JUCE/modules/juce_gui_basics/native/accessibility/juce_mac_Accessibility.mm

/*
  ==============================================================================

   This file is part of the JUCE 7 technical preview.
   Copyright (c) 2022 - Raw Material Software Limited

   You may use this code under the terms of the GPL v3
   (see www.gnu.org/licenses).

   For the technical preview this file cannot be licensed commercially.

   JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
   EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
   DISCLAIMED.

  ==============================================================================
*/

API_AVAILABLE (macos (10.10))
static void juceFreeAccessibilityPlatformSpecificData (NSAccessibilityElement<NSAccessibility>*)  {}

namespace juce
{

#if ! defined (MAC_OS_X_VERSION_10_13) || MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_13
 using NSAccessibilityRole = NSString*;
 using NSAccessibilityNotificationName = NSString*;
#endif

#define JUCE_NATIVE_ACCESSIBILITY_INCLUDED 1

//==============================================================================
class AccessibilityHandler::AccessibilityNativeImpl
{
public:
    explicit AccessibilityNativeImpl (AccessibilityHandler& handler)
    {
        if (@available (macOS 10.10, *))
            accessibilityElement = AccessibilityElement::create (handler);
    }

    API_AVAILABLE (macos (10.10))
    NSAccessibilityElement<NSAccessibility>* getAccessibilityElement() const noexcept
    {
        return accessibilityElement.get();
    }

private:
    //==============================================================================
    class API_AVAILABLE (macos (10.10)) AccessibilityElement  : public AccessibleObjCClass<NSAccessibilityElement<NSAccessibility>>
    {
    public:
        static Holder create (AccessibilityHandler& handler)
        {
            if (@available (macOS 10.10, *))
            {
                static AccessibilityElement cls;
                Holder element ([cls.createInstance() init]);
                object_setInstanceVariable (element.get(), "handler", &handler);
                return element;
            }

            return {};
        }

    private:
        AccessibilityElement()
        {
            addMethod (@selector (accessibilityNotifiesWhenDestroyed),     getAccessibilityNotifiesWhenDestroyed);
            addMethod (@selector (isAccessibilityElement),                 getIsAccessibilityElement);
            addMethod (@selector (isAccessibilityEnabled),                 getIsAccessibilityEnabled);
            addMethod (@selector (accessibilityWindow),                    getAccessibilityWindow);
            addMethod (@selector (accessibilityTopLevelUIElement),         getAccessibilityWindow);
            addMethod (@selector (accessibilityFocusedUIElement),          getAccessibilityFocusedUIElement);
            addMethod (@selector (accessibilityHitTest:),                  accessibilityHitTest);
            addMethod (@selector (accessibilityParent),                    getAccessibilityParent);
            addMethod (@selector (accessibilityChildren),                  getAccessibilityChildren);
            addMethod (@selector (isAccessibilityFocused),                 getIsAccessibilityFocused);
            addMethod (@selector (setAccessibilityFocused:),               setAccessibilityFocused);
            addMethod (@selector (isAccessibilityModal),                   getIsAccessibilityModal);
            addMethod (@selector (accessibilityFrame),                     getAccessibilityFrame);
            addMethod (@selector (accessibilityRole),                      getAccessibilityRole);
            addMethod (@selector (accessibilitySubrole),                   getAccessibilitySubrole);
            addMethod (@selector (accessibilityTitle),                     getAccessibilityTitle);
            addMethod (@selector (accessibilityLabel),                     getAccessibilityLabel);
            addMethod (@selector (accessibilityHelp),                      getAccessibilityHelp);
            addMethod (@selector (accessibilityValue),                     getAccessibilityValue);
            addMethod (@selector (setAccessibilityValue:),                 setAccessibilityValue);
            addMethod (@selector (accessibilitySelectedChildren),          getAccessibilitySelectedChildren);
            addMethod (@selector (setAccessibilitySelectedChildren:),      setAccessibilitySelectedChildren);
            addMethod (@selector (accessibilityOrientation),               getAccessibilityOrientation);

