On Wed, 13 Mar 2019 at 00:41:12 +0100, Ulf Brosziewski wrote: > The standard method of scrolling in X is tailored to mouse wheels and > proceeds in coarse steps. Wheel events are mapped to button events, and on > receiving such an event, an application moves the view of its data by some > fixed distance - usually the height of a line of text, or of a couple of > lines. > > Version 2.1 of the X Input Protocol has introduced a more precise > alternative. It defines additional types of motion events. In essence, > their values represent fractions of a complete scroll unit, and newer > applications may move their views by distances that are proportional to the > event values. For applications that don't support this, X generates the > standard button events whenever the values add up to the complete unit. > > synaptics(4) supports the newer method since long. > > The diffs below add the feature to ws and wstpad. The kernel part defines > two new event types in wsconsio.h, and it adapts the scrolling functions of > the touchpad input driver. The xenocara part adds the new "axes" and event > handlers to ws. > > There is a little twist to the implementation. While synaptics(4) > initializes the scroll axes with the scroll distance in device units, the > constant 4096 is used in the new ws code, and event values represent the > fraction (motion_delta / scroll_unit) in [*.12] fixed-point format. That > way, no queries for the device- and configuration-dependent scroll unit > are necessary. > > The X Input Protocol calls the method "smooth scrolling", but it seems > that nowadays, this term is used exclusively for the rendering technique > that displays a little animation when the document position changes, so > "precision scrolling" might be a better choice. > > Tests, comments, and OKs would be welcome.
Well done! It works on my touchpad and retains the old "chunky" style scrolling from the mouse wheel on my external mouse. My only quibble is that this new style scrolling seems much too fast by default with the default X and wscons mouse acceleration settings.
