x, y in struct _SynapticsSHM is ABS_X, ABS_Y, why not ABS_MT_POSITION_X, ABS_MT_POSITION_Y?

Wed Jan 15 01:43:31 PST 2014

Hi Peter,

I am debugging geis-2.2.16 these days, and also read about synaptics 
1.7.x source code, in 1.7.x, it uses xf86PostTouchEvent, post multitouch 
event to X, then the client application, such as touchegg, is able to 
get XEvent in a while loop, is that right?

But in 1.7.x src/eventcomm.c, about the 576 line, it still treats 
ABS_MT_POSITION_X as cumulative_dx, and I read about your libtouchpad 
source code hosting on github src/touchpad-events.c, about the 42 line, 
it correctly treats ABS_MT_POSITION_X as x.

Take Linux multitouch protocol type B for example,

ABS_MT_SLOT 0
ABS_MT_TRACKING_ID 45
ABS_MT_POSITION_X x[0]
ABS_MT_POSITION_Y y[0]
ABS_MT_SLOT 1
ABS_MT_TRACKING_ID 46
ABS_MT_POSITION_X x[1]
ABS_MT_POSITION_Y y[1]
SYN_REPORT

During a SYN_REPORT period, there are might several (ABS_MT_POSITION_X, 
ABS_MT_POSITION_Y) 2D points to indicate the positions where 
multi-fingers touched, but synaptics 1.7.x only maintain 1 
(ABS_MT_POSITION_X, ABS_MT_POSITION_Y) point, it might lost other 
multitouch points.
It is able to switch to tty2, because synaptics process used device file 
descriptor, run evtest /dev/input/eventX to print_absdata, and I have no 
idea how to directly read the device fd under tty7, such as gnome shell, 
kde, sort of DE... thanks a lot :)

