kis_input_manager_p.cpp

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/*
 *  SPDX-FileCopyrightText: 2015 Michael Abrahams <miabraha@gmail.com>
 *
 *  SPDX-License-Identifier: GPL-2.0-or-later
 */
 
#include "kis_input_manager_p.h"
 
#include <QMap>
#include <QApplication>
#include <QScopedPointer>
#include <QtGlobal>
 
#include <boost/preprocessor/repeat_from_to.hpp>
 
#include "kis_input_manager.h"
#include "kis_config.h"
#include "kis_abstract_input_action.h"
#include "kis_tool_invocation_action.h"
#include "kis_stroke_shortcut.h"
#include "kis_touch_shortcut.h"
#include "kis_native_gesture_shortcut.h"
#include "kis_input_profile_manager.h"
#include "kis_extended_modifiers_mapper.h"
 
#include "kis_zoom_and_rotate_action.h"
#include "kis_popup_palette.h"
#include "config-qt-patches-present.h"
 
 
static bool isMouseEventType(QEvent::Type t)
{
    return (t == QEvent::MouseMove ||
            t == QEvent::MouseButtonPress ||
            t == QEvent::MouseButtonRelease ||
            t == QEvent::MouseButtonDblClick);
}
 
KisInputManager::Private::EventEater::EventEater()
{
    KisConfig cfg(true);
    activateSecondaryButtonsWorkaround = cfg.useRightMiddleTabletButtonWorkaround();
}
 
bool KisInputManager::Private::EventEater::eventFilter(QObject* target, QEvent* event )
{
    Q_UNUSED(target);
 
    auto debugEvent = [&](int i) {
        if (KisTabletDebugger::instance()->debugEnabled()) {
            QString pre = QString("[BLOCKED %1:]").arg(i);
            QMouseEvent *ev = static_cast<QMouseEvent*>(event);
            dbgTablet << KisTabletDebugger::instance()->eventToString(*ev, pre);
        }
    };
 
    auto debugTabletEvent = [&](int i) {
        if (KisTabletDebugger::instance()->debugEnabled()) {
            QString pre = QString("[BLOCKED %1:]").arg(i);
            QTabletEvent *ev = static_cast<QTabletEvent*>(event);
            dbgTablet << KisTabletDebugger::instance()->eventToString(*ev, pre);
        }
    };
 
    auto debugTouchEvent = [&](int i) {
        if (KisTabletDebugger::instance()->debugEnabled()) {
            QString pre = QString("[BLOCKED %1:]").arg(i);
            QTouchEvent *ev = static_cast<QTouchEvent*>(event);
            dbgTablet << KisTabletDebugger::instance()->eventToString(*ev, pre);
        }
    };
 
    if (peckish && event->type() == QEvent::MouseButtonPress
        // Drop one mouse press following tabletPress or touchBegin
        && (static_cast<QMouseEvent*>(event)->button() == Qt::LeftButton)) {
        peckish = false;
        debugEvent(1);
        return true;
    }
 
    if (activateSecondaryButtonsWorkaround) {
        if (event->type() == QEvent::TabletPress ||
                event->type() == QEvent::TabletRelease) {
 
            QTabletEvent *te = static_cast<QTabletEvent*>(event);
            if (te->button() != Qt::LeftButton) {
                debugTabletEvent(3);
                return true;
            }
        } else if (event->type() == QEvent::MouseButtonPress ||
                   event->type() == QEvent::MouseButtonRelease ||
                   event->type() == QEvent::MouseButtonDblClick) {
 
            QMouseEvent *me = static_cast<QMouseEvent*>(event);
            if (me->button() != Qt::LeftButton) {
                return false;
            }
        }
    }
 
    if (isMouseEventType(event->type()) &&
               (hungry
            // On Mac, we need mouse events when the tablet is in proximity, but not pressed down
            // since tablet move events are not generated until after tablet press.
            #ifndef Q_OS_MAC
                || (eatSyntheticEvents && static_cast<QMouseEvent*>(event)->source() != Qt::MouseEventNotSynthesized)
            #endif
                )) {
        // Drop mouse events if enabled or event was synthetic & synthetic events are disabled
        debugEvent(2);
        return true;
    }
 
    if (eatTouchEvents && event->type() == QEvent::TouchBegin) {
        // Drop touch events. If QEvent::TouchBegin is ignored, we won't
        // receive further touch events until the next TouchBegin.
        debugTouchEvent(3);
        event->ignore();
        return true;
    }
 
