qiosinputcontext.mm

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// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#include "qiosinputcontext.h"
 
#import <UIKit/UIGestureRecognizerSubclass.h>
 
#include "qiosglobal.h"
#include "qiosintegration.h"
#include "qiosscreen.h"
#include "qiostextresponder.h"
#include "qiosviewcontroller.h"
#include "qioswindow.h"
#include "quiview.h"
 
#include <QtCore/private/qcore_mac_p.h>
 
#include <QGuiApplication>
#include <QtGui/private/qwindow_p.h>
 
// -------------------------------------------------------------------------
 
static QUIView *focusView()
{
    return qApp->focusWindow() ?
        reinterpret_cast<QUIView *>(qApp->focusWindow()->winId()) : 0;
}
 
// -------------------------------------------------------------------------
 
@interface QIOSLocaleListener : NSObject
@end
 
@implementation QIOSLocaleListener
 
- (instancetype)init
{
    if (self = [super init]) {
        NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
        [notificationCenter addObserver:self
            selector:@selector(localeDidChange:)
            name:NSCurrentLocaleDidChangeNotification object:nil];
    }
 
    return self;
}
 
- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    [super dealloc];
}
 
- (void)localeDidChange:(NSNotification *)notification
{
    Q_UNUSED(notification);
    QIOSInputContext::instance()->emitLocaleChanged();
}
 
@end
 
// -------------------------------------------------------------------------
 
@interface QIOSKeyboardListener : UIGestureRecognizer <UIGestureRecognizerDelegate>
@property BOOL hasDeferredScrollToCursor;
@end
 
@implementation QIOSKeyboardListener {
    QT_PREPEND_NAMESPACE(QIOSInputContext) *m_context;
}
 
- (instancetype)initWithQIOSInputContext:(QT_PREPEND_NAMESPACE(QIOSInputContext) *)context
{
    if (self = [super initWithTarget:self action:@selector(gestureStateChanged:)]) {
 
        m_context = context;
 
        self.hasDeferredScrollToCursor = NO;
 
        // UIGestureRecognizer
        self.enabled = NO;
        self.cancelsTouchesInView = NO;
        self.delaysTouchesEnded = NO;
 
#ifndef Q_OS_TVOS
        NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter];
 
        [notificationCenter addObserver:self
            selector:@selector(keyboardWillShow:)
            name:UIKeyboardWillShowNotification object:nil];
        [notificationCenter addObserver:self
            selector:@selector(keyboardWillOrDidChange:)
            name:UIKeyboardDidShowNotification object:nil];
        [notificationCenter addObserver:self
            selector:@selector(keyboardWillHide:)
            name:UIKeyboardWillHideNotification object:nil];
        [notificationCenter addObserver:self
            selector:@selector(keyboardWillOrDidChange:)
            name:UIKeyboardDidHideNotification object:nil];
        [notificationCenter addObserver:self
            selector:@selector(keyboardDidChangeFrame:)
            name:UIKeyboardDidChangeFrameNotification object:nil];
#endif
    }
 
    return self;
}
 
- (void)dealloc
{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
 
    [super dealloc];
}
 
// -------------------------------------------------------------------------
 
- (void)keyboardWillShow:(NSNotification *)notification
{
    [self keyboardWillOrDidChange:notification];
 
    UIResponder *firstResponder = [UIResponder currentFirstResponder];
    if (![firstResponder isKindOfClass:[QIOSTextInputResponder class]])
        return;
 
    // Enable hide-keyboard gesture
    self.enabled = m_context->isInputPanelVisible();
 
    m_context->scrollToCursor();
}
 
- (void)keyboardWillHide:(NSNotification *)notification
{
    [self keyboardWillOrDidChange:notification];
 
    if (self.state != UIGestureRecognizerStateBegan) {
        // Only disable the gesture if the hiding of the keyboard was not caused by it.
        // Otherwise we need to await the final touchEnd callback for doing some clean-up.
        self.enabled = NO;
    }
    m_context->scroll(0);
}
 
- (void)keyboardDidChangeFrame:(NSNotification *)notification
{
    [self keyboardWillOrDidChange:notification];
 
    // If the keyboard was visible and docked from before, this is just a geometry
    // change (normally caused by an orientation change). In that case, update scroll:
    if (m_context->isInputPanelVisible())
        m_context->scrollToCursor();
}
 
- (void)keyboardWillOrDidChange:(NSNotification *)notification
{
    m_context->updateKeyboardState(notification);
}
 
