总体逻辑，修改发现设备和添加设备；
1、发现设备（qt-everywhere-src-5.15.6\qtbase\src\platformsupport\devicediscovery/qdevicediscovery_static.cpp）
需要修改的逻辑是，当/dev/input/路径下发生了文件的改动，需要重新加载设备列表，然后将设备重新添加使用；
1.1、头文件中（qdevicediscovery_static_p.h）
修改内容为：
添加设备名称列表（m_devices）；检测热插拔类（m_fileWatcher）；检测到文件变动后的槽函数（handleHotPlugWatch）；
1.2、修改源文件（qdevicediscovery_static.cpp）
修改内容：
构造函数中初始化热插拔监听，关联信号和槽；在浏览设备文件函数中（scanConnectedDevices），将可连接设备添加到设备列表中；槽函数中，判断文件路径是否在/devinput/下，然后再发送信号（deviceRemoved）断开设备，其次是调用浏览设备文件函数（scanConnectedDevices），获取可连接设备列表，最后是将设备文件名称用信号（deviceDetected）发送过去，用于连接；
2、添加设备（qt-everywhere-src-5.15.6\qtbase\src\platformsupport\input\evdevmouse）
该目录下主要是鼠标设备管理（qevdevmousemanager）和鼠标事件处理（qevdevmousehandler）
在设备管理文件中，可以看到调用发现设备类（qdevicediscovery），关联删除设备和添加设备；
在鼠标事件处理文件（qevdevmousehandler）中，主要是在函数（readMouseData），当连接失败后，需要做重连操作；
注：触摸屏可以做相同修改，但需要保存设备文件名称，以便再次打开；
3、源码附录
3.1、qdevicediscovery_static_p.h源码：
#ifndef QDEVICEDISCOVERY_STATIC_H
#define QDEVICEDISCOVERY_STATIC_H
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
#include "qdevicediscovery_p.h"
#include
#include
QT_BEGIN_NAMESPACE
class QDeviceDiscoveryStatic : public QDeviceDiscovery
{
Q_OBJECT
public:
QDeviceDiscoveryStatic(QDeviceTypes types, QObject *parent = 0);
QStringList scanConnectedDevices() Q_DECL_OVERRIDE;
private slots:
//重新更换设备文件，删除原有设备文件，发送新设备文件名称
void handleHotPlugWatch(const QString &path);
private:
bool checkDeviceType(const QString &device);
// 用于检测鼠标键盘热插拔
QFileSystemWatcher *m_fileWatcher;
// 原有的设备列表
QStringList m_devices;
};
QT_END_NAMESPACE
#endif // QDEVICEDISCOVERY_STATIC_H
3.2、qdevicediscovery_static.cpp源码：
#include "qdevicediscovery_static_p.h"
#include
#include
#include
#include
#include
#include
#include
#include
#include
/* android (and perhaps some other linux-derived stuff) don't define everything
* in linux/input.h, so we'll need to do that ourselves.