            addMethod (@selector (accessibilityInsertionPointLineNumber),  getAccessibilityInsertionPointLineNumber);
            addMethod (@selector (accessibilityVisibleCharacterRange),     getAccessibilityVisibleCharacterRange);
            addMethod (@selector (accessibilityNumberOfCharacters),        getAccessibilityNumberOfCharacters);
            addMethod (@selector (accessibilitySelectedText),              getAccessibilitySelectedText);
            addMethod (@selector (accessibilitySelectedTextRange),         getAccessibilitySelectedTextRange);
            addMethod (@selector (accessibilityAttributedStringForRange:), getAccessibilityAttributedStringForRange);
            addMethod (@selector (accessibilityRangeForLine:),             getAccessibilityRangeForLine);
            addMethod (@selector (accessibilityStringForRange:),           getAccessibilityStringForRange);
            addMethod (@selector (accessibilityRangeForPosition:),         getAccessibilityRangeForPosition);
            addMethod (@selector (accessibilityRangeForIndex:),            getAccessibilityRangeForIndex);
            addMethod (@selector (accessibilityFrameForRange:),            getAccessibilityFrameForRange);
            addMethod (@selector (accessibilityLineForIndex:),             getAccessibilityLineForIndex);
            addMethod (@selector (setAccessibilitySelectedTextRange:),     setAccessibilitySelectedTextRange);

            addMethod (@selector (accessibilityRowCount),            getAccessibilityRowCount);
            addMethod (@selector (accessibilityRows),                getAccessibilityRows);
            addMethod (@selector (accessibilitySelectedRows),        getAccessibilitySelectedRows);
            addMethod (@selector (setAccessibilitySelectedRows:),    setAccessibilitySelectedRows);
            addMethod (@selector (accessibilityColumnCount),         getAccessibilityColumnCount);
            addMethod (@selector (accessibilityColumns),             getAccessibilityColumns);
            addMethod (@selector (accessibilitySelectedColumns),     getAccessibilitySelectedColumns);
            addMethod (@selector (setAccessibilitySelectedColumns:), setAccessibilitySelectedColumns);

            addMethod (@selector (accessibilityRowIndexRange),    getAccessibilityRowIndexRange);
            addMethod (@selector (accessibilityColumnIndexRange), getAccessibilityColumnIndexRange);
            addMethod (@selector (accessibilityIndex),            getAccessibilityIndex);
            addMethod (@selector (accessibilityDisclosureLevel),  getAccessibilityDisclosureLevel);
            addMethod (@selector (isAccessibilityExpanded),       getIsAccessibilityExpanded);

            addMethod (@selector (accessibilityPerformIncrement), accessibilityPerformIncrement);
            addMethod (@selector (accessibilityPerformDecrement), accessibilityPerformDecrement);
            addMethod (@selector (accessibilityPerformDelete),    accessibilityPerformDelete);
            addMethod (@selector (accessibilityPerformPress),     accessibilityPerformPress);
            addMethod (@selector (accessibilityPerformShowMenu),  accessibilityPerformShowMenu);
            addMethod (@selector (accessibilityPerformRaise),     accessibilityPerformRaise);

            addMethod (@selector (isAccessibilitySelectorAllowed:), getIsAccessibilitySelectorAllowed);

           #if defined (MAC_OS_X_VERSION_10_13) && MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_13
            addMethod (@selector (accessibilityChildrenInNavigationOrder), getAccessibilityChildren);
           #endif

            registerClass();
        }

        //==============================================================================
        static bool isSelectable (AccessibleState state) noexcept
        {
            return state.isSelectable() || state.isMultiSelectable();
        }

        static NSArray* getSelectedChildren (NSArray* children)
        {
            NSMutableArray* selected = [[NSMutableArray new] autorelease];

            for (id child in children)
            {
                if (auto* handler = getHandler (child))
                {
                    const auto currentState = handler->getCurrentState();

                    if (isSelectable (currentState) && currentState.isSelected())
                        [selected addObject: child];
                }
            }

            return selected;
        }

        static void setSelectedChildren (NSArray* children, NSArray* selected)
        {
            for (id child in children)
            {
                if (auto* handler = getHandler (child))
                {
                    const auto currentState = handler->getCurrentState();
                    const BOOL isSelected = [selected containsObject: child];

                    if (isSelectable (currentState))
                    {
                        if (currentState.isSelected() != isSelected)
                            handler->getActions().invoke (AccessibilityActionType::toggle);
                    }
                    else if (currentState.isFocusable())
                    {
                        [child setAccessibilityFocused: isSelected];
                    }
                }
            }
        }