// -------------------------------------------------------------------------
 
- (BOOL)canPreventGestureRecognizer:(UIGestureRecognizer *)other
{
    Q_UNUSED(other);
    return NO;
}
 
- (BOOL)canBePreventedByGestureRecognizer:(UIGestureRecognizer *)other
{
    Q_UNUSED(other);
    return NO;
}
 
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesBegan:touches withEvent:event];
 
    if (!m_context->isInputPanelVisible()) {
        qImDebug("keyboard was hidden by sliding it down, disabling hide-keyboard gesture");
        self.enabled = NO;
        return;
    }
 
    if ([touches count] != 1)
        self.state = UIGestureRecognizerStateFailed;
}
 
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesMoved:touches withEvent:event];
 
    if (self.state != UIGestureRecognizerStatePossible)
        return;
 
    CGPoint touchPoint = [[touches anyObject] locationInView:self.view];
    if (CGRectContainsPoint(m_context->keyboardState().keyboardEndRect, touchPoint))
        self.state = UIGestureRecognizerStateBegan;
}
 
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesEnded:touches withEvent:event];
 
    [self touchesEndedOrCancelled];
}
 
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesCancelled:touches withEvent:event];
 
    [self touchesEndedOrCancelled];
}
 
- (void)touchesEndedOrCancelled
{
    // Defer final state change until next runloop iteration, so that Qt
    // has a chance to process the final touch events first, before we eg.
    // scroll the view.
    dispatch_async(dispatch_get_main_queue (), ^{
        // iOS will transition from began to changed by itself
        Q_ASSERT(self.state != UIGestureRecognizerStateBegan);
 
        if (self.state == UIGestureRecognizerStateChanged)
            self.state = UIGestureRecognizerStateEnded;
        else
            self.state = UIGestureRecognizerStateFailed;
    });
}
 
- (void)gestureStateChanged:(id)sender
{
    Q_UNUSED(sender);
 
    if (self.state == UIGestureRecognizerStateBegan) {
        qImDebug("hide keyboard gesture was triggered");
        UIResponder *firstResponder = [UIResponder currentFirstResponder];
        Q_ASSERT([firstResponder isKindOfClass:[QIOSTextInputResponder class]]);
        [firstResponder resignFirstResponder];
    }
}
 
- (void)reset
{
    [super reset];
 
    if (!m_context->isInputPanelVisible()) {
        qImDebug("keyboard was hidden, disabling hide-keyboard gesture");
        self.enabled = NO;
    } else {
        qImDebug("gesture completed without triggering");
        if (self.hasDeferredScrollToCursor) {
            qImDebug("applying deferred scroll to cursor");
            m_context->scrollToCursor();
        }
    }
 
    self.hasDeferredScrollToCursor = NO;
}
 
@end
 
// -------------------------------------------------------------------------
 
QT_BEGIN_NAMESPACE
 
Qt::InputMethodQueries ImeState::update(Qt::InputMethodQueries properties)
{
    if (!properties)
        return {};
 
    QInputMethodQueryEvent newState(properties);
 
    // Update the focus object that the new state is based on
    focusObject = qApp ? qApp->focusObject() : 0;
 
    if (focusObject)
        QCoreApplication::sendEvent(focusObject, &newState);
 
    Qt::InputMethodQueries updatedProperties;
    for (uint i = 0; i < (sizeof(Qt::ImQueryAll) * CHAR_BIT); ++i) {
        if (Qt::InputMethodQuery property = Qt::InputMethodQuery(int(properties & (1 << i)))) {
            if (newState.value(property) != currentState.value(property)) {
                updatedProperties |= property;
                currentState.setValue(property, newState.value(property));
            }
        }
    }
 
    return updatedProperties;
}
 
// -------------------------------------------------------------------------
 
QIOSInputContext *QIOSInputContext::instance()
{
    return static_cast<QIOSInputContext *>(QIOSIntegration::instance()->inputContext());
}
 
QIOSInputContext::QIOSInputContext()
    : QPlatformInputContext()
    , m_localeListener([QIOSLocaleListener new])
    , m_keyboardHideGesture([[QIOSKeyboardListener alloc] initWithQIOSInputContext:this])
    , m_textResponder(0)
{
    if (isQtApplication()) {
        QIOSScreen *iosScreen = static_cast<QIOSScreen*>(QGuiApplication::primaryScreen()->handle());
        [iosScreen->uiWindow() addGestureRecognizer:m_keyboardHideGesture];
    }
 
    connect(qGuiApp, &QGuiApplication::focusWindowChanged, this, &QIOSInputContext::focusWindowChanged);
}
 