    return false; // All clear - let this one through!
}
 
 
void KisInputManager::Private::EventEater::activate()
{
    if (!hungry && (KisTabletDebugger::instance()->debugEnabled())) {
        dbgTablet << "Start blocking mouse events";
    }
    hungry = true;
}
 
void KisInputManager::Private::EventEater::deactivate()
{
    if (hungry && (KisTabletDebugger::instance()->debugEnabled())) {
        dbgTablet << "Stop blocking mouse events";
    }
    hungry = false;
}
 
void KisInputManager::Private::EventEater::eatOneMousePress()
{
    // Enable on other platforms if getting full-pressure splotches
    peckish = true;
}
 
void KisInputManager::Private::EventEater::startBlockingTouch()
{
    eatTouchEvents = true;
}
 
void KisInputManager::Private::EventEater::stopBlockingTouch()
{
    eatTouchEvents = false;
}
 
bool KisInputManager::Private::ignoringQtCursorEvents()
{
    return eventEater.hungry;
}
 
void KisInputManager::Private::setMaskSyntheticEvents(bool value)
{
    eventEater.eatSyntheticEvents = value;
}
 
KisInputManager::Private::Private(KisInputManager *qq)
    : q(qq)
    , moveEventCompressor(10 /* ms */,
                          KisSignalCompressor::FIRST_ACTIVE,
                          KisSignalCompressor::ADDITIVE_INTERVAL)
    , priorityEventFilterSeqNo(0)
    , popupWidget(nullptr)
    , canvasSwitcher(this, qq)
{
    KisConfig cfg(true);
 
    moveEventCompressor.setDelay(cfg.tabletEventsDelay());
    testingAcceptCompressedTabletEvents = cfg.testingAcceptCompressedTabletEvents();
    testingCompressBrushEvents = cfg.testingCompressBrushEvents();
 
    if (cfg.trackTabletEventLatency()) {
        tabletLatencyTracker = new TabletLatencyTracker();
    }
 
    matcher.setInputActionGroupsMaskCallback(
        [this] () {
            return this->canvas ? this->canvas->inputActionGroupsMaskInterface()->inputActionGroupsMask() : AllActionGroup;
        });
 
#ifdef Q_OS_MACOS
    useUnbalancedKeyPressEventWorkaround = true;
#endif
 
#if defined Q_OS_LINUX &&  !KRITA_QT_HAS_UNBALANCED_KEY_PRESS_RELEASE_PATCH
    useUnbalancedKeyPressEventWorkaround = true;
#endif
 
    if (qEnvironmentVariableIsSet("KRITA_FIX_UNBALANCED_KEY_EVENTS")) {
        useUnbalancedKeyPressEventWorkaround = qEnvironmentVariableIntValue("KRITA_FIX_UNBALANCED_KEY_EVENTS");
    }
}
 
static const int InputWidgetsThreshold = 2000;
static const int OtherWidgetsThreshold = 400;
 
KisInputManager::Private::CanvasSwitcher::CanvasSwitcher(Private *_d, QObject *p)
    : QObject(p),
      d(_d),
      eatOneMouseStroke(false),
      focusSwitchThreshold(InputWidgetsThreshold)
{
}
 
void KisInputManager::Private::CanvasSwitcher::setupFocusThreshold(QObject* object)
{
    QWidget *widget = qobject_cast<QWidget*>(object);
    KIS_SAFE_ASSERT_RECOVER_RETURN(widget);
 
    thresholdConnections.clear();
    thresholdConnections.addConnection(&focusSwitchThreshold, SIGNAL(timeout()), widget, SLOT(setFocus()));
}
 
void KisInputManager::Private::CanvasSwitcher::addCanvas(KisCanvas2 *canvas)
{
    if (!canvas) return;
 