        //==============================================================================
        static BOOL getAccessibilityNotifiesWhenDestroyed (id, SEL)  { return YES; }

        static BOOL getIsAccessibilityEnabled (id self, SEL)
        {
            if (auto* handler = getHandler (self))
                return handler->getComponent().isEnabled();

            return NO;
        }

        static id getAccessibilityWindow (id self, SEL)
        {
            return [[self accessibilityParent] accessibilityWindow];
        }

        static id getAccessibilityFocusedUIElement (id self, SEL)
        {
            if (auto* handler = getHandler (self))
            {
                if (auto* modal = Component::getCurrentlyModalComponent())
                {
                    const auto& component = handler->getComponent();

                    if (! component.isParentOf (modal)
                         && component.isCurrentlyBlockedByAnotherModalComponent())
                    {
                        if (auto* modalHandler = modal->getAccessibilityHandler())
                        {
                            if (auto* focusChild = modalHandler->getChildFocus())
                                return (id) focusChild->getNativeImplementation();

                            return (id) modalHandler->getNativeImplementation();
                        }
                    }
                }

                if (auto* focusChild = handler->getChildFocus())
                    return (id) focusChild->getNativeImplementation();
            }

            return nil;
        }

        static id accessibilityHitTest (id self, SEL, NSPoint point)
        {
            if (auto* handler = getHandler (self))
            {
                if (auto* child = handler->getChildAt (roundToIntPoint (flippedScreenPoint (point))))
                    return (id) child->getNativeImplementation();

                return self;
            }

            return nil;
        }

        static id getAccessibilityParent (id self, SEL)
        {
            if (auto* handler = getHandler (self))
            {
                if (auto* parentHandler = handler->getParent())
                    return NSAccessibilityUnignoredAncestor ((id) parentHandler->getNativeImplementation());

                return NSAccessibilityUnignoredAncestor ((id) handler->getComponent().getWindowHandle());
            }

            return nil;
        }

        static NSArray* getAccessibilityChildren (id self, SEL)
        {
            if (auto* handler = getHandler (self))
            {
                auto children = handler->getChildren();

                auto* accessibleChildren = [NSMutableArray arrayWithCapacity: (NSUInteger) children.size()];

                for (auto* childHandler : children)
                    [accessibleChildren addObject: (id) childHandler->getNativeImplementation()];

                return accessibleChildren;
            }

            return nil;
        }

        static id getAccessibilityValue (id self, SEL)
        {
            if (auto* handler = getHandler (self))
            {
                if (handler->getCurrentState().isCheckable())
                    return juceStringToNS (handler->getCurrentState().isChecked() ? TRANS ("On") : TRANS ("Off"));

                return getAccessibilityValueFromInterfaces (*handler);
            }

            return nil;
        }

        static NSArray* getAccessibilitySelectedChildren (id self, SEL)
        {
            return getSelectedChildren ([self accessibilityChildren]);
        }

        static void setAccessibilitySelectedChildren (id self, SEL, NSArray* selected)
        {
            setSelectedChildren ([self accessibilityChildren], selected);
        }

        static NSAccessibilityOrientation getAccessibilityOrientation (id self, SEL)
        {
            if (auto* handler = getHandler (self))
                return handler->getComponent().getBounds().toFloat().getAspectRatio() > 1.0f
                           ? NSAccessibilityOrientationHorizontal
                           : NSAccessibilityOrientationVertical;

            return NSAccessibilityOrientationUnknown;
        }

        static BOOL getIsAccessibilityFocused (id self, SEL)
        {
            return [[self accessibilityWindow] accessibilityFocusedUIElement] == self;
        }

        static void setAccessibilityFocused (id self, SEL, BOOL focused)
        {
            if (auto* handler = getHandler (self))
            {
                if (focused)
                {
                    const WeakReference<Component> safeComponent (&handler->getComponent());

                    performActionIfSupported (self, AccessibilityActionType::focus);

                    if (safeComponent != nullptr)
                        handler->grabFocus();
                }
                else
                {
                    handler->giveAwayFocus();
                }
            }
        }

        static NSRect getAccessibilityFrame (id self, SEL)
        {
            if (auto* handler = getHandler (self))
                return flippedScreenRect (makeNSRect (handler->getComponent().getScreenBounds()));

            return NSZeroRect;
        }

        static NSAccessibilityRole getAccessibilityRole (id self, SEL)
        {
            if (auto* handler = getHandler (self))
            {
                switch (handler->getRole())
                {
                    case AccessibilityRole::popupMenu:
                    case AccessibilityRole::tooltip:
                    case AccessibilityRole::splashScreen:
                    case AccessibilityRole::dialogWindow:
                    case AccessibilityRole::window:        return NSAccessibilityWindowRole;

