In javascript, I'm wanting to be able to highlight or point out certain points. I don't see a way to natively have custom highlight rules, so I thought maybe I could get the location of the points and draw something on the canvas. Problem with this is I don't know how to get coords of the points.
What would be the best way to accomplish this? Thanks.
You can click on the chart and add annotations at that point. That is discussed in Chapter 14 of the manual, Event Handling for Alarms and Tooltips. You can also enter a Note for a given sample interval, which will show in the table above the chart in the Notes row. See Chapter 10, around page 175, in the section Updating Chart Data.
The HTML Canvas used by the JavaScript library is internal to GWT code of the library and is not externally accessible for drawing. For the same reason, there is no way to access the actual pixel values of plotted objects in the Canvas.