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ts_read_mt for 'single' touch devices #103

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craftyguy opened this Issue Sep 5, 2017 · 20 comments

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craftyguy commented Sep 5, 2017

This is a question, not an issue.

My project is using DirectFB, which uses tslib for handling touch input. The current code in DirectFB is calling ts_read(), however this means that MT devices are pretty much ignored. Would ts_read_mt generally serve as a replacement in this case to handle both MT devices (w/o EV_KEY) and 'single' touch devices (where EV_KEY is used)? The relevant code in DirectFB is only using the x, y, and pressure members of the ts_sample_mt. I didn't see much documentation to suggest that ts_read_mt does (or doesn't) return touch events for all touch devices or only MT devices.

Thanks!

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merge Sep 5, 2017

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both ts_read and ts_read_mt should read all touchscreen devices, MT or not. So this is a bug. Do you have this problem in a tslib release or the current git version only?

I quickly ran tests/ts_print and it works using a multitouch device. So what error messages do you get using ts_read() with a multitouch device.

(currently in git, we check whether we have EV_KEY, and only if we do, we fail for singletouch devices without BTN_TOUCH or BTN_LEFT.)

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merge commented Sep 5, 2017

both ts_read and ts_read_mt should read all touchscreen devices, MT or not. So this is a bug. Do you have this problem in a tslib release or the current git version only?

I quickly ran tests/ts_print and it works using a multitouch device. So what error messages do you get using ts_read() with a multitouch device.

(currently in git, we check whether we have EV_KEY, and only if we do, we fail for singletouch devices without BTN_TOUCH or BTN_LEFT.)

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also, the output of evtest would probably help.

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merge commented Sep 5, 2017

also, the output of evtest would probably help.

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Also, ts_print_mt works with such a singletouch device:


Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 330 (BTN_TOUCH)
  Event type 3 (EV_ABS)
    Event code 0 (ABS_X)
      Value   3236
      Min        0
      Max     4095
    Event code 1 (ABS_Y)
      Value   3455
      Min        0
      Max     4095
    Event code 24 (ABS_PRESSURE)
      Value      0
      Min        0
      Max      255

please specify your problem. thanks for reporting!

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merge commented Sep 5, 2017

Also, ts_print_mt works with such a singletouch device:


Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 330 (BTN_TOUCH)
  Event type 3 (EV_ABS)
    Event code 0 (ABS_X)
      Value   3236
      Min        0
      Max     4095
    Event code 1 (ABS_Y)
      Value   3455
      Min        0
      Max     4095
    Event code 24 (ABS_PRESSURE)
      Value      0
      Min        0
      Max      255

please specify your problem. thanks for reporting!

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craftyguy Sep 5, 2017

Thank you. I'm being a little cautious here because this is probably not a bug in tslib but a misunderstanding on my part of some components in tslib.

ts_test_mt seems to work perfectly find on this device I am looking at.

Just to give you some insight into what I am doing, I am writing a patch (which can be seen here) to update DirectFB (original source here) to support ts_read_mt instead of ts_read.

Is ts_sample.x the same as ts_sample_mt.x or should I be using ts_sample_mt.tool_x as a replacement?

craftyguy commented Sep 5, 2017

Thank you. I'm being a little cautious here because this is probably not a bug in tslib but a misunderstanding on my part of some components in tslib.

ts_test_mt seems to work perfectly find on this device I am looking at.

Just to give you some insight into what I am doing, I am writing a patch (which can be seen here) to update DirectFB (original source here) to support ts_read_mt instead of ts_read.

Is ts_sample.x the same as ts_sample_mt.x or should I be using ts_sample_mt.tool_x as a replacement?

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don't use tool_x. That's something different and not even used as of today. I don't even know a device that supports it.

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merge commented Sep 5, 2017

don't use tool_x. That's something different and not even used as of today. I don't even know a device that supports it.

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craftyguy Sep 5, 2017

I see. Thank you for the clarification. Something else is likely going on here, I will close this ticket now since I don't have any other questions about tslib! Thanks for making a great, useful library!

craftyguy commented Sep 5, 2017

I see. Thank you for the clarification. Something else is likely going on here, I will close this ticket now since I don't have any other questions about tslib! Thanks for making a great, useful library!

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make sure you allocate correctly, and only "once". We have a slightly unorthodox API here, with a pointer per " number of samples". See the example code and ask if not clear

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merge commented Sep 5, 2017

make sure you allocate correctly, and only "once". We have a slightly unorthodox API here, with a pointer per " number of samples". See the example code and ask if not clear

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I mean "nr of samples" pointers (like you have with the old ts_read() api, how many you to read non-blocking for example) each pointing to an array of real samples. those arrays are "slots" long.

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merge commented Sep 5, 2017

I mean "nr of samples" pointers (like you have with the old ts_read() api, how many you to read non-blocking for example) each pointing to an array of real samples. those arrays are "slots" long.

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craftyguy Sep 5, 2017

craftyguy commented Sep 5, 2017

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no. The fact that the ts_test_mt app works doesn't mean your app works. 2 different apps using tslib :) It seems like you're only allocating a pointer, but not the array of length 1 (1slot) that pointer should point at...

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merge commented Sep 5, 2017

no. The fact that the ts_test_mt app works doesn't mean your app works. 2 different apps using tslib :) It seems like you're only allocating a pointer, but not the array of length 1 (1slot) that pointer should point at...

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craftyguy commented Sep 5, 2017

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If it helps I'll write what I mean in a blindly written patch against directfb tomorrow.

malloc, like in ts_test_mt or ts_print_mt has to be done outside of your tslibEventThread().