                    case AccessibilityRole::tableHeader:
                    case AccessibilityRole::unspecified:
                    case AccessibilityRole::group:         return NSAccessibilityGroupRole;

                    case AccessibilityRole::label:
                    case AccessibilityRole::staticText:    return NSAccessibilityStaticTextRole;

                    case AccessibilityRole::tree:
                    case AccessibilityRole::list:          return NSAccessibilityOutlineRole;

                    case AccessibilityRole::listItem:
                    case AccessibilityRole::treeItem:      return NSAccessibilityRowRole;

                    case AccessibilityRole::button:        return NSAccessibilityButtonRole;
                    case AccessibilityRole::toggleButton:  return NSAccessibilityCheckBoxRole;
                    case AccessibilityRole::radioButton:   return NSAccessibilityRadioButtonRole;
                    case AccessibilityRole::comboBox:      return NSAccessibilityPopUpButtonRole;
                    case AccessibilityRole::image:         return NSAccessibilityImageRole;
                    case AccessibilityRole::slider:        return NSAccessibilitySliderRole;
                    case AccessibilityRole::editableText:  return NSAccessibilityTextAreaRole;
                    case AccessibilityRole::menuItem:      return NSAccessibilityMenuItemRole;
                    case AccessibilityRole::menuBar:       return NSAccessibilityMenuRole;
                    case AccessibilityRole::table:         return NSAccessibilityListRole;
                    case AccessibilityRole::column:        return NSAccessibilityColumnRole;
                    case AccessibilityRole::row:           return NSAccessibilityRowRole;
                    case AccessibilityRole::cell:          return NSAccessibilityCellRole;
                    case AccessibilityRole::hyperlink:     return NSAccessibilityLinkRole;
                    case AccessibilityRole::progressBar:   return NSAccessibilityProgressIndicatorRole;
                    case AccessibilityRole::scrollBar:     return NSAccessibilityScrollBarRole;

                    case AccessibilityRole::ignored:       break;
                }

                return NSAccessibilityUnknownRole;
            }

            return nil;
        }

        static NSAccessibilityRole getAccessibilitySubrole (id self, SEL)
        {
            if (auto* handler = getHandler (self))
            {
                if (auto* textInterface = getTextInterface (self))
                    if (textInterface->isDisplayingProtectedText())
                        return NSAccessibilitySecureTextFieldSubrole;

                const auto role = handler->getRole();

                if (role == AccessibilityRole::window)                                     return NSAccessibilityStandardWindowSubrole;
                if (role == AccessibilityRole::dialogWindow)                               return NSAccessibilityDialogSubrole;
                if (role == AccessibilityRole::tooltip
                    || role == AccessibilityRole::splashScreen)                            return NSAccessibilityFloatingWindowSubrole;
                if (role == AccessibilityRole::toggleButton)                               return NSAccessibilityToggleSubrole;
                if (role == AccessibilityRole::treeItem
                    || role == AccessibilityRole::listItem)                                return NSAccessibilityOutlineRowSubrole;
                if (role == AccessibilityRole::row && getCellInterface (self) != nullptr)  return NSAccessibilityTableRowSubrole;

                const auto& component = handler->getComponent();

                if (auto* documentWindow = component.findParentComponentOfClass<DocumentWindow>())
                {
                    if (role == AccessibilityRole::button)
                    {
                        if (&component == documentWindow->getCloseButton())     return NSAccessibilityCloseButtonSubrole;
                        if (&component == documentWindow->getMinimiseButton())  return NSAccessibilityMinimizeButtonSubrole;
                        if (&component == documentWindow->getMaximiseButton())  return NSAccessibilityFullScreenButtonSubrole;
                    }
                }
            }

            return NSAccessibilityUnknownRole;
        }

        static NSString* getAccessibilityLabel (id self, SEL)
        {
            if (auto* handler = getHandler (self))
                return juceStringToNS (handler->getDescription());

            return nil;
        }

        //==============================================================================
        static NSInteger getAccessibilityInsertionPointLineNumber (id self, SEL)
        {
            if (auto* textInterface = getTextInterface (self))
                return [self accessibilityLineForIndex: textInterface->getTextInsertionOffset()];