*/
#ifndef KEY_CNT
#define KEY_CNT (KEY_MAX+1)
#endif
#ifndef REL_CNT
#define REL_CNT (REL_MAX+1)
#endif
#ifndef ABS_CNT
#define ABS_CNT (ABS_MAX+1)
#endif
#ifndef ABS_MT_POSITION_X
#define ABS_MT_POSITION_X 0x35
#endif
#ifndef ABS_MT_POSITION_Y
#define ABS_MT_POSITION_Y 0x36
#endif
#define LONG_BITS (sizeof(long) * 8 )
#define LONG_FIELD_SIZE(bits) ((bits / LONG_BITS) + 1)
static bool testBit(long bit, const long *field)
{
return (field[bit / LONG_BITS] >> bit % LONG_BITS) & 1;
}
QT_BEGIN_NAMESPACE
Q_LOGGING_CATEGORY(lcDD, "qt.qpa.input")
QDeviceDiscovery *QDeviceDiscovery::create(QDeviceTypes types, QObject *parent)
{
return new QDeviceDiscoveryStatic(types, parent);
}
QDeviceDiscoveryStatic::QDeviceDiscoveryStatic(QDeviceTypes types, QObject *parent)
: QDeviceDiscovery(types, parent)
{
// 初始化文件监听器
m_fileWatcher = new QFileSystemWatcher(this);
m_fileWatcher->addPath(QString::fromLatin1(QT_EVDEV_DEVICE_PATH));// "dev/input/"
connect(m_fileWatcher, &QFileSystemWatcher::directoryChanged, this, &QDeviceDiscoveryStatic::handleHotPlugWatch);
qCDebug(lcDD) << "static device discovery for type" << types;
}
QStringList QDeviceDiscoveryStatic::scanConnectedDevices()
{
m_devices.clear();
QDir dir;
dir.setFilter(QDir::System);
// check for input devices
if (m_types & Device_InputMask) {
dir.setPath(QString::fromLatin1(QT_EVDEV_DEVICE_PATH));
foreach (const QString &deviceFile, dir.entryList()) {
QString absoluteFilePath = dir.absolutePath() + QLatin1Char('/') + deviceFile;
if (checkDeviceType(absoluteFilePath))
{
m_devices << absoluteFilePath;
}
}
}
// check for drm devices
if (m_types & Device_VideoMask) {
dir.setPath(QString::fromLatin1(QT_DRM_DEVICE_PATH));
foreach (const QString &deviceFile, dir.entryList()) {
QString absoluteFilePath = dir.absolutePath() + QLatin1Char('/') + deviceFile;
if (checkDeviceType(absoluteFilePath))
m_devices << absoluteFilePath;
}
}
qCDebug(lcDD) << "Found matching devices" << m_devices;
return m_devices;
}
bool QDeviceDiscoveryStatic::checkDeviceType(const QString &device)
{
int fd = QT_OPEN(device.toLocal8Bit().constData(), O_RDONLY | O_NDELAY, 0);
if (Q_UNLIKELY(fd == -1)) {
qWarning() << "Device discovery cannot open device" << device;
return false;
}
qCDebug(lcDD) << "doing static device discovery for " << device;
if ((m_types & Device_DRM) && device.contains(QString::fromLatin1(QT_DRM_DEVICE_PREFIX))) {
QT_CLOSE(fd);
return true;
}
long bitsAbs[LONG_FIELD_SIZE(ABS_CNT)];
long bitsKey[LONG_FIELD_SIZE(KEY_CNT)];
long bitsRel[LONG_FIELD_SIZE(REL_CNT)];
memset(bitsAbs, 0, sizeof(bitsAbs));
memset(bitsKey, 0, sizeof(bitsKey));
memset(bitsRel, 0, sizeof(bitsRel));
ioctl(fd, EVIOCGBIT(EV_ABS, sizeof(bitsAbs)), bitsAbs);
ioctl(fd, EVIOCGBIT(EV_KEY, sizeof(bitsKey)), bitsKey);
ioctl(fd, EVIOCGBIT(EV_REL, sizeof(bitsRel)), bitsRel);
QT_CLOSE(fd);
if ((m_types & Device_Keyboard)) {
if (testBit(KEY_Q, bitsKey)) {
qCDebug(lcDD) << "Found keyboard at" << device;
return true;
}
}
if ((m_types & Device_Mouse)) {
if (testBit(REL_X, bitsRel) && testBit(REL_Y, bitsRel) && testBit(BTN_MOUSE, bitsKey)) {
qCDebug(lcDD) << "Found mouse at" << device;
return true;
}
}
if ((m_types & (Device_Touchpad | Device_Touchscreen))) {
if (testBit(ABS_X, bitsAbs) && testBit(ABS_Y, bitsAbs)) {
if ((m_types & Device_Touchpad) && testBit(BTN_TOOL_FINGER, bitsKey)) {
qCDebug(lcDD) << "Found touchpad at" << device;
return true;
} else if ((m_types & Device_Touchscreen) && testBit(BTN_TOUCH, bitsKey)) {
qCDebug(lcDD) << "Found touchscreen at" << device;