QIOSInputContext::~QIOSInputContext()
{
    [m_localeListener release];
    [m_keyboardHideGesture.view removeGestureRecognizer:m_keyboardHideGesture];
    [m_keyboardHideGesture release];
 
    [m_textResponder release];
}
 
void QIOSInputContext::showInputPanel()
{
    // No-op, keyboard controlled fully by platform based on focus
    qImDebug("can't show virtual keyboard without a focus object, ignoring");
}
 
void QIOSInputContext::hideInputPanel()
{
    if (![m_textResponder isFirstResponder]) {
        qImDebug("QIOSTextInputResponder is not first responder, ignoring");
        return;
    }
 
    if (qGuiApp->focusObject() != m_imeState.focusObject) {
        qImDebug("current focus object does not match IM state, likely hiding from focusOut event, so ignoring");
        return;
    }
 
    qImDebug("hiding VKB as requested by QInputMethod::hide()");
    [m_textResponder resignFirstResponder];
}
 
void QIOSInputContext::clearCurrentFocusObject()
{
    if (QWindow *focusWindow = qApp->focusWindow())
        static_cast<QWindowPrivate *>(QObjectPrivate::get(focusWindow))->clearFocusObject();
}
 
// -------------------------------------------------------------------------
 
void QIOSInputContext::updateKeyboardState(NSNotification *notification)
{
#ifdef Q_OS_TVOS
    Q_UNUSED(notification);
#else
    static CGRect currentKeyboardRect = CGRectZero;
 
    KeyboardState previousState = m_keyboardState;
 
    if (notification) {
        NSDictionary *userInfo = [notification userInfo];
 
        CGRect frameBegin = [[userInfo objectForKey:UIKeyboardFrameBeginUserInfoKey] CGRectValue];
        CGRect frameEnd = [[userInfo objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
 
        bool atEndOfKeyboardTransition = [notification.name rangeOfString:@"Did"].location != NSNotFound;
 
        currentKeyboardRect = atEndOfKeyboardTransition ? frameEnd : frameBegin;
 
        // The isInputPanelVisible() property is based on whether or not the virtual keyboard
        // is visible on screen, and does not follow the logic of the iOS WillShow and WillHide
        // notifications which are not emitted for undocked keyboards, and are buggy when dealing
        // with input-accessory-views. The reason for using frameEnd here (the future state),
        // instead of the current state reflected in frameBegin, is that QInputMethod::isVisible()
        // is documented to reflect the future state in the case of animated transitions.
        m_keyboardState.keyboardVisible = CGRectIntersectsRect(frameEnd, [UIScreen mainScreen].bounds);
 
        // Used for auto-scroller, and will be used for animation-signal in the future
        m_keyboardState.keyboardEndRect = frameEnd;
 
        if (m_keyboardState.animationCurve < 0) {
            // We only set the animation curve the first time it has a valid value, since iOS will sometimes report
            // an invalid animation curve even if the keyboard is animating, and we don't want to overwrite the
            // curve in that case.
            m_keyboardState.animationCurve = UIViewAnimationCurve([[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] integerValue]);
        }
 
        m_keyboardState.animationDuration = [[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue];
        m_keyboardState.keyboardAnimating = m_keyboardState.animationDuration > 0 && !atEndOfKeyboardTransition;
 
        qImDebug() << qPrintable(QString::fromNSString(notification.name)) << "from" << QRectF::fromCGRect(frameBegin) << "to" << QRectF::fromCGRect(frameEnd)
                   << "(curve =" << m_keyboardState.animationCurve << "duration =" << m_keyboardState.animationDuration << "s)";
    } else {
        qImDebug("No notification to update keyboard state based on, just updating keyboard rect");
    }
 
    if (!focusView() || CGRectIsEmpty(currentKeyboardRect))
        m_keyboardState.keyboardRect = QRectF();
    else // QInputmethod::keyboardRectangle() is documented to be in window coordinates.
        m_keyboardState.keyboardRect = QRectF::fromCGRect([focusView() convertRect:currentKeyboardRect fromView:nil]);
 
    // Emit for all changed properties
    if (m_keyboardState.keyboardVisible != previousState.keyboardVisible)
        emitInputPanelVisibleChanged();
    if (m_keyboardState.keyboardAnimating != previousState.keyboardAnimating)
        emitAnimatingChanged();
    if (m_keyboardState.keyboardRect != previousState.keyboardRect)
        emitKeyboardRectChanged();
#endif
}
 
bool QIOSInputContext::isInputPanelVisible() const
{
    return m_keyboardState.keyboardVisible;
}
 
bool QIOSInputContext::isAnimating() const
{
    return m_keyboardState.keyboardAnimating;
}
 