            return 0;
        }

        static NSRange getAccessibilityVisibleCharacterRange (id self, SEL)
        {
            if (auto* textInterface = getTextInterface (self))
                return juceRangeToNS ({ 0, textInterface->getTotalNumCharacters() });

            return NSMakeRange (0, 0);
        }

        static NSInteger getAccessibilityNumberOfCharacters (id self, SEL)
        {
            if (auto* textInterface = getTextInterface (self))
                return textInterface->getTotalNumCharacters();

            return 0;
        }

        static NSString* getAccessibilitySelectedText (id self, SEL)
        {
            if (auto* textInterface = getTextInterface (self))
                return juceStringToNS (textInterface->getText (textInterface->getSelection()));

            return nil;
        }

        static NSRange getAccessibilitySelectedTextRange (id self, SEL)
        {
            if (auto* textInterface = getTextInterface (self))
            {
                const auto currentSelection = textInterface->getSelection();

                if (currentSelection.isEmpty())
                    return NSMakeRange ((NSUInteger) textInterface->getTextInsertionOffset(), 0);

                return juceRangeToNS (currentSelection);
            }

            return NSMakeRange (0, 0);
        }

        static NSAttributedString* getAccessibilityAttributedStringForRange (id self, SEL, NSRange range)
        {
            NSString* string = [self accessibilityStringForRange: range];

            if (string != nil)
                return [[[NSAttributedString alloc] initWithString: string] autorelease];

            return nil;
        }

        static NSRange getAccessibilityRangeForLine (id self, SEL, NSInteger line)
        {
            if (auto* textInterface = getTextInterface (self))
            {
                auto text = textInterface->getText ({ 0, textInterface->getTotalNumCharacters() });
                auto lines = StringArray::fromLines (text);

                if (line < lines.size())
                {
                    auto lineText = lines[(int) line];
                    auto start = text.indexOf (lineText);

                    if (start >= 0)
                        return NSMakeRange ((NSUInteger) start, (NSUInteger) lineText.length());
                }
            }

            return NSMakeRange (0, 0);
        }

        static NSString* getAccessibilityStringForRange (id self, SEL, NSRange range)
        {
            if (auto* textInterface = getTextInterface (self))
                return juceStringToNS (textInterface->getText (nsRangeToJuce (range)));

            return nil;
        }

        static NSRange getAccessibilityRangeForPosition (id self, SEL, NSPoint position)
        {
            if (auto* handler = getHandler (self))
            {
                if (auto* textInterface = handler->getTextInterface())
                {
                    auto screenPoint = roundToIntPoint (flippedScreenPoint (position));

                    if (handler->getComponent().getScreenBounds().contains (screenPoint))
                    {
                        auto offset = textInterface->getOffsetAtPoint (screenPoint);

                        if (offset >= 0)
                            return NSMakeRange ((NSUInteger) offset, 1);
                    }
                }
            }

            return NSMakeRange (0, 0);
        }

        static NSRange getAccessibilityRangeForIndex (id self, SEL, NSInteger index)
        {
            if (auto* textInterface = getTextInterface (self))
                if (isPositiveAndBelow (index, textInterface->getTotalNumCharacters()))
                    return NSMakeRange ((NSUInteger) index, 1);

            return NSMakeRange (0, 0);
        }

        static NSRect getAccessibilityFrameForRange (id self, SEL, NSRange range)
        {
            if (auto* textInterface = getTextInterface (self))
                return flippedScreenRect (makeNSRect (textInterface->getTextBounds (nsRangeToJuce (range)).getBounds()));

            return NSZeroRect;
        }

        static NSInteger getAccessibilityLineForIndex (id self, SEL, NSInteger index)
        {
            if (auto* textInterface = getTextInterface (self))
            {
                auto text = textInterface->getText ({ 0, (int) index });

                if (! text.isEmpty())
                    return StringArray::fromLines (text).size() - 1;
            }

            return 0;
        }

        static void setAccessibilitySelectedTextRange (id self, SEL, NSRange selectedRange)
        {
            if (auto* textInterface = getTextInterface (self))
                textInterface->setSelection (nsRangeToJuce (selectedRange));
        }