return true;
} else if ((m_types & Device_Tablet) && (testBit(BTN_STYLUS, bitsKey) || testBit(BTN_TOOL_PEN, bitsKey))) {
qCDebug(lcDD) << "Found tablet at" << device;
return true;
}
} else if (testBit(ABS_MT_POSITION_X, bitsAbs) &&
testBit(ABS_MT_POSITION_Y, bitsAbs)) {
qCDebug(lcDD) << "Found new-style touchscreen at" << device;
return true;
}
}
if ((m_types & Device_Joystick)) {
if (testBit(BTN_A, bitsKey) || testBit(BTN_TRIGGER, bitsKey) || testBit(ABS_RX, bitsAbs)) {
qCDebug(lcDD) << "Found joystick/gamepad at" << device;
return true;
}
}
return false;
}
void QDeviceDiscoveryStatic::handleHotPlugWatch(const QString &path)
{
if(path.compare(QString::fromLatin1(QT_EVDEV_DEVICE_PATH)))
{
return;
}
QStringList devices;
// 先移除原来的设备
foreach (const QString &device, m_devices)
emit deviceRemoved(device);
// 获取现在的设备
// 注，这里获取的设备已经经过过滤，原因是在对该类进行实例化的时候
// 已经传进了筛选参数，如：QDeviceDiscovery::Device_Keyboard
devices = this->scanConnectedDevices();
// 重新添加设备
foreach (const QString &device, devices)
emit deviceDetected(device);
}
QT_END_NAMESPACE
3.3、qevdevmousehandler.cpp源码：
#include "qevdevmousehandler_p.h"
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#ifdef Q_OS_FREEBSD
#include
#else
#include
#include
#endif
#define TEST_BIT(array, bit) (array[bit/8] & (1<<(bit%8)))
QT_BEGIN_NAMESPACE
Q_LOGGING_CATEGORY(qLcEvdevMouse, "qt.qpa.input")
std::unique_ptr
{
qCDebug(qLcEvdevMouse) << "create mouse handler for" << device << specification;
bool compression = true;
int jitterLimit = 0;
int grab = 0;
bool abs = false;
const auto args = specification.splitRef(QLatin1Char(':'));
for (const QStringRef &arg : args) {
if (arg == QLatin1String("nocompress"))
compression = false;
else if (arg.startsWith(QLatin1String("dejitter=")))
jitterLimit = arg.mid(9).toInt();
else if (arg.startsWith(QLatin1String("grab=")))
grab = arg.mid(5).toInt();
else if (arg == QLatin1String("abs"))
abs = true;
}
int fd;
fd = qt_safe_open(device.toLocal8Bit().constData(), O_RDONLY | O_NDELAY, 0);
if (fd >= 0) {
::ioctl(fd, EVIOCGRAB, grab);
return std::unique_ptr
} else {
qErrnoWarning(errno, "Cannot open mouse input device %s", qPrintable(device));
return nullptr;
}
}
QEvdevMouseHandler::QEvdevMouseHandler(const QString &device, int fd, bool abs, bool compression, int jitterLimit)
: m_device(device), m_fd(fd), m_abs(abs), m_compression(compression)
{
setObjectName(QLatin1String("Evdev Mouse Handler"));
m_jitterLimitSquared = jitterLimit * jitterLimit;
// Some touch screens present as mice with absolute coordinates.
// These can not be differentiated from touchpads, so supplying abs to QT_QPA_EVDEV_MOUSE_PARAMETERS
// will force qevdevmousehandler to treat the coordinates as absolute, scaled to the hardware maximums.
// Turning this on will not affect mice as these do not report in absolute coordinates
// but will make touchpads act like touch screens
if (m_abs)
m_abs = getHardwareMaximum();
detectHiResWheelSupport();
// socket notifier for events on the mouse device
m_notify = new QSocketNotifier(m_fd, QSocketNotifier::Read, this);
connect(m_notify, &QSocketNotifier::activated,
this, &QEvdevMouseHandler::readMouseData);
}
QEvdevMouseHandler::~QEvdevMouseHandler()
{
if (m_fd >= 0)
qt_safe_close(m_fd);
}
void QEvdevMouseHandler::detectHiResWheelSupport()
{
#if defined(REL_WHEEL_HI_RES) || defined(REL_HWHEEL_HI_RES)
// Check if we can expect hires events as we will get both
// legacy and hires event and needs to know if we should
// ignore the legacy events.
