I have a GXT chart displaying line curves for a given X and Y data range. Now I want to add a sprite to the chart to show at a specific point. I can add such a sprite using pixel coordinates but then it's in the wrong place with respect to the curves which have been rendered based on data coordinates. I cannot find a way to map pixel coordinates to data coordinates. I am trying to get axis bounding boxes but these are always zero, probably because they have not been fully rendered at the moment when I retrieve them.

Does anyone have a solution to this problem?