    QObject *canvasWidget = canvas->canvasWidget();
 
    if (!canvasResolver.contains(canvasWidget)) {
        canvasResolver.insert(canvasWidget, canvas);
    } else {
        // just a sanity cheek to find out if we are
        // trying to add two canvases concurrently.
        KIS_SAFE_ASSERT_RECOVER_NOOP(d->canvas == canvas);
    }
 
    if (canvas != d->canvas) {
        d->q->setupAsEventFilter(canvasWidget);
        canvasWidget->installEventFilter(this);
 
        setupFocusThreshold(canvasWidget);
        focusSwitchThreshold.setEnabled(false);
 
        d->canvas = canvas;
        d->toolProxy = qobject_cast<KisToolProxy*>(canvas->toolProxy());
    }
}
 
void KisInputManager::Private::CanvasSwitcher::removeCanvas(KisCanvas2 *canvas)
{
    QObject *widget = canvas->canvasWidget();
 
    canvasResolver.remove(widget);
 
    if (d->eventsReceiver == widget) {
        d->q->setupAsEventFilter(0);
    }
 
    widget->removeEventFilter(this);
 
    if (d->canvas == canvas) {
        d->canvas = 0;
        d->toolProxy = 0;
    }
}
 
bool isInputWidget(QWidget *w)
{
    if (!w) return false;
 
 
    QList<QLatin1String> types;
    types << QLatin1String("QAbstractSlider");
    types << QLatin1String("QAbstractSpinBox");
    types << QLatin1String("QLineEdit");
    types << QLatin1String("QTextEdit");
    types << QLatin1String("QPlainTextEdit");
    types << QLatin1String("QComboBox");
    types << QLatin1String("QKeySequenceEdit");
 
    Q_FOREACH (const QLatin1String &type, types) {
        if (w->inherits(type.data())) {
            return true;
        }
    }
 
    return false;
}
 
bool KisInputManager::Private::CanvasSwitcher::eventFilter(QObject* object, QEvent* event )
{
    if (canvasResolver.contains(object)) {
        switch (event->type()) {
        case QEvent::FocusIn: {
            QFocusEvent *fevent = static_cast<QFocusEvent*>(event);
            KisCanvas2 *canvas = canvasResolver.value(object);
 
            // only relevant canvases from the same main window should be
            // registered in the switcher
            KIS_SAFE_ASSERT_RECOVER_BREAK(canvas);
 
            if (canvas != d->canvas) {
                eatOneMouseStroke = 2 * (fevent->reason() == Qt::MouseFocusReason);
            }
 
            d->canvas = canvas;
            d->toolProxy = qobject_cast<KisToolProxy*>(canvas->toolProxy());
 
            d->q->setupAsEventFilter(object);
 
            object->removeEventFilter(this);
            object->installEventFilter(this);
 
            setupFocusThreshold(object);
            focusSwitchThreshold.setEnabled(false);
 
            const QPoint globalPos = QCursor::pos();
            const QPoint localPos = d->canvas->canvasWidget()->mapFromGlobal(globalPos);
            QWidget *canvasWindow = d->canvas->canvasWidget()->window();
            const QPoint windowsPos = canvasWindow ? canvasWindow->mapFromGlobal(globalPos) : localPos;
 
            QEnterEvent event(localPos, windowsPos, globalPos);
            d->q->eventFilter(object, &event);
            break;
        }
        case QEvent::FocusOut: {
            focusSwitchThreshold.setEnabled(true);
            break;
        }
        case QEvent::Enter: {
            break;
        }
        case QEvent::Leave: {
            focusSwitchThreshold.stop();
            break;
        }
        case QEvent::Wheel: {
            QWidget *widget = static_cast<QWidget*>(object);
            widget->setFocus();
            break;
        }
        case QEvent::MouseButtonPress:
        case QEvent::MouseButtonRelease:
        case QEvent::TabletPress:
        case QEvent::TabletRelease:
            focusSwitchThreshold.forceDone();
 
            if (eatOneMouseStroke) {
                eatOneMouseStroke--;
                return true;
            }
            break;
        case QEvent::MouseButtonDblClick:
            focusSwitchThreshold.forceDone();
            if (eatOneMouseStroke) {
                return true;
            }
            break;
        case QEvent::MouseMove:
        case QEvent::TabletMove: {
            QWidget *widget = static_cast<QWidget*>(object);
 
            if (!widget->hasFocus()) {
                const int delay =
                    isInputWidget(QApplication::focusWidget()) ?
                    InputWidgetsThreshold : OtherWidgetsThreshold;
 
                focusSwitchThreshold.setDelayThreshold(delay);
                focusSwitchThreshold.start();
            }
        }
            break;
        default:
            break;
        }
    }
    return QObject::eventFilter(object, event);
}
 