QRectF QIOSInputContext::keyboardRect() const
{
    return m_keyboardState.keyboardRect;
}
 
// -------------------------------------------------------------------------
 
UIView *QIOSInputContext::scrollableRootView()
{
    if (!m_keyboardHideGesture.view)
        return 0;
 
    UIWindow *window = static_cast<UIWindow*>(m_keyboardHideGesture.view);
    if (![window.rootViewController isKindOfClass:[QIOSViewController class]])
        return 0;
 
    return window.rootViewController.view;
}
 
void QIOSInputContext::scrollToCursor()
{
    if (!isQtApplication())
        return;
 
    if (m_keyboardHideGesture.state == UIGestureRecognizerStatePossible && m_keyboardHideGesture.numberOfTouches == 1) {
        // Don't scroll to the cursor if the user is touching the screen and possibly
        // trying to trigger the hide-keyboard gesture.
        qImDebug("deferring scrolling to cursor as we're still waiting for a possible gesture");
        m_keyboardHideGesture.hasDeferredScrollToCursor = YES;
        return;
    }
 
    UIView *rootView = scrollableRootView();
    if (!rootView)
        return;
 
    if (!focusView())
        return;
 
    if (rootView.window != focusView().window)
        return;
 
    // We only support auto-scroll for docked keyboards for now, so make sure that's the case
    if (CGRectGetMaxY(m_keyboardState.keyboardEndRect) != CGRectGetMaxY([UIScreen mainScreen].bounds)) {
        qImDebug("Keyboard not docked, ignoring request to scroll to reveal cursor");
        return;
    }
 
    QPlatformWindow *focusWindow = qApp->focusWindow()->handle();
    QRect windowCurosorRect = QPlatformInputContext::cursorRectangle().toRect();
    QRect cursorRect = QRect(focusWindow->mapToGlobal(windowCurosorRect.topLeft()), windowCurosorRect.size());
 
    // We explicitly ask for the geometry of the screen instead of the availableGeometry,
    // as we hide the status bar when scrolling the screen, so the available geometry will
    // include the space taken by the status bar at the moment.
    QRect screenGeometry = focusWindow->screen()->geometry();
 
    if (!cursorRect.isNull()) {
         // Add some padding so that the cursor does not end up directly above the keyboard
        static const int kCursorRectPadding = 20;
        cursorRect.adjust(0, -kCursorRectPadding, 0, kCursorRectPadding);
 
        // Make sure the cursor rect is still within the screen geometry after padding
        cursorRect &= screenGeometry;
    }
 
    QRect keyboardGeometry = QRectF::fromCGRect(m_keyboardState.keyboardEndRect).toRect();
    QRect availableGeometry = (QRegion(screenGeometry) - keyboardGeometry).boundingRect();
 
    if (!cursorRect.isNull() && !availableGeometry.contains(cursorRect)) {
        qImDebug() << "cursor rect" << cursorRect << "not fully within" << availableGeometry;
        int scrollToCenter = -(availableGeometry.center() - cursorRect.center()).y();
        int scrollToBottom = focusWindow->screen()->geometry().bottom() - availableGeometry.bottom();
        scroll(qMin(scrollToCenter, scrollToBottom));
    } else {
        scroll(0);
    }
}
 
void QIOSInputContext::scroll(int y)
{
    Q_ASSERT(y >= 0);
 
    UIView *rootView = scrollableRootView();
    if (!rootView)
        return;
 
    if (qt_apple_isApplicationExtension()) {
        qWarning() << "can't scroll root view in application extension";
        return;
    }
 
    CATransform3D translationTransform = CATransform3DMakeTranslation(0.0, -y, 0.0);
    if (CATransform3DEqualToTransform(translationTransform, rootView.layer.sublayerTransform))
        return;
 
    qImDebug() << "scrolling root view to y =" << -y;
 
