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

[Peter Hutterer]

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it is likely outdated.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
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