Pyqtgraph still uses Qt's inaccuarate transform inversions in some places #1537
Description
As last evident in #1493, pyqtgraph cares greatly about inverse transform accuracy. But they are still places within it where Qt's transforms are used, like in ViewBox.updateScaleBox: there, pyqtgraph calls mapRectFromParent, which goes directly to Qt. In effect, updateScaleBox does not work properly if axes are zoomed a lot (to 1e15 and more) or data is very spread.
In Orange, we worked around that with biolab/orange3#3571, but our solution is neither pretty nor general. I am writing this as a note because I do not know pyqtgraph well enough to make a general pull request.
In pyqtgraph's code there are at least 6 more places where mapRectFromParent is used and they might be similarly problematic. Also, I would guess there are probably other Qt method calls in pyqtgraph that avoid pyqtgraph's accurate transforms.