    QPointer<QIOSInputContext> self = this;
    [UIView animateWithDuration:m_keyboardState.animationDuration delay:0
        options:(m_keyboardState.animationCurve << 16) | UIViewAnimationOptionBeginFromCurrentState
        animations:^{
            // The sublayerTransform property of CALayer is not implicitly animated for a
            // layer-backed view, even inside a UIView animation block, so we need to set up
            // an explicit CoreAnimation animation. Since there is no predefined media timing
            // function that matches the custom keyboard animation curve we cheat by asking
            // the view for an animation of another property, which will give us an animation
            // that matches the parameters we passed to [UIView animateWithDuration] above.
            // The reason we ask for the animation of 'backgroundColor' is that it's a simple
            // property that will not return a compound animation, like eg. bounds will.
            NSObject *action = (NSObject*)[rootView actionForLayer:rootView.layer forKey:@"backgroundColor"];
 
            CABasicAnimation *animation;
            if ([action isKindOfClass:[CABasicAnimation class]]) {
                animation = static_cast<CABasicAnimation*>(action);
                animation.keyPath = @"sublayerTransform"; // Instead of backgroundColor
            } else {
                animation = [CABasicAnimation animationWithKeyPath:@"sublayerTransform"];
            }
 
            CATransform3D currentSublayerTransform = static_cast<CALayer *>([rootView.layer presentationLayer]).sublayerTransform;
            animation.fromValue = [NSValue valueWithCATransform3D:currentSublayerTransform];
            animation.toValue = [NSValue valueWithCATransform3D:translationTransform];
            [rootView.layer addAnimation:animation forKey:@"AnimateSubLayerTransform"];
            rootView.layer.sublayerTransform = translationTransform;
 
            bool keyboardScrollIsActive = y != 0;
 
            // Raise all known windows to above the status-bar if we're scrolling the screen,
            // while keeping the relative window level between the windows the same.
            NSArray<UIWindow *> *applicationWindows = [qt_apple_sharedApplication() windows];
            static QHash<UIWindow *, UIWindowLevel> originalWindowLevels;
            for (UIWindow *window in applicationWindows) {
                if (keyboardScrollIsActive && !originalWindowLevels.contains(window))
                    originalWindowLevels.insert(window, window.windowLevel);
 
#ifndef Q_OS_TVOS
                UIWindowLevel windowLevelAdjustment = keyboardScrollIsActive ? UIWindowLevelStatusBar : 0;
#else
                UIWindowLevel windowLevelAdjustment = 0;
#endif
                window.windowLevel = originalWindowLevels.value(window) + windowLevelAdjustment;
 
                if (!keyboardScrollIsActive)
                    originalWindowLevels.remove(window);
            }
        }
        completion:^(BOOL){
            if (self) {
                // Scrolling the root view results in the keyboard being moved
                // relative to the focus window, so we need to re-evaluate the
                // keyboard rectangle.
                updateKeyboardState();
            }
        }
    ];
}
 
// -------------------------------------------------------------------------
 
void QIOSInputContext::setFocusObject(QObject *focusObject)
{
    Q_UNUSED(focusObject);
 
    qImDebug() << "new focus object =" << focusObject;
 
    if (QPlatformInputContext::inputMethodAccepted()
            && m_keyboardHideGesture.state == UIGestureRecognizerStateChanged) {
        // A new focus object may be set as part of delivering touch events to
        // application during the hide-keyboard gesture, but we don't want that
        // to result in a new object getting focus and bringing the keyboard up
        // again.
        qImDebug() << "clearing focus object" << focusObject << "as hide-keyboard gesture is active";
        clearCurrentFocusObject();
        return;
    } else if (focusObject == m_imeState.focusObject) {
        qImDebug("same focus object as last update, skipping reset");
        return;
    }
 
    reset();
 
    if (isInputPanelVisible())
        scrollToCursor();
}
 
void QIOSInputContext::focusWindowChanged(QWindow *focusWindow)
{
    Q_UNUSED(focusWindow);
 
    qImDebug() << "new focus window =" << focusWindow;
 
    reset();
 
    // The keyboard rectangle depend on the focus window, so
    // we need to re-evaluate the keyboard state.
    updateKeyboardState();
 
    if (isInputPanelVisible())
        scrollToCursor();
}
 
void QIOSInputContext::update(Qt::InputMethodQueries updatedProperties)
{
    qImDebug() << "fw =" << qApp->focusWindow() << "fo =" << qApp->focusObject();
 
    // Changes to the focus object should always result in a call to setFocusObject(),
    // triggering a reset() which will update all the properties based on the new
    // focus object. We try to detect code paths that fail this assertion and smooth
    // over the situation by doing a manual update of the focus object.
    if (qApp->focusObject() != m_imeState.focusObject && updatedProperties != Qt::ImQueryAll) {
        qWarning() << "stale focus object" << static_cast<void *>(m_imeState.focusObject)
                   << ", doing manual update";
        setFocusObject(qApp->focusObject());
        return;
    }
 
