Qt 5.15 Multitouch issue

Hello everybody.
I have a strange issue that I don't understand and maybe you can help me.

Qt 5.15 compile with multiotuch support.

Code:

Qt Gui:
  Accessibility .......................... yes
  FreeType ............................... yes
    Using system FreeType ................ yes
  HarfBuzz ............................... no
    Using system HarfBuzz ................ no
  Fontconfig ............................. yes
  Image formats:
    GIF .................................. yes
    ICO .................................. yes
    JPEG ................................. yes
      Using system libjpeg ............... yes
    PNG .................................. yes
      Using system libpng ................ yes
  Text formats:
    HtmlParser ........................... yes
    CssParser ............................ yes
    OdfWriter ............................ yes
    MarkdownReader ....................... yes
      Using system libmd4c ............... no
    MarkdownWriter ....................... yes
  EGL .................................... yes
  OpenVG ................................. no
  OpenGL:
    Desktop OpenGL ....................... no
    OpenGL ES 2.0 ........................ yes
    OpenGL ES 3.0 ........................ yes
    OpenGL ES 3.1 ........................ yes
    OpenGL ES 3.2 ........................ yes
  Vulkan ................................. no
  Session Management ..................... yes
Features used by QPA backends:
  evdev .................................. yes
  libinput ............................... no
  INTEGRITY HID .......................... no
  mtdev .................................. yes
  tslib .................................. yes
  xkbcommon .............................. yes
  X11 specific:
    XLib ................................. yes
    XCB Xlib ............................. yes
    EGL on X11 ........................... no
    xkbcommon-x11 ........................ yes
QPA backends:
  DirectFB ............................... yes
  EGLFS .................................. yes
  EGLFS details:
    EGLFS OpenWFD ........................ no
    EGLFS i.Mx6 .......................... no
    EGLFS i.Mx6 Wayland .................. no
    EGLFS RCAR ........................... no
    EGLFS EGLDevice ...................... yes
    EGLFS GBM ............................ yes
    EGLFS VSP2 ........................... no
    EGLFS Mali ........................... no
    EGLFS Raspberry Pi ................... no
    EGLFS X11 ............................ no
  LinuxFB ................................ yes
  VNC .................................... yes
Qt Sql:
  SQL item models ........................ yes
Qt Widgets:
  GTK+ ................................... no
  Styles ................................. Fusion Windows
Qt PrintSupport:
  CUPS ................................... no
Qt Sql Drivers:
  DB2 (IBM) .............................. no
  InterBase .............................. no
  MySql .................................. yes
  OCI (Oracle) ........................... no
  ODBC ................................... no
  PostgreSQL ............................. no
  SQLite2 ................................ no
  SQLite ................................. no
    Using system provided SQLite ......... no
  TDS (Sybase) ........................... no
Qt Testlib:
  Tester for item models ................. yes

The examples in the widgets secction works fine. ( PinchZoom, FingerPaint and Knobs ).
But the issue is when I create a stupid app with 4 buttons and it's impossible to press two of them at the same time.
I enable the "qt.qpa.input" option to see what happen.

Code:

qt.qpa.input: udev device discovery for type QFlags<QDeviceDiscovery::QDeviceType>(Device_Touchpad|Device_Touchscreen)
qt.qpa.input: Found matching devices ("/dev/input/event6")
qt.qpa.input: evdevtouch: Adding device at /dev/input/event6
qt.qpa.input: evdevtouch: Using device /dev/input/event6
qt.qpa.input: Adding mouse at /dev/input/event6
qt.qpa.input: create mouse handler for "/dev/input/event6" ""
qt.qpa.input: evdevtouch: /dev/input/event6: Protocol type B (mtdev) (multi), filtered=no
qt.qpa.input: evdevtouch: /dev/input/event6: min X: 0 max X: 4095
qt.qpa.input: evdevtouch: /dev/input/event6: min Y: 0 max Y: 4095
qt.qpa.input: evdevtouch: /dev/input/event6: min pressure: 0 max pressure: 0
qt.qpa.input: evdevtouch: /dev/input/event6: device name: DATA MODUL easyMaxTouch

Qt recognize the device as Touch device and also it detects as MultiTouch Protocol type B.

Code:

# evtest /dev/input/event6 
Input driver version is 1.0.1
Input device ID: bus 0x3 vendor 0x7374 product 0x1252 version 0x111
Input device name: "DATA MODUL easyMaxTouch"
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    828
      Min        0
      Max     4095
      Resolution      20
    Event code 1 (ABS_Y)
      Value   1144
      Min        0
      Max     4095
      Resolution      26
    Event code 47 (ABS_MT_SLOT)
      Value      0
      Min        0
      Max       15
    Event code 53 (ABS_MT_POSITION_X)
      Value      0
      Min        0
      Max     4095
      Resolution      20
    Event code 54 (ABS_MT_POSITION_Y)
      Value      0
      Min        0
      Max     4095
      Resolution      26
    Event code 57 (ABS_MT_TRACKING_ID)
      Value      0
      Min        0
      Max    65535
Properties:
  Property type 1 (INPUT_PROP_DIRECT)
Testing ... (interrupt to exit)

So far, so good. But at this points, when I try to execute a stupid App with four buttons, just one can press.

What is missing or what is wrong ?
Thank you ver much in advance.

Re: Qt 5.15 Multitouch issue

I am pretty sure that the default higher-level behavior for QPushButton (and any class derived from QAbstractButton) is that only one button can be pressed at a time. If you want behavior that allows more than one "button" to be pressed simultaneously, then you will probably have to create your own widget to do this.

Even though multi-touch is enabled, by the time the event gets to a QAbstractButton, only one touch wins the race.

Re: Qt 5.15 Multitouch issue

Thank you very much for your response.

Maybe there is a mistake in my post. I have used QToolButton instead of QPusButton.
But anyway, QToolButton derives from QAbstractButton and surprisingly I have an application that I made years ago with several QToolButtons and 4 QDials and the multitouch works as expected.

I can press up to 10 QtoolButtons and I can operate 4 QDial with four fingers at the same time.
That's why I say I'm a bit confused, but thanks anyway and I'll try to figure out what I did.

Best regards

Re: Qt 5.15 Multitouch issue

Perhaps you have auto-repeat enabled for these buttons and dials. I can't find any property of QAbstractButton that you can set to allow multiple buttons to be active simultaneously.

It is possible that at a higher level, the handler for the buttons is responding to the QAbstractButton::pressed() signals sent by the separate buttons. As long as there have been no QAbstractButton::released() signals in between presses, this would simulate multiple simultaneous button presses.

If your program handles the QAbstractButton::clicked() or QAbstractButton::toggled() signals instead, those correspond to a pressed / released sequence, so it is impossible to detect multiple button presses.