Problem with touch gestures handling.

kiug

Hi everyone,

I have three different touch screens:

the official Raspberry Pi touch screen (https://www.raspberrypi.org/blog/the-eagerly-awaited-raspberry-pi-display/) ,
7 inch capacitive touch screen from Waveshare (http://www.waveshare.com/wiki/7inch_HDMI_LCD_(B))
and touch monitor Dell S2240T (http://www.dell.com/ed/business/p/dell-s2240t/pd) .

I would like to implement some touch gestures, but it looks like handling events with Qt (5.5.0) is different on different touch screens.
On the official Raspberry Pi touch screen mouse events doesn't come to the event handler method, but on the other touch screens mouse events appear. This causes the button doesn't respond to tap gestures.

I wrote simple application to demonstrate this problem.

touchscreen_test.pro

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = touchscreen_test
TEMPLATE = app


SOURCES += main.cpp\
        mainwindow.cpp

HEADERS  += mainwindow.h

FORMS    += mainwindow.ui

main.cpp

#include "mainwindow.h"
#include <QApplication>
#include <QFile>
#include <QTextStream>
#include <QDateTime>

void messageHandler(QtMsgType type, const QMessageLogContext &context, const QString &msg)
{
    Q_UNUSED(context);

    QString time = QDateTime::currentDateTime().toString("yyyy-MM-dd hh:mm:ss");
    QString txt = QString("[%1] ").arg(time);

    int t = type;
    switch (t)
    {
    case QtDebugMsg:
        txt += QString("{Debug} \t %1").arg(msg);
        break;
    case QtWarningMsg:
        txt += QString("{Warning} \t %1").arg(msg);
        break;
    case QtCriticalMsg:
        txt += QString("{Critical} \t %1").arg(msg);
        break;
    case QtFatalMsg:
        txt += QString("{Fatal} \t %1").arg(msg);
        abort();
        break;
    }

    QFile outFile("touchscreen_test.log");
    outFile.open(QIODevice::WriteOnly | QIODevice::Append);

    QTextStream textStream(&outFile);
    textStream << txt << endl;
}

int main(int argc, char *argv[])
{
    qInstallMessageHandler(messageHandler);
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void on_pushButton_clicked();

private:
    bool event(QEvent *);
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    setAttribute(Qt::WA_AcceptTouchEvents);
}

MainWindow::~MainWindow()
{
    delete ui;
}

bool MainWindow::event(QEvent *ev)
{
    int t = ev->type();
    if(t == QEvent::MouseButtonPress
            || t == QEvent::MouseButtonDblClick
            || t == QEvent::MouseButtonPress
            || t == QEvent::MouseButtonRelease
            || t == QEvent::TouchBegin
            || t == QEvent::TouchCancel
            || t == QEvent::TouchEnd
            || t == QEvent::TouchUpdate) {
        qDebug()<<ev->type();
    }
    if(t ==QEvent::TouchBegin)
    {
        ev->accept();
        return true;
    }
    else
        return QWidget::event(ev);
}

void MainWindow::on_pushButton_clicked()
{
    qDebug()<<"[MainWindow::on_pushButton_clicked] pushButton_clicked!";
}

mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>426</width>
    <height>397</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <widget class="QPushButton" name="pushButton">
      <property name="text">
       <string>PushButton</string>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
  <widget class="QStatusBar" name="statusBar"/>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources/>
 <connections/>
</ui>

The first touch screen (the official Raspberry Pi) gives this output:
...
[2016-06-17 13:44:55] {Debug} QEvent::Type(TouchBegin)
[2016-06-17 13:44:55] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:55] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:55] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:55] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:55] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:55] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:55] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:55] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:56] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchEnd)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchBegin)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchEnd)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchBegin)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:57] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:58] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:58] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:44:58] {Debug} QEvent::Type(TouchUpdate)
...

The second and third touch screen (Waveshare, Dell) gives this output:
...
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchBegin)
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:49] {Debug} QEvent::Type(MouseButtonPress)
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:49] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchEnd)
[2016-06-17 13:49:50] {Debug} QEvent::Type(MouseButtonRelease)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchBegin)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
[2016-06-17 13:49:50] {Debug} QEvent::Type(TouchUpdate)
...

Is there any way to enable mouse events for the official Raspberry Pi touch screen?

tushar

Hi Kiug,

I have tried your source code. I am having waveshare 10" screen with raspberry pi. Which runs a kiosk qt application. When I touch on screen it returns me the following logs. here is the link for product http://www.waveshare.com/wiki/10.1inch_HDMI_LCD

Mouse button pressed
Touch Update
Touch Update
Touch Update
Touch Update
Touch Update
Touch Update
Touch Update
Touch Update
Touch Update
Touch Update
Touch Update
Touch Update
Touch End
Mouse button release

It couldn't handling QPushbutton's any signal while touch. So, if you know anything related to this issue then kindly help me to come-out from it.

Thanks