unsigned char relFeatures[(REL_MAX / 8) + 1]{};
if (ioctl(m_fd, EVIOCGBIT(EV_REL, sizeof (relFeatures)), relFeatures) == -1)
return;
#if defined(REL_WHEEL_HI_RES)
m_hiResWheel = TEST_BIT(relFeatures, REL_WHEEL_HI_RES);
#endif
#if defined(REL_HWHEEL_HI_RES)
m_hiResHWheel = TEST_BIT(relFeatures, REL_HWHEEL_HI_RES);
#endif
#endif
}
// Ask touch screen hardware for information on coordinate maximums
// If any ioctls fail, revert to non abs mode
bool QEvdevMouseHandler::getHardwareMaximum()
{
unsigned char absFeatures[(ABS_MAX / 8) + 1];
memset(absFeatures, '\0', sizeof (absFeatures));
// test if ABS_X, ABS_Y are available
if (ioctl(m_fd, EVIOCGBIT(EV_ABS, sizeof (absFeatures)), absFeatures) == -1)
return false;
if ((!TEST_BIT(absFeatures, ABS_X)) || (!TEST_BIT(absFeatures, ABS_Y)))
return false;
// ask hardware for minimum and maximum values
struct input_absinfo absInfo;
if (ioctl(m_fd, EVIOCGABS(ABS_X), &absInfo) == -1)
return false;
m_hardwareWidth = absInfo.maximum - absInfo.minimum;
if (ioctl(m_fd, EVIOCGABS(ABS_Y), &absInfo) == -1)
return false;
m_hardwareHeight = absInfo.maximum - absInfo.minimum;
QScreen *primaryScreen = QGuiApplication::primaryScreen();
QRect g = QHighDpi::toNativePixels(primaryScreen->virtualGeometry(), primaryScreen);
m_hardwareScalerX = static_cast
m_hardwareScalerY = static_cast
qCDebug(qLcEvdevMouse) << "Absolute pointing device"
<< "hardware max x" << m_hardwareWidth
<< "hardware max y" << m_hardwareHeight
<< "hardware scalers x" << m_hardwareScalerX << 'y' << m_hardwareScalerY;
return true;
}
void QEvdevMouseHandler::sendMouseEvent()
{
int x;
int y;
if (!m_abs) {
x = m_x - m_prevx;
y = m_y - m_prevy;
}
else {
x = m_x / m_hardwareScalerX;
y = m_y / m_hardwareScalerY;
}
if (m_prevInvalid) {
x = y = 0;
m_prevInvalid = false;
}
emit handleMouseEvent(x, y, m_abs, m_buttons, m_button, m_eventType);
m_prevx = m_x;
m_prevy = m_y;
}
void QEvdevMouseHandler::readMouseData()
{
struct ::input_event buffer[32];
int n = 0;
bool posChanged = false, btnChanged = false;
bool pendingMouseEvent = false;
int eventCompressCount = 0;
forever {
int result = QT_READ(m_fd, reinterpret_cast
if (result == 0) {
qWarning("evdevmouse: Got EOF from the input device");
return;
} else if (result < 0) {
if (errno != EINTR && errno != EAGAIN) {
qErrnoWarning(errno, "evdevmouse: Could not read from input device");
// If the device got disconnected, stop reading, otherwise we get flooded
// by the above error over and over again.
if (errno == ENODEV) {
disconnect(m_notify, 0, 0, 0);
delete m_notify;
m_notify = nullptr;
qt_safe_close(m_fd);
m_fd = -1;
while(1)
{
m_fd = qt_safe_open(m_device.toLocal8Bit().constData(), O_RDONLY | O_NDELAY, 0);
if(m_fd >= 0)
{
m_notify = new QSocketNotifier(m_fd, QSocketNotifier::Read, this);
connect(m_notify, &QSocketNotifier::activated,
this, &QEvdevMouseHandler::readMouseData);
return;
}
}
}
return;
}
} else {
n += result;
if (n % sizeof(buffer[0]) == 0)
break;
}
}
n /= sizeof(buffer[0]);
for (int i = 0; i < n; ++i) {
struct ::input_event *data = &buffer[i];
if (data->type == EV_ABS) {
// Touchpads: store the absolute position for now, will calculate a relative one later.