KisInputManager::Private::ProximityNotifier::ProximityNotifier(KisInputManager::Private *_d, QObject *p)
    : QObject(p), d(_d)
{}
 
bool KisInputManager::Private::ProximityNotifier::eventFilter(QObject* object, QEvent* event )
{
    switch (event->type()) {
    case QEvent::TabletEnterProximity:
        d->debugEvent<QEvent, false>(event);
        // Tablet proximity events are unreliable AND fake mouse events do not
        // necessarily come after tablet events, so this is insufficient.
        // d->eventEater.eatOneMousePress();
 
        // Qt sends fake mouse events instead of hover events, so not very useful.
        // Don't block mouse events on tablet since tablet move events are not generated until
        // after tablet press.
#ifndef Q_OS_MACOS
        d->blockMouseEvents();
#endif
        break;
    case QEvent::TabletLeaveProximity:
        d->debugEvent<QEvent, false>(event);
        d->allowMouseEvents();
        break;
#ifdef Q_OS_WIN
    case QEvent::KeyPress:
    case QEvent::KeyRelease:
    case QEvent::ShortcutOverride:
        if (d->ignoreHighFunctionKeys) {
            QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
            int key = keyEvent->key();
 
            if (key >= Qt::Key_F13 && key <= Qt::Key_F35) {
                if (KisTabletDebugger::instance()->debugEnabled()) {
                    const QString pre = "[BLOCKED HIGH F-KEY]";
                    dbgTablet << KisTabletDebugger::instance()->eventToString(*keyEvent, pre);
                }
                return true;
            }
            break;
        }
#endif /* Q_OS_WIN */
    default:
        break;
    }
    return QObject::eventFilter(object, event);
}
 
#define EXTRA_BUTTON(z, n, _) \
    if(buttons & Qt::ExtraButton##n) { \
        buttonSet << Qt::ExtraButton##n; \
    }
 
void KisInputManager::Private::addStrokeShortcut(KisAbstractInputAction* action, int index,
                                                 const QList<Qt::Key> &modifiers,
                                                 Qt::MouseButtons buttons)
{
    KisStrokeShortcut *strokeShortcut =
        new KisStrokeShortcut(action, index);
 
    QSet<Qt::MouseButton> buttonSet;
    if(buttons & Qt::LeftButton) {
        buttonSet << Qt::LeftButton;
    }
    if(buttons & Qt::RightButton) {
        buttonSet << Qt::RightButton;
    }
    if(buttons & Qt::MiddleButton) {
        buttonSet << Qt::MiddleButton;
    }
 
BOOST_PP_REPEAT_FROM_TO(1, 25, EXTRA_BUTTON, _)
 
    if (!buttonSet.empty()) {
        strokeShortcut->setButtons(QSet<Qt::Key>(modifiers.cbegin(), modifiers.cend()), buttonSet);
        matcher.addShortcut(strokeShortcut);
    }
    else {
        delete strokeShortcut;
    }
}
 
void KisInputManager::Private::addKeyShortcut(KisAbstractInputAction* action, int index,
                                              const QList<Qt::Key> &keys)
{
    if (keys.size() == 0) return;
 
    KisSingleActionShortcut *keyShortcut =
        new KisSingleActionShortcut(action, index);
 
    //Note: Ordering is important here, Shift + V is different from V + Shift,
    //which is the reason we use the last key here since most users will enter
    //shortcuts as "Shift + V". Ideally this should not happen, but this is
    //the way the shortcut matcher is currently implemented.
    QList<Qt::Key> allKeys = keys;
    Qt::Key key = allKeys.takeLast();
    QSet<Qt::Key> modifiers = QSet<Qt::Key>(allKeys.begin(), allKeys.end());
    keyShortcut->setKey(modifiers, key);
    matcher.addShortcut(keyShortcut);
}
 
void KisInputManager::Private::addWheelShortcut(KisAbstractInputAction* action, int index,
                                                const QList<Qt::Key> &modifiers,
                                                KisShortcutConfiguration::MouseWheelMovement wheelAction)
{
    QScopedPointer<KisSingleActionShortcut> keyShortcut(
        new KisSingleActionShortcut(action, index));
 