        //==============================================================================
        static NSArray* getAccessibilityRows (id self, SEL)
        {
            NSMutableArray* rows = [[NSMutableArray new] autorelease];

            if (auto* tableInterface = getTableInterface (self))
            {
                for (int row = 0; row < tableInterface->getNumRows(); ++row)
                {
                    if (auto* handler = tableInterface->getCellHandler (row, 0))
                    {
                        [rows addObject: (id) handler->getNativeImplementation()];
                    }
                    else
                    {
                        [rows addObject: [NSAccessibilityElement accessibilityElementWithRole: NSAccessibilityRowRole
                                                                                         frame: NSZeroRect
                                                                                         label: @"Offscreen Row"
                                                                                        parent: self]];
                    }
                }
            }

            return rows;
        }

        static NSArray* getAccessibilitySelectedRows (id self, SEL)
        {
            return getSelectedChildren ([self accessibilityRows]);
        }

        static void setAccessibilitySelectedRows (id self, SEL, NSArray* selected)
        {
            setSelectedChildren ([self accessibilityRows], selected);
        }

        static NSArray* getAccessibilityColumns (id self, SEL)
        {
            NSMutableArray* columns = [[NSMutableArray new] autorelease];

            if (auto* tableInterface = getTableInterface (self))
            {
                for (int column = 0; column < tableInterface->getNumColumns(); ++column)
                {
                    if (auto* handler = tableInterface->getCellHandler (0, column))
                    {
                        [columns addObject: (id) handler->getNativeImplementation()];
                    }
                    else
                    {
                        [columns addObject: [NSAccessibilityElement accessibilityElementWithRole: NSAccessibilityColumnRole
                                                                                            frame: NSZeroRect
                                                                                            label: @"Offscreen Column"
                                                                                           parent: self]];
                    }
                }
            }

            return columns;
        }

        static NSArray* getAccessibilitySelectedColumns (id self, SEL)
        {
            return getSelectedChildren ([self accessibilityColumns]);
        }

        static void setAccessibilitySelectedColumns (id self, SEL, NSArray* selected)
        {
            setSelectedChildren ([self accessibilityColumns], selected);
        }

        //==============================================================================
        static NSInteger getAccessibilityIndex (id self, SEL)
        {
            if (auto* handler = getHandler (self))
            {
                if (auto* cellInterface = handler->getCellInterface())
                {
                    NSAccessibilityRole role = [self accessibilityRole];

                    if ([role isEqual: NSAccessibilityRowRole])
                        return cellInterface->getRowIndex();

                    if ([role isEqual: NSAccessibilityColumnRole])
                        return cellInterface->getColumnIndex();
                }
            }

            return 0;
        }

        static NSInteger getAccessibilityDisclosureLevel (id self, SEL)
        {
            if (auto* handler = getHandler (self))
                if (auto* cellInterface = handler->getCellInterface())
                    return cellInterface->getDisclosureLevel();

            return 0;
        }

        static BOOL getIsAccessibilityExpanded (id self, SEL)
        {
            if (auto* handler = getHandler (self))
                return handler->getCurrentState().isExpanded();

            return NO;
        }

        //==============================================================================
        static BOOL accessibilityPerformShowMenu (id self, SEL)  { return performActionIfSupported (self, AccessibilityActionType::showMenu); }
        static BOOL accessibilityPerformRaise (id self, SEL)     { [self setAccessibilityFocused: YES]; return YES; }

        static BOOL accessibilityPerformDelete (id self, SEL)
        {
            if (auto* handler = getHandler (self))
            {
                if (hasEditableText (*handler))
                {
                    handler->getTextInterface()->setText ({});
                    return YES;
                }

                if (auto* valueInterface = handler->getValueInterface())
                {
                    if (! valueInterface->isReadOnly())
                    {
                        valueInterface->setValue ({});
                        return YES;
                    }
                }
            }

            return NO;
        }

        //==============================================================================
        static BOOL getIsAccessibilitySelectorAllowed (id self, SEL, SEL selector)
        {
            if (auto* handler = getHandler (self))
            {
                const auto role = handler->getRole();
                const auto currentState = handler->getCurrentState();

                for (auto textSelector : { @selector (accessibilityInsertionPointLineNumber),
                                           @selector (accessibilityVisibleCharacterRange),
                                           @selector (accessibilityNumberOfCharacters),
                                           @selector (accessibilitySelectedText),
                                           @selector (accessibilitySelectedTextRange),
                                           @selector (accessibilityAttributedStringForRange:),
                                           @selector (accessibilityRangeForLine:),
                                           @selector (accessibilityStringForRange:),
                                           @selector (accessibilityRangeForPosition:),
                                           @selector (accessibilityRangeForIndex:),
                                           @selector (accessibilityFrameForRange:),
                                           @selector (accessibilityLineForIndex:),
                                           @selector (setAccessibilitySelectedTextRange:) })
                {
                    if (selector == textSelector)
                        return handler->getTextInterface() != nullptr;
                }

