tooltip = new ToolTip();
void chart1_MouseMove(object sender, MouseEventArgs e)
{
var pos = e.Location;
if (prevPosition.HasValue && pos == prevPosition.Value)
return;
tooltip.RemoveAll();
prevPosition = pos;
var results = chart1.HitTest(pos.X, pos.Y, false,
ChartElementType.DataPoint);
foreach (var result in results)
{
if (result.ChartElementType == ChartElementType.DataPoint)
{
var prop = result.Object as DataPoint;
if (prop != null)
{
var pointXPixel = result.ChartArea.AxisX.ValueToPixelPosition(prop.XValue);
var pointYPixel = result.ChartArea.AxisY.ValueToPixelPosition(prop.YValues[0]);
// check if the cursor is really close to the point (2 pixels around the point)
if (Math.Abs(pos.X - pointXPixel) < 2 &&
Math.Abs(pos.Y - pointYPixel) < 2)
{
tooltip.Show("X=" + prop.XValue + ", Y=" + prop.YValues[0], this.chart1,
pos.X, pos.Y - 15);
}
}
}
}
}
The idea is to check if the mouse is very close to the point e.g. 2
pixels around it (because is really unlikely to be exactly on the point) and show the tooltip in that case.