Hi, On Fri, Nov 05, 2010 at 11:47:28AM -0700, Ping Cheng wrote: > Recent changes and discussion about MT support at LKML, UDS, and > xorg-devel encouraged me to migrate Wacom MT devices to the slot-based > MT protocol (introduced in kernel 2.6.36). Nice! > My goal is to understand how X server would like the MT data to be > reported from the kernel. I hope to keep kernel and X server driver MT > support in sync so we can avoid unnecessary confusion or extra work in > the userland. :) > The existing solution for single touch events is to arbitrate touch > when pen is in prox. This is based on the assumption that we do not > want to have two cursors competing on the screen. What do you mean by 'arbitrate' here? I guess you're talking about which events should send ABS_[XY]? > 1. Arbitrate all touch data in the kernel. > > This is the simplest solution for device driver developers. But I do > not feel it is end user and userland client friendly. > > [...] > > 3. Report first finger touch as ABS_X/Y events when pen is not in prox; > Report pen data as ABS_X/Y events when there is no finger touch; > Report touch data as MT_TOOL_TOUCH and pen data as MT_TOOL_PEN > events when both pen and touch data are received. No ABS_X/Y are > reported when pen and tocuh or multi-touch data are received. > > I feel this one makes sense to userland since pen can be considered as > another touch. I'd say that either #1 or #3 is the best idea here, simply because they seem to be the most straightforward, and thus easier to support. Assuming that xf86-input-wacom will track the state itself and decide (using whatever criteria) which events should send core x/y motion, then all you need to do with ABS_[XY] is just make a best effort to have it more or less work for dumb userspace clients. Cheers, Daniel
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