                for (auto tableSelector : { @selector (accessibilityRowCount),
                                            @selector (accessibilityRows),
                                            @selector (accessibilitySelectedRows),
                                            @selector (accessibilityColumnCount),
                                            @selector (accessibilityColumns),
                                            @selector (accessibilitySelectedColumns) })
                {
                    if (selector == tableSelector)
                        return handler->getTableInterface() != nullptr;
                }

                for (auto cellSelector : { @selector (accessibilityRowIndexRange),
                                           @selector (accessibilityColumnIndexRange),
                                           @selector (accessibilityIndex),
                                           @selector (accessibilityDisclosureLevel) })
                {
                    if (selector == cellSelector)
                        return handler->getCellInterface() != nullptr;
                }

                for (auto valueSelector : { @selector (accessibilityValue),
                                            @selector (setAccessibilityValue:),
                                            @selector (accessibilityPerformDelete),
                                            @selector (accessibilityPerformIncrement),
                                            @selector (accessibilityPerformDecrement) })
                {
                    if (selector != valueSelector)
                        continue;

                    auto* valueInterface = handler->getValueInterface();

                    if (selector == @selector (accessibilityValue))
                        return valueInterface != nullptr
                            || hasEditableText (*handler)
                            || currentState.isCheckable();

                    auto hasEditableValue = [valueInterface] { return valueInterface != nullptr && ! valueInterface->isReadOnly(); };

                    if (selector == @selector (setAccessibilityValue:)
                     || selector == @selector (accessibilityPerformDelete))
                        return hasEditableValue() || hasEditableText (*handler);

                    auto isRanged = [valueInterface] { return valueInterface != nullptr && valueInterface->getRange().isValid(); };

                    if (selector == @selector (accessibilityPerformIncrement)
                     || selector == @selector (accessibilityPerformDecrement))
                        return hasEditableValue() && isRanged();

                    return NO;
                }

                for (auto actionSelector : { @selector (accessibilityPerformPress),
                                             @selector (accessibilityPerformShowMenu),
                                             @selector (accessibilityPerformRaise),
                                             @selector (setAccessibilityFocused:) })
                {
                    if (selector != actionSelector)
                        continue;

                    if (selector == @selector (accessibilityPerformPress))
                        return (handler->getCurrentState().isCheckable() && handler->getActions().contains (AccessibilityActionType::toggle))
                                || handler->getActions().contains (AccessibilityActionType::press);

                    if (selector == @selector (accessibilityPerformShowMenu))
                        return handler->getActions().contains (AccessibilityActionType::showMenu);

                    if (selector == @selector (accessibilityPerformRaise))
                        return [[self accessibilityRole] isEqual: NSAccessibilityWindowRole];

                    if (selector == @selector (setAccessibilityFocused:))
                        return currentState.isFocusable();
                }

                if (selector == @selector (accessibilitySelectedChildren))
                    return role == AccessibilityRole::popupMenu;

                if (selector == @selector (accessibilityOrientation))
                    return role == AccessibilityRole::scrollBar;

                if (selector == @selector (isAccessibilityExpanded))
                    return currentState.isExpandable();

                return sendSuperclassMessage<BOOL> (self, @selector (isAccessibilitySelectorAllowed:), selector);
            }

            return NO;
        }

        //==============================================================================
        JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AccessibilityElement)
    };

    //==============================================================================
    API_AVAILABLE (macos (10.10))
    AccessibilityElement::Holder accessibilityElement;

    //==============================================================================
    JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (AccessibilityNativeImpl)
};

//==============================================================================
AccessibilityNativeHandle* AccessibilityHandler::getNativeImplementation() const
{
    if (@available (macOS 10.10, *))
        return (AccessibilityNativeHandle*) nativeImpl->getAccessibilityElement();

    return nullptr;
}

static bool areAnyAccessibilityClientsActive()
{
    const String voiceOverKeyString ("voiceOverOnOffKey");
    const String applicationIDString ("com.apple.universalaccess");

    CFUniquePtr<CFStringRef> cfKey (voiceOverKeyString.toCFString());
    CFUniquePtr<CFStringRef> cfID  (applicationIDString.toCFString());

