Hi !

I have multiple plot organized in a vertical layout, inside a scrollArea. Each plot is connected to the other so that when one is dragged, the other are too.

Now, I want to be able to draw a horizontal line over all the plot when I click on the mouse. I will the use the coordinate of the line to get the data that are on the same coordinate to compute the average.

The data computation shouldn't be too difficult. But I really can't find a way to draw this line (I also want to be able to delete it and make it appear elsewhere to compute another mean). Like, I just need a line that goes from the top to the bottom of all the plots...
Do you have any advice to achieve this ?

The next step would be to draw two line and the compute the average for each plot between the two lines, but just be able to draw one would be a good step for me ^^