    KisSingleActionShortcut::WheelAction a;
    switch(wheelAction) {
    case KisShortcutConfiguration::WheelUp:
        a = KisSingleActionShortcut::WheelUp;
        break;
    case KisShortcutConfiguration::WheelDown:
        a = KisSingleActionShortcut::WheelDown;
        break;
    case KisShortcutConfiguration::WheelLeft:
        a = KisSingleActionShortcut::WheelLeft;
        break;
    case KisShortcutConfiguration::WheelRight:
        a = KisSingleActionShortcut::WheelRight;
        break;
    case KisShortcutConfiguration::WheelTrackpad:
        a = KisSingleActionShortcut::WheelTrackpad;
        break;
    default:
        return;
    }
    keyShortcut->setWheel(QSet<Qt::Key>(modifiers.begin(), modifiers.end()), a);
    matcher.addShortcut(keyShortcut.take());
}
 
void KisInputManager::Private::addTouchShortcut(KisAbstractInputAction* action, int index, KisShortcutConfiguration::GestureAction gesture)
{
    KisTouchShortcut *shortcut = new KisTouchShortcut(action, index, gesture);
    dbgKrita << "TouchAction:" << action->name();
    switch(gesture) {
#ifndef Q_OS_MACOS
    case KisShortcutConfiguration::OneFingerTap:
    case KisShortcutConfiguration::OneFingerDrag:
        // Touch painting takes precedence over one-finger touch shortcuts, so
        // disable this type of shortcut when touch painting is active.
        shortcut->setDisableOnTouchPainting(true);
        shortcut->setMinimumTouchPoints(1);
        shortcut->setMaximumTouchPoints(1);
        break;
    case KisShortcutConfiguration::TwoFingerTap:
    case KisShortcutConfiguration::TwoFingerDrag:
        shortcut->setMinimumTouchPoints(2);
        shortcut->setMaximumTouchPoints(2);
        break;
    case KisShortcutConfiguration::ThreeFingerTap:
    case KisShortcutConfiguration::ThreeFingerDrag:
        shortcut->setMinimumTouchPoints(3);
        shortcut->setMaximumTouchPoints(3);
        break;
    case KisShortcutConfiguration::FourFingerTap:
    case KisShortcutConfiguration::FourFingerDrag:
        shortcut->setMinimumTouchPoints(4);
        shortcut->setMaximumTouchPoints(4);
        break;
    case KisShortcutConfiguration::FiveFingerTap:
    case KisShortcutConfiguration::FiveFingerDrag:
        shortcut->setMinimumTouchPoints(5);
        shortcut->setMaximumTouchPoints(5);
#endif
    default:
        break;
    }
    matcher.addShortcut(shortcut);
}
 
bool KisInputManager::Private::addNativeGestureShortcut(KisAbstractInputAction* action, int index, KisShortcutConfiguration::GestureAction gesture)
{
    // Qt5 only implements QNativeGestureEvent for macOS
    Qt::NativeGestureType type;
    switch (gesture) {
#ifdef Q_OS_MACOS
        case KisShortcutConfiguration::PinchGesture:
            type = Qt::ZoomNativeGesture;
            break;
        case KisShortcutConfiguration::PanGesture:
            type = Qt::PanNativeGesture;
            break;
        case KisShortcutConfiguration::RotateGesture:
            type = Qt::RotateNativeGesture;
            break;
        case KisShortcutConfiguration::SmartZoomGesture:
            type = Qt::SmartZoomNativeGesture;
            break;
#endif
        default:
            return false;
    }
 
    KisNativeGestureShortcut *shortcut = new KisNativeGestureShortcut(action, index, type);
    matcher.addShortcut(shortcut);
    return true;
}
 
void KisInputManager::Private::setupActions()
{
    QList<KisAbstractInputAction*> actions = KisInputProfileManager::instance()->actions();
    Q_FOREACH (KisAbstractInputAction *action, actions) {
        KisToolInvocationAction *toolAction =
            dynamic_cast<KisToolInvocationAction*>(action);
 
        if(toolAction) {
            defaultInputAction = toolAction;
        }
    }
 
    connect(KisInputProfileManager::instance(), SIGNAL(currentProfileChanged()), q, SLOT(profileChanged()));
    if(KisInputProfileManager::instance()->currentProfile()) {
        q->profileChanged();
    }
}
 
bool KisInputManager::Private::processUnhandledEvent(QEvent *event)
{
    bool retval = false;
 
