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    SubjectRe: [PATCH] input: mt: Interface and MT_TOOL documentation updates
    On 12/10/2010 08:00 PM, Ping Cheng wrote:

    > On Fri, Dec 10, 2010 at 10:13 AM, Henrik Rydberg <> wrote:
    >>> Can we make MT_TOOL_ENVELOPE cover a bit more cases by:
    >>> 1. Removing ", and is only used for legacy hardware";
    >>> 2. Adding "Or the number of contacts inside the bounding rectangle is
    >>> reported if hardware provides the number but not the real contact
    >>> positions" to the end of the paragraph.
    >> You might disagree, but "old" is still somewhat apt in this situation.
    > It's ok if we say the new type was inspired by legacy hardware. But
    > saying that it "is only used for legacy hardware" closes the door for
    > future development. That's not what we are trying to do, right?

    Well, in a sense we are. I would agree that data aiming to provide gestures as a
    2D transformation matrix can be handled quite well with two tracked points and a
    finger count. However, a multitouch interface where users manipulate different
    objects on the screen simultaneously is a different story.

    >> How would you suggest we report the number of fingers?
    > I guess if we want to make it generic, we could have something like
    > ABS_MT_NUM_CONTACTS to go with MT_TOOL_ENVELOPE. Clients, such as
    > synaptics touchpads, that only care about the number of contacts
    > inside the envelope don't need to process the contact positions even
    > when they are reported. This also resolve the potential that
    > BTN_TOOL_QUADTAP is not enough to tell us how many contacts are on the
    > surface.

    I really would like to avoid adding a new way to solve an old problem, in
    particular given the statement above. Adding something like BTN_TOOL_QUINTAP
    would hurt a little bit, but not nearly as much.

    > Maybe we should also tell the clients whether they are going to get
    > the contact positions or not.

    I may not understand what you mean here, but if you are referring to an up-front
    declaration of what MT_TOOL types are to be expected, we did discuss this
    before, without any conclusion. Perhaps it is relevant to outline why this would
    be important.


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