if (data->code == ABS_X && m_x != data->value) {
m_x = data->value;
posChanged = true;
} else if (data->code == ABS_Y && m_y != data->value) {
m_y = data->value;
posChanged = true;
}
} else if (data->type == EV_REL) {
QPoint delta;
if (data->code == REL_X) {
m_x += data->value;
posChanged = true;
} else if (data->code == REL_Y) {
m_y += data->value;
posChanged = true;
} else if (!m_hiResWheel && data->code == REL_WHEEL) {
// data->value: positive == up, negative == down
delta.setY(120 * data->value);
emit handleWheelEvent(delta);
#ifdef REL_WHEEL_HI_RES
} else if (data->code == REL_WHEEL_HI_RES) {
delta.setY(data->value);
emit handleWheelEvent(delta);
#endif
} else if (!m_hiResHWheel && data->code == REL_HWHEEL) {
// data->value: positive == right, negative == left
delta.setX(-120 * data->value);
emit handleWheelEvent(delta);
#ifdef REL_HWHEEL_HI_RES
} else if (data->code == REL_HWHEEL_HI_RES) {
delta.setX(-data->value);
emit handleWheelEvent(delta);
#endif
}
} else if (data->type == EV_KEY && data->code == BTN_TOUCH) {
// We care about touchpads only, not touchscreens -> don't map to button press.
// Need to invalidate prevx/y however to get proper relative pos.
m_prevInvalid = true;
} else if (data->type == EV_KEY && data->code >= BTN_LEFT && data->code <= BTN_JOYSTICK) {
Qt::MouseButton button = Qt::NoButton;
// BTN_LEFT == 0x110 in kernel's input.h
// The range of possible mouse buttons ends just before BTN_JOYSTICK, value 0x120.
switch (data->code) {
case 0x110: button = Qt::LeftButton; break; // BTN_LEFT
case 0x111: button = Qt::RightButton; break;
case 0x112: button = Qt::MiddleButton; break;
case 0x113: button = Qt::ExtraButton1; break; // AKA Qt::BackButton
case 0x114: button = Qt::ExtraButton2; break; // AKA Qt::ForwardButton
case 0x115: button = Qt::ExtraButton3; break; // AKA Qt::TaskButton
case 0x116: button = Qt::ExtraButton4; break;
case 0x117: button = Qt::ExtraButton5; break;
case 0x118: button = Qt::ExtraButton6; break;
case 0x119: button = Qt::ExtraButton7; break;
case 0x11a: button = Qt::ExtraButton8; break;
case 0x11b: button = Qt::ExtraButton9; break;
case 0x11c: button = Qt::ExtraButton10; break;
case 0x11d: button = Qt::ExtraButton11; break;
case 0x11e: button = Qt::ExtraButton12; break;
case 0x11f: button = Qt::ExtraButton13; break;
}
m_buttons.setFlag(button, data->value);
m_button = button;
m_eventType = data->value == 0 ? QEvent::MouseButtonRelease : QEvent::MouseButtonPress;
btnChanged = true;
} else if (data->type == EV_SYN && data->code == SYN_REPORT) {
if (btnChanged) {
btnChanged = posChanged = false;
sendMouseEvent();
pendingMouseEvent = false;
} else if (posChanged) {
m_eventType = QEvent::MouseMove;
posChanged = false;
if (m_compression) {
pendingMouseEvent = true;
eventCompressCount++;
} else {
sendMouseEvent();
}
}
} else if (data->type == EV_MSC && data->code == MSC_SCAN) {
// kernel encountered an unmapped key - just ignore it
continue;
}
}
if (m_compression && pendingMouseEvent) {
int distanceSquared = (m_x - m_prevx)*(m_x - m_prevx) + (m_y - m_prevy)*(m_y - m_prevy);
if (distanceSquared > m_jitterLimitSquared)
sendMouseEvent();
}
}
QT_END_NAMESPACE
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