    if (forwardAllEventsToTool ||
        event->type() == QEvent::KeyPress ||
        event->type() == QEvent::KeyRelease) {
 
        defaultInputAction->processUnhandledEvent(event);
        retval = true;
    }
 
    return retval && !forwardAllEventsToTool;
}
 
#ifdef HAVE_X11
inline QPointF dividePoints(const QPointF &pt1, const QPointF &pt2) {
    return QPointF(pt1.x() / pt2.x(), pt1.y() / pt2.y());
}
 
inline QPointF multiplyPoints(const QPointF &pt1, const QPointF &pt2) {
    return QPointF(pt1.x() * pt2.x(), pt1.y() * pt2.y());
}
#endif
 
void KisInputManager::Private::blockMouseEvents()
{
    eventEater.activate();
}
 
void KisInputManager::Private::allowMouseEvents()
{
#ifdef Q_OS_WIN32
    if (eventEater.hungry && matcher.hasRunningShortcut()) {
        return;
    }
#endif
 
    eventEater.deactivate();
}
 
void KisInputManager::Private::eatOneMousePress()
{
    eventEater.eatOneMousePress();
}
 
void KisInputManager::Private::resetCompressor() {
    compressedMoveEvent.reset();
    moveEventCompressor.stop();
}
 
void KisInputManager::Private::startBlockingTouch()
{
    eventEater.startBlockingTouch();
}
 
void KisInputManager::Private::stopBlockingTouch()
{
    eventEater.stopBlockingTouch();
}
 
bool KisInputManager::Private::handleCompressedTabletEvent(QEvent *event)
{
    bool retval = false;
 
    if (event->type() == QTouchEvent::TouchUpdate && touchHasBlockedPressEvents) {
        matcher.touchUpdateEvent((QTouchEvent *)event);
    } else if (!matcher.pointerMoved(event) && toolProxy && event->type() != QTouchEvent::TouchUpdate) {
        toolProxy->forwardHoverEvent(event);
    }
    retval = true;
    event->setAccepted(true);
 
    return retval;
}
 
void KisInputManager::Private::fixShortcutMatcherModifiersState()
{
    KisExtendedModifiersMapper mapper;
 
    QVector<Qt::Key> newKeys;
    Qt::KeyboardModifiers modifiers = mapper.queryStandardModifiers();
    Q_FOREACH (Qt::Key key, mapper.queryExtendedModifiers()) {
        QKeyEvent kevent(QEvent::ShortcutOverride, key, modifiers);
        newKeys << KisExtendedModifiersMapper::workaroundShiftAltMetaHell(&kevent);
    }
 
    fixShortcutMatcherModifiersState(newKeys, modifiers);
}
 
void KisInputManager::Private::fixShortcutMatcherModifiersState(QVector<Qt::Key> newKeys, Qt::KeyboardModifiers modifiers)
{
    QVector<Qt::Key> danglingKeys = matcher.debugPressedKeys();
 
    matcher.handlePolledKeys(newKeys);
 
    for (auto it = danglingKeys.begin(); it != danglingKeys.end();) {
        if (newKeys.contains(*it)) {
            newKeys.removeOne(*it);
            it = danglingKeys.erase(it);
        } else {
            ++it;
        }
    }
 
    Q_FOREACH (Qt::Key key, danglingKeys) {
        QKeyEvent kevent(QEvent::KeyRelease, key, modifiers);
        processUnhandledEvent(&kevent);
    }
 
    Q_FOREACH (Qt::Key key, newKeys) {
        // just replay the whole sequence
        {
            QKeyEvent kevent(QEvent::ShortcutOverride, key, modifiers);
            processUnhandledEvent(&kevent);
        }
        {
            QKeyEvent kevent(QEvent::KeyPress, key, modifiers);
            processUnhandledEvent(&kevent);
        }
    }
}
 
qint64 KisInputManager::Private::TabletLatencyTracker::currentTimestamp() const
{
    // on OS X, we need to compute the timestamp that compares correctly against the native event timestamp,
    // which seems to be the msecs since system startup. On Linux with WinTab, we produce the timestamp that
    // we compare against ourselves in QWindowSystemInterface.
 
    QElapsedTimer elapsed;
    elapsed.start();
    return elapsed.msecsSinceReference();
}
 
void KisInputManager::Private::TabletLatencyTracker::print(const QString &message)
{
    dbgTablet << qUtf8Printable(message);
}