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merge commented Sep 5, 2017

If it helps I'll write what I mean in a blindly written patch against directfb tomorrow.

malloc, like in ts_test_mt or ts_print_mt has to be done outside of your tslibEventThread().

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craftyguy commented Sep 5, 2017

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craftyguy Sep 5, 2017

both ts_read and ts_read_mt should read all touchscreen devices, MT or not. So this is a bug.

Somehow I read this earlier but it didn't quite register until @Pneumaticat pointed it out. Yes, this is a bug since ts_test doesn't work on his device but ts_test_mt does. He will be filing a separate bug for this and providing more info. Maybe a patch to DirectFB isn't necessary afterall!

craftyguy commented Sep 5, 2017

both ts_read and ts_read_mt should read all touchscreen devices, MT or not. So this is a bug.

Somehow I read this earlier but it didn't quite register until @Pneumaticat pointed it out. Yes, this is a bug since ts_test doesn't work on his device but ts_test_mt does. He will be filing a separate bug for this and providing more info. Maybe a patch to DirectFB isn't necessary afterall!

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Your patch to directfb is a good start. What you have to consider too though is that you have to optionally add ts_read_mt(). Basically #ifdef TSLIB_VERSION_MT. It still has to be able to be built against an old tslib with only ts_read(). At least if you think about patching directfb's main source upstream.

While having only 1 slot with ts_read_mt() is netter than ts_read, wouldn't directfb benefit from having multitouch, i.e. a fixed number of available slots, 5 or so? It would then at least be a possible followup patch.

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merge commented Sep 5, 2017

Your patch to directfb is a good start. What you have to consider too though is that you have to optionally add ts_read_mt(). Basically #ifdef TSLIB_VERSION_MT. It still has to be able to be built against an old tslib with only ts_read(). At least if you think about patching directfb's main source upstream.

While having only 1 slot with ts_read_mt() is netter than ts_read, wouldn't directfb benefit from having multitouch, i.e. a fixed number of available slots, 5 or so? It would then at least be a possible followup patch.

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Now I added a small change to ts_read() and it would be great if it could be tested if it works (for example with directfb).

I looked at directfb, but I don't know if it really would add value to have multitouch. I don't see other input driver that use multitouch or a way how to pass on multitouch data in directfb (no touch id in an input sample or something?). I might overlook something though.

It wouldn't be all that complicated. For the compiler, there is only one event thread (either ts_read of ts_read_mt) because you can do it with the preprocessor definition TSLIB_VERSION_MT. xf86-input-tslib does the same thing: https://github.com/merge/xf86-input-tslib/blob/master/src/tslib.c

And regarding slots at the tslib side of things: There is nothing you have to worry about. You allocate as many slots as you want, and pass the number to ts_read_mt() and the buffers will get filled up (a samples' "valid" variable gets 1 if you should care about it and 0 if have to ignore it). If it's a MT device, delivering multiple touch points currently, they just get valid in your allocated samples-array of length "slots". Just always read all slot's "valid" variable. If you allocate only 5 slots, and have a device capable of 10 slots, you simply limit the user to 5.

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merge commented Sep 6, 2017

Now I added a small change to ts_read() and it would be great if it could be tested if it works (for example with directfb).

I looked at directfb, but I don't know if it really would add value to have multitouch. I don't see other input driver that use multitouch or a way how to pass on multitouch data in directfb (no touch id in an input sample or something?). I might overlook something though.

It wouldn't be all that complicated. For the compiler, there is only one event thread (either ts_read of ts_read_mt) because you can do it with the preprocessor definition TSLIB_VERSION_MT. xf86-input-tslib does the same thing: https://github.com/merge/xf86-input-tslib/blob/master/src/tslib.c

And regarding slots at the tslib side of things: There is nothing you have to worry about. You allocate as many slots as you want, and pass the number to ts_read_mt() and the buffers will get filled up (a samples' "valid" variable gets 1 if you should care about it and 0 if have to ignore it). If it's a MT device, delivering multiple touch points currently, they just get valid in your allocated samples-array of length "slots". Just always read all slot's "valid" variable. If you allocate only 5 slots, and have a device capable of 10 slots, you simply limit the user to 5.

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Something like this might work. Its completely untested:

merge/DirectFB@011444b

but as I said. internally I haven't yet checked if DirectFB could make use of having real multitouch data. If yes, now it would be trivially easy to support it.

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merge commented Sep 6, 2017

Something like this might work. Its completely untested:

merge/DirectFB@011444b

but as I said. internally I haven't yet checked if DirectFB could make use of having real multitouch data. If yes, now it would be trivially easy to support it.

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but then again, please test the old ts_read() once again with your MT-only devices.

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merge commented Sep 6, 2017

but then again, please test the old ts_read() once again with your MT-only devices.

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craftyguy Sep 6, 2017

Yea that was my conclusion as well (about adding multitouch support to directfb). I (wrongly) thought that using ts_read_mt was necessary to support MT devices until #104.

Your patch is very helpful in demonstrating how to correctly handle old & new tslib versions, thank you for that!

I am preparing a package now with the latest commit in it so some users with MT-only devices can test with ts_read()

craftyguy commented Sep 6, 2017

Yea that was my conclusion as well (about adding multitouch support to directfb). I (wrongly) thought that using ts_read_mt was necessary to support MT devices until #104.

Your patch is very helpful in demonstrating how to correctly handle old & new tslib versions, thank you for that!

I am preparing a package now with the latest commit in it so some users with MT-only devices can test with ts_read()

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