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Hi there
I have strange behavior with VerticalSliceModifier and ToolTipLabel.
Here we have line with x=88 and y=76.0
wring line Y value

Look at the data used as source for this series.
88 X value corresponds 11 index in the X values array, but there is other value under 11 index in the Y values array (77.3vs76):

X values
Y values

With using vs2015 Live Property Explorer you can see the current DataSeriesIndex = 10.

Actual current index

But if I zoom this chart the Y value becomes 77.3

After zoom value becomes OK

So what can I do with this problem?


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It’s actually very hard to solve this problem, as the Hit-test (the API which VerticalSlice relies on) is done on the mouse-coordinate which is limited by pixels.

e.g. say you have 100×100 pixels but 1000 data-points. Now at pixel X=10, Y=20 there can be several data-points. It is only when you zoom in that you find actually which data-point the vertical line annotation was over.

We have a similar ‘known issue’ on our board again related to the accuracy of hit-test (which is limited by mouse-pixels) but as yet don’t have a solution.

Do you agree with my analysis / have any comments about it?

Best regards,

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Yes, I understand, but unfortunately this is not admissible in our application because user has a possibility to move the line with keyboard arrows and figure on getting accurate value. What is the best workaround to avoid this issue?

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