> On Wed, Jan 08, 2014 at 09:28:29PM +0800, Zhai Xiang wrote:
>> Hi Peter,
>>
>> Sorry for my late reply because I wen to Beijing for a short business
>> travel.
>>
>> Yes, I read about the source code about 1.7.x by apt-get source
>> xserver-xorg-input-synaptics under Linux Deepin 2014, the SHM has been
>> completely removed.
> generally I recommend looking at the git sources before you hack on any
> software project, much more likely to be up-to-date than the package a
> distribution ships.
>
>> And I do not want to hack the 1.6.x source code under Linux Deepin 2013 to
>> support ABS_MT_SLOT, ABS_MT_POSITION_X && ABS_MT_POSITION_Y sort of
>> multitouch support, even it supports multitouch and gesture recognition,
>> such as 2 fingers to zoom out/in, 4 fingers swipe up to show all open
>> windows, 4 fingers swipe right to switch to 2nd work space, 4 fingers swipe
>> left to switch to 1st work space, 3 fingers to move active window, the demo
>> video shown as http://v.youku.com/v_show/id_XNjU5MTk4MTk2.html
>>
>> You said you are writing the driver with multitouch support using a
>> different base design, can I ask whether or not the driver`s source code
>> will be accepted by xorg official maintainer?
> well, given that I'm the input maintainer I'm gonna say "yes" :)
>
>> Would it be OK for you if I also contribute to your driver? If it is OK,
>> may I have your driver source code version control link such as github or
>> something else?
> it's called libinput but currently spread across some personal github
> repositories. it'll be on freedesktop soon, but it's still very early
> stages with a lot of the top-level work to be sorted out first so it's a bit
> too early to go full volume on hacking on it. I've got an experimental
> driver in https://github.com/whot/libtouchpad which is a test-bed for a
> couple of things that I'll move over to libinput eventually.
>
> Cheers,
>     Peter
>
>> 2014/1/6 Peter Hutterer <peter.hutterer at who-t.net>
>>
>>> On Sat, Jan 04, 2014 at 04:25:51PM +0800, Leslie Zhai wrote:
>>>> Hi xorg developers,
>>>>
>>>> in xserver-xorg-input-synaptics-1.6.2/include/synaptics.h
>>>> the struct _SynapticsSHM is shown as below:
>>> SHM has been completely removed in synaptics 1.7, it's largely a leftover
>>> from before device properties where it was needed for run-time
>>> configuration. it had't been updated in a while, so any code that deals
>>> with
>>> it is likely outdated.
>>>
>>> updating synaptics to support multitouch properly is a bit of a larger
>>> issue, it's likely easier to write the driver from scratch using a
>>> different
>>> base design (which I'm currently in the process of doing).
>>>
>>> Cheers,
>>>     Peter
>>>
>>>> ```
>>>> typedef struct _SynapticsSHM {
>>>> int version; /* Driver version */
>>>>
>>>> /* Current device state */
>>>> int x, y; /* actual x, y coordinates */
>>>> int z; /* pressure value */
>>>> int numFingers; /* number of fingers */
>>>> int fingerWidth; /* finger width value */
>>>> int left, right, up, down; /* left/right/up/down buttons */
>>>> Bool multi[8];
>>>> Bool middle;
>>>> } SynapticsSHM;
>>>> ```
>>>>
>>>> there are x and y, because I want to know what they are, then read about
>>>> src/eventcomm.c
>>>> ```
>>>> if (ev.code < ABS_MT_SLOT) {
>>>> switch (ev.code) {
>>>> case ABS_X:
>>>> hw->x = apply_st_scaling(proto_data, ev.value, 0);
>>>> break;
>>>> case ABS_Y:
>>>> hw->y = apply_st_scaling(proto_data, ev.value, 1);
>>>> break;
>>>> case ABS_PRESSURE:
>>>> hw->z = ev.value;
>>>> break;
>>>> case ABS_TOOL_WIDTH:
>>>> hw->fingerWidth = ev.value;
>>>> break;
>>>> }
>>>> }
>>>> ```
>>>>
>>>> Why use ABS_X for hw->x?
>>>> I want to recognize multi-touch gesture, such as zoom in/out, with
>>>> ABS_MT_SLOT, ABS_MT_POSITION_X and ABS_MT_POSITION_Y based on Linux
>>>> Multi-touch (MT) Protocol.
>>>> But struct _SynapticsSHM only provides ABS_X and ABS_Y, even there is
>>>> numFingers, it is still unable to distinguish which finger touching the
>>>> point1, point2 or pointN...
>>>>
>>>> So I hacked the struct _SynapticsSHM, added int slot, mt_x, mt_y, shown
>>>> as below:
>>>> ```
>>>> typedef struct _SynapticsSHM {
>>>> int version; /* Driver version */
>>>>
>>>> /* Current device state */
>>>> int x, y; /* actual x, y coordinates */
>>>> int z; /* pressure value */
>>>> int numFingers; /* number of fingers */
>>>> int fingerWidth; /* finger width value */
>>>> int left, right, up, down; /* left/right/up/down buttons */
>>>> Bool multi[8];
>>>> Bool middle;
>>>>
>>>> int slot;
>>>> int mt_x;
>>>> int mt_y;
>>>> } SynapticsSHM;
>>>> ```
>>>>
>>>> and also hacked src/eventcomm.c, using ABS_MT_POSITION_X for mt_x, shown
>>>> as below:
>>>> ```
>>>> case EV_ABS:
>>>> if (ev.code == ABS_MT_SLOT)
>>>> hw->slot = ev.value;
>>>> if (ev.code == ABS_MT_POSITION_X)
>>>> hw->mt_x = ev.value;
>>>> if (ev.code == ABS_MT_POSITION_Y)
>>>> hw->mt_y = ev.value;
>>>> ```
>>>>
>>>> Then I can use slot, mt_x, mt_y to recognize multi-touch gesture such as
>>>> zoom in, rotate ... but that is hacking way, perhaps there are some
>>>> synaptics developers already considered about multi-touch gesture
>>>> recognization requirement, it might be in TODO list.
>>>>
>>>> Please someone give me some advice, thanks a lot!
>>>>
>>>> Leslie Zhai
>>>> _______________________________________________
>>>> xorg-devel at lists.x.org: X.Org development
>>>> Archives: http://lists.x.org/archives/xorg-devel
>>>> Info: http://lists.x.org/mailman/listinfo/xorg-devel
>>>>

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