Right now, scrolling a window does a jump-scroll, that *pretends* to be smooth and little by little. But it wants to jump something like 6 lines at a time, and not give me any finegrain control.
What I want fine-grain control for: When reading a story online, I adjust the size of the window so that the text of the story is as close to my eye's "intake size" as possible. I adjust so that the top of the text is where the top of the viewing region is, and the size of the window is such that page-down does not move that line on the next page (i.e. -- the pagedown leaves the next page's topline at the same pixel point as the previous page's topline).
This means that I want to put that line I want to start reading from right at the top of the reading zone.
Chrome lets me do this without any issue. I can move things single-pixel.
Firefox wants to jump-scroll, making it impossible to get the text aligned where I'm reading.