Programming pinch events on the Touch

[rkomar]

Does anyone know anything about handling pinch events within the Inkview API? The SDK hasn't been updated in a while, and there are new events showing up in the handler that aren't defined in inkview.h. Specifically event types 39 and 44 are showing up. EVT_TOUCHUP is 40, EVT_TOUCHDOWN is 41, and EVT_TOUCHMOVE is 42, so the new types are probably touch related, as well. I suspect that they are necessary to handle pinch events, but I have no idea how. Even source code for a program that handles pinches would be good. Is there no one writing applications for the Touch?

[DmitryZ]

Event 39 is EVT_MTSYNC, for multi-touch handling, par2 is touch count. Full information about the event is obtained with GetTouchInfo() function, it returns an array of iv_mtinfo structures. Here is an example:
iv_mtinfo *mti = GetTouchInfo();
int tcnt = par2;
int cx = (tcnt > 1) ? (mti[0].x + mti[1].x) / 2 : mti[0].x;
int cy = (tcnt > 1) ? (mti[0].y + mti[1].y) / 2 : mti[0].y;

Event 44 is EVT_POINTERDRAG, like EVT_POINTERMOVE but with some dead zone, to filter accidental finger move.

[rkomar]

Thanks! The 1.1a release of the SDK doesn't include the definition of iv_mtinfo. Does it look like this?:

typedef struct iv_mtinfo_s {
  int x;
  int y;
} iv_mtinfo;

or are short variables used instead of int, perhaps? Are there any other variables in the struct?

Also, will par2 (touch count) only ever be 1 or 2, or can there be more than that (for example, if three fingers are used)? I assume that the iv_mtinfo array only includes points from a single point in time, and not from multiple points concatenated together.

Finally, does par1 mean anything in EVT_MYSYNC events?

Oops, one more question: should the iv_mtinfo array returned by GetTouchInfo() be freed?

[rkomar]

There is no GetTouchInfo() function in libinkview.so within the 1.1a SDK. I guess this means that I cannot build an executable that handles multi-touch events until a new SDK comes out. Too bad. The function is also missing from libinkview.so on my 902 reader (2.1.3 firmware), so a different executable would have to be built for the Touch, or I'd have to figure out how to dynamically use the function.

Edit: I looks like I can build it using dlopen()/dlsym() to call the GetTouchInfo function if it exists. It's ugly code, though.

[DmitryZ]

Here is an actual inkview.h, with all needed structures and functions.
For 902, it's not a problem - you will call GetTouchInfo() only from MTSYNC event, there's no such event on 902, and because of lazy resolving, "unresolved symbol" will not occur.

[rkomar]

Thank you very much. The iv_mtinfo struct is quite different from what I imagined, so my guess would not have worked.

I cannot get the application to link if I call GetTouchInfo() because it is missing from my libinkview.so (SDK 1.1a). Anyways, it doesn't matter because I can use dlopen/dlsym to make the call inside the if(type == EVT_MTSYNC) {} block for now. I will have to wait for an updated SDK before I can write code to call the function directly.

[rkomar]

If anyone wants to know how to call GetTouchInfo() (or any other function) if it isn't part of their SDK, here's some simple example code showing how to do it:

#include <stdio.h>
#include <dlfcn.h>

#define EVT_MTSYNC 39
#define EVT_POINTERDRAG 44

typedef struct iv_mtinfo_s {
  int active;
  int x;
  int y;
  int pressure;
  int rsv_1;
  int rsv_2;
} iv_mtinfo;

iv_mtinfo* (*gti)(void);  /* Pointer to GetTouchInfo() function. */

int main_handler(int type, int par1, int par2) {
  void *handle;
  iv_mtinfo *mti;
  int i;

  if (type == EVT_INIT) {
    if ((handle = dlopen("libinkview.so", RTLD_LAZY))) {
      *(void **) (&gti) = dlsym(handle, "GetTouchInfo");
      dlclose(handle);
    } else
      gti = NULL;
  }
 
  if type == EVT_MTSYNC) {
    if (gti && (mti = (*gti)())) {
      for (i = 0; i < par2; i++)
        printf("   x = %d, y = %d\n", mti[i].x, mti[i].y);
    }
  }

  return 0;
}

Hopefully, this will go away when a new SDK comes out.