add snap tooltip to cursor to see plot values

[trns1997]

Not sure if Issue #12 wanted this?

[leducp]

I expected a dedicated side panel but this one is still cool!

[trns1997]

ping @leducp

[leducp]

avoid get_ (Qt style)

[leducp]

snake case

[leducp]

This code can only works on the downsampled data or small series (< 300k). With a bigger serie, when zooming, the display will switch to the sections to display the full dataset but only on the current span (Level Of Detail approach).

A better approach could be to ask the series to do the rendering localy (like the curve plot): the plot create the tooltip, show mouse x, and each serie draw the nearest point x,y with scatter and color.
With such approach, the serie can switch between downsampled and sections and internal data do not need to be exposed
WDYT?

[trns1997]

This code can only works on the downsampled data or small series (< 300k). With a bigger serie, when zooming, the display will switch to the sections to display the full dataset but only on the current span (Level Of Detail approach).

A better approach could be to ask the series to do the rendering localy (like the curve plot): the plot create the tooltip, show mouse x, and each serie draw the nearest point x,y with scatter and color. With such approach, the serie can switch between downsampled and sections and internal data do not need to be exposed WDYT?

ah right clearly didnt try zooming in :/. Alright i will take you up on the approach