Display the exact measurement values for the size under the cursor

[lorentey]

I want to be able to easily access measurement values for any size.

• Make the chart interactive by automatically labeling curves with the measurement values corresponding to the horizontal position of the cursor.
• Allow me to select a particular size by e.g. option-clicking on the chart. This should toggle between the labels following the cursor and staying in place at the size I set.
• Allow me to switch between the labels displaying exact measurement values or speedup/slowdown factors relative to a particular task. For example, this could be toggled by option-clicking on a particular curve (or a line in the legend).