fAbsXlowNDC is nul in case of a single pad but is not in case of multiple pads (Divide()). So you should one method or the other depending if you want to convert in pixels in “Canvas pixel coordinates” or in the current “pad pixel coordinates”. I would suggest you create a canvas with multiple subpads and make yourself some tries to understand the difference.
[quote=“timtran”]Hi,
I am trying to understand better the coordinate systems used in ROOT, so that I can read and understand the implementations for zooming.
[/quote]Please check the TQtZoomPadWidget root.bnl.gov/QtRoot/htmldoc/TQtZ … escription