    CFUniquePtr<CFPropertyListRef> value (CFPreferencesCopyAppValue (cfKey.get(), cfID.get()));

    if (value != nullptr)
        return CFBooleanGetValue ((CFBooleanRef) value.get());

    return false;
}

static void sendAccessibilityEvent (id accessibilityElement,
                                    NSAccessibilityNotificationName notification,
                                    NSDictionary* userInfo)
{
    jassert (notification != NSAccessibilityNotificationName{});

    NSAccessibilityPostNotificationWithUserInfo (accessibilityElement, notification, userInfo);
}

static void sendHandlerNotification (const AccessibilityHandler& handler,
                                     NSAccessibilityNotificationName notification)
{
    if (! areAnyAccessibilityClientsActive() || notification == NSAccessibilityNotificationName{})
        return;

    if (@available (macOS 10.9, *))
    {
        if (id accessibilityElement = (id) handler.getNativeImplementation())
        {
            sendAccessibilityEvent (accessibilityElement, notification,
                                    (notification == NSAccessibilityLayoutChangedNotification
                                         ? @{ NSAccessibilityUIElementsKey: @[ accessibilityElement ] }
                                         : nil));
        }
    }
}

static NSAccessibilityNotificationName layoutChangedNotification()
{
    if (@available (macOS 10.9, *))
        return NSAccessibilityLayoutChangedNotification;

    static NSString* layoutChangedString = @"AXLayoutChanged";
    return layoutChangedString;
}

void notifyAccessibilityEventInternal (const AccessibilityHandler& handler, InternalAccessibilityEvent eventType)
{
    auto notification = [eventType]
    {
        switch (eventType)
        {
            case InternalAccessibilityEvent::elementCreated:         return NSAccessibilityCreatedNotification;
            case InternalAccessibilityEvent::elementDestroyed:       return NSAccessibilityUIElementDestroyedNotification;
            case InternalAccessibilityEvent::elementMovedOrResized:  return layoutChangedNotification();
            case InternalAccessibilityEvent::focusChanged:           return NSAccessibilityFocusedUIElementChangedNotification;
            case InternalAccessibilityEvent::windowOpened:           return NSAccessibilityWindowCreatedNotification;
            case InternalAccessibilityEvent::windowClosed:           break;
        }

        return NSAccessibilityNotificationName{};
    }();

    sendHandlerNotification (handler, notification);
}

void AccessibilityHandler::notifyAccessibilityEvent (AccessibilityEvent eventType) const
{
    auto notification = [eventType]
    {
        switch (eventType)
        {
            case AccessibilityEvent::textSelectionChanged:  return NSAccessibilitySelectedTextChangedNotification;
            case AccessibilityEvent::rowSelectionChanged:   return NSAccessibilitySelectedRowsChangedNotification;

            case AccessibilityEvent::textChanged:
            case AccessibilityEvent::valueChanged:          return NSAccessibilityValueChangedNotification;
            case AccessibilityEvent::titleChanged:          return NSAccessibilityTitleChangedNotification;
            case AccessibilityEvent::structureChanged:      return layoutChangedNotification();
        }

        return NSAccessibilityNotificationName{};
    }();

    sendHandlerNotification (*this, notification);
}

void AccessibilityHandler::postAnnouncement (const String& announcementString, AnnouncementPriority priority)
{
    if (! areAnyAccessibilityClientsActive())
        return;

    if (@available (macOS 10.9, *))
    {
        auto nsPriority = [priority]
        {
            // The below doesn't get noticed by the @available check above
            JUCE_BEGIN_IGNORE_WARNINGS_GCC_LIKE ("-Wunguarded-availability")

            switch (priority)
            {
                case AnnouncementPriority::low:    return NSAccessibilityPriorityLow;
                case AnnouncementPriority::medium: return NSAccessibilityPriorityMedium;
                case AnnouncementPriority::high:   return NSAccessibilityPriorityHigh;
            }

            jassertfalse;
            return NSAccessibilityPriorityLow;

            JUCE_END_IGNORE_WARNINGS_GCC_LIKE
        }();

        sendAccessibilityEvent ((id) [NSApp mainWindow],
                                NSAccessibilityAnnouncementRequestedNotification,
                                @{ NSAccessibilityAnnouncementKey: juceStringToNS (announcementString),
                                   NSAccessibilityPriorityKey:     @(nsPriority) });
     }
}

} // namespace juce