    // Mask for properties that we are interested in and see if any of them changed
    updatedProperties &= (Qt::ImEnabled | Qt::ImHints | Qt::ImQueryInput | Qt::ImEnterKeyType | Qt::ImPlatformData | Qt::ImReadOnly);
 
    // Perform update first, so we can trust the value of inputMethodAccepted()
    Qt::InputMethodQueries changedProperties = m_imeState.update(updatedProperties);
 
    const bool inputIsReadOnly = m_imeState.currentState.value(Qt::ImReadOnly).toBool();
 
    if (inputMethodAccepted() || inputIsReadOnly) {
        if (!m_textResponder || [m_textResponder needsKeyboardReconfigure:changedProperties]) {
            [m_textResponder autorelease];
            if (inputIsReadOnly) {
                qImDebug("creating new read-only text responder");
                m_textResponder = [[QIOSTextResponder alloc] initWithInputContext:this];
            } else {
                qImDebug("creating new read/write text responder");
                m_textResponder = [[QIOSTextInputResponder alloc] initWithInputContext:this];
            }
        } else {
            qImDebug("no need to reconfigure keyboard, just notifying input delegate");
            [m_textResponder notifyInputDelegate:changedProperties];
        }
 
        if (![m_textResponder isFirstResponder]) {
            qImDebug("IM enabled, making text responder first responder");
            [m_textResponder becomeFirstResponder];
        }
 
        if (changedProperties & Qt::ImCursorRectangle)
            scrollToCursor();
    } else if ([m_textResponder isFirstResponder]) {
        qImDebug("IM not enabled, resigning text responder as first responder");
        [m_textResponder resignFirstResponder];
    }
}
 
bool QIOSInputContext::inputMethodAccepted() const
{
    // The IM enablement state is based on the last call to update()
    bool lastKnownImEnablementState = m_imeState.currentState.value(Qt::ImEnabled).toBool();
 
#if !defined(QT_NO_DEBUG)
    // QPlatformInputContext keeps a cached value of the current IM enablement state that is
    // updated by QGuiApplication when the current focus object changes, or by QInputMethod's
    // update() function. If the focus object changes, but the change is not propagated as
    // a signal to QGuiApplication due to bugs in the widget/graphicsview/qml stack, we'll
    // end up with a stale value for QPlatformInputContext::inputMethodAccepted(). To be on
    // the safe side we always use our own cached value to decide if IM is enabled, and try
    // to detect the case where the two values are out of sync.
    if (lastKnownImEnablementState != QPlatformInputContext::inputMethodAccepted())
        qWarning("QPlatformInputContext::inputMethodAccepted() does not match actual focus object IM enablement!");
#endif
 
    return lastKnownImEnablementState;
}
 
void QIOSInputContext::reset()
{
    qImDebug("releasing text responder");
 
    // UIKit will sometimes, for unknown reasons, unset the input delegate on the
    // current text responder. This seems to happen as a result of us calling
    // [self.inputDelegate textDidChange:self] from [m_textResponder reset].
    // But it won't be set to nil directly, only after a character is typed on
    // the input panel after the reset. This strange behavior seems to be related
    // to us overriding [QUIView setInteraction] to ignore UITextInteraction. If we
    // didn't do that, the delegate would be kept. But not overriding that function
    // has its own share of issues, so it seems better to keep that way for now.
    // Instead, we choose to recreate the text responder as a brute-force solution
    // until we have better knowledge of what is going on (or implement the new
    // UITextInteraction protocol).
    const auto oldResponder = m_textResponder;
    [m_textResponder reset];
    [m_textResponder autorelease];
    m_textResponder = nullptr;
 
    update(Qt::ImQueryAll);
 
    // If update() didn't end up creating a new text responder, oldResponder will still be
    // the first responder. In that case we need to resign it, so that the input panel hides.
    // (the input panel will apparently not hide if the first responder is only released).
    if ([oldResponder isFirstResponder]) {
        qImDebug("IM not enabled, resigning autoreleased text responder as first responder");
        [oldResponder resignFirstResponder];
    }
}
 
void QIOSInputContext::commit()
{
    qImDebug("unmarking text");
    [m_textResponder commit];
}
 
QLocale QIOSInputContext::locale() const
{
    return QLocale(QString::fromNSString([[NSLocale currentLocale] objectForKey:NSLocaleIdentifier]));
}
 
QT_END_NAMESPACE