Avalonia/native/Avalonia.Native/src/OSX/platformthreading.mm

#include "common.h"

class PlatformThreadingInterface;


class LoopCancellation : public ComSingleObject<IAvnLoopCancellation, &IID_IAvnLoopCancellation>
{
public:
    FORWARD_IUNKNOWN()
    
    bool Running = false;
    bool Cancelled = false;
    bool IsApp = false;

    virtual void Cancel() override
    {
        Cancelled = true;
        if(Running)
        {
            if(![NSThread isMainThread])
            {
                AddRef();
                dispatch_async(dispatch_get_main_queue(), ^{
                    if(Release() == 0)
                        return;
                    Cancel();
                });
                return;
            };

            Running = false;
            if(IsApp)
                [NSApp stop:nil];

            // Wakeup the event loop
            NSEvent* event = [NSEvent otherEventWithType:NSEventTypeApplicationDefined
                                                location:NSMakePoint(0, 0)
                                            modifierFlags:0
                                                timestamp:0
                                            windowNumber:0
                                                    context:nil
                                                    subtype:0
                                                    data1:0
                                                    data2:0];
            [NSApp postEvent:event atStart:YES];
        }
    };
};

// CFRunLoopTimerSetNextFireDate docs recommend to "create a repeating timer with an initial
// firing time in the distant future (or the initial firing time) and a very large repeat
// interval—on the order of decades or more"
static double distantFutureInterval = (double)50*365*24*3600;



@implementation ObserverStateHolder : NSObject
{
    @public bool InsideCallback;
}
@end

@implementation ObserverHolder : NSObject
{
    @public CFRunLoopObserverRef Observer;
    @public ObserverStateHolder* State;
}

- (ObserverHolder*) init
{
    self = [super init];
    self->State = [ObserverStateHolder new];
    return self;
}

- (void) dealloc
{
    if(Observer != nil)
    {
        CFRunLoopObserverInvalidate(Observer);
        CFRelease(Observer);
        Observer = nil;
    }
}

@end

@interface Signaler : NSObject
-(void) setEvents:(IAvnPlatformThreadingInterfaceEvents*) events;
-(void) updateTimer:(int)ms;
-(Signaler*) init;
-(void) destroyObserver;
-(void) signal;
@end

@implementation Signaler
{
    ComPtr<IAvnPlatformThreadingInterfaceEvents> _events;
    bool _wakeupDelegateSent;
    bool _signaled;
    bool _backgroundProcessingRequested;
    @public ObserverHolder* Observer;
    CFRunLoopTimerRef _timer;
}

- (void) checkSignaled
{
    bool signaled;
    @synchronized (self) {
        signaled = _signaled;
        _signaled = false;
    }
    if(signaled)
    {
        _events->Signaled();
    }
}

- (ObserverHolder*) createObserver
{
    ObserverHolder* holder = [ObserverHolder new];
    ObserverStateHolder* state = holder->State;
    
    holder->Observer = CFRunLoopObserverCreateWithHandler(nil,
                                                   kCFRunLoopBeforeSources
                                                   | kCFRunLoopAfterWaiting
                                                   | kCFRunLoopBeforeWaiting
                                                   ,
                                                   true, 0,
                                                   ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) {
        state->InsideCallback = true;
        if(activity == kCFRunLoopBeforeWaiting)
        {
            bool triggerProcessing;
            @synchronized (self) {
                triggerProcessing = self->_backgroundProcessingRequested;
                self->_backgroundProcessingRequested = false;
            }
            if(triggerProcessing)
                self->_events->ReadyForBackgroundProcessing();
        }
        [self checkSignaled];
        state->InsideCallback = false;
    });
    CFRunLoopAddObserver(CFRunLoopGetMain(), holder->Observer, kCFRunLoopCommonModes);
    return holder;
}

- (Signaler*) init
{
    Observer = [self createObserver];
    _timer = CFRunLoopTimerCreateWithHandler(nil, CFAbsoluteTimeGetCurrent() + distantFutureInterval, distantFutureInterval, 0, 0, ^(CFRunLoopTimerRef timer) {
        self->_events->Timer();
    });
    
    CFRunLoopAddTimer(CFRunLoopGetMain(), _timer, kCFRunLoopCommonModes);
    
    return self;
}

- (void) destroyObserver
{
    Observer = nil;
    
    if(_timer != nil)
    {
        CFRunLoopTimerInvalidate(_timer);
        CFRelease(_timer);
        _timer = nil;
    }
}

-(void) updateTimer:(int)ms
{
    if(_timer == nil)
        return;
    double interval = ms < 0 ? distantFutureInterval : ((double)ms / 1000);
    CFRunLoopTimerSetTolerance(_timer, 0);
    CFRunLoopTimerSetNextFireDate(_timer, CFAbsoluteTimeGetCurrent() + interval);
}

- (void) setEvents: (IAvnPlatformThreadingInterfaceEvents*) events
{
    _events = events;
}

- (void) signal
{
    @synchronized (self) {
        if(_signaled)
            return;
        _signaled = true;
        dispatch_async(dispatch_get_main_queue(), ^{
            [self checkSignaled];
        });
        CFRunLoopWakeUp(CFRunLoopGetMain());
    }
}

- (void) requestBackgroundProcessing
{
    @synchronized (self) {
        if(_backgroundProcessingRequested)
            return;
        _backgroundProcessingRequested = true;
        dispatch_async(dispatch_get_main_queue(), ^{
            // This is needed to wakeup the loop if we are called from inside of BeforeWait hook
        });
    }
    
        
}

@end


class PlatformThreadingInterface : public ComSingleObject<IAvnPlatformThreadingInterface, &IID_IAvnPlatformThreadingInterface>
{
private:
    ComPtr<IAvnPlatformThreadingInterfaceEvents> _events;
    Signaler* _signaler;
    ObserverHolder* _currentObserver;
public:
    FORWARD_IUNKNOWN()
    PlatformThreadingInterface()
    {
        _signaler = [Signaler new];
        _currentObserver = _signaler->Observer;
    };
    
    ~PlatformThreadingInterface()
    {
        [_signaler destroyObserver];
    }
    
    bool GetCurrentThreadIsLoopThread() override
    {
        return [NSThread isMainThread];
    };
    
    
    
    void SetEvents(IAvnPlatformThreadingInterfaceEvents *cb) override
    {
        _events = cb;
        [_signaler setEvents:cb];
    };
    
    IAvnLoopCancellation *CreateLoopCancellation() override
    {
        return new LoopCancellation();
    };
    
    void RunLoop(IAvnLoopCancellation *cancel) override
    {
        START_COM_CALL;
        auto can = dynamic_cast<LoopCancellation*>(cancel);
        if(can->Cancelled)
            return;
        can->Running = true;
        if(![NSApp isRunning])
        {
            can->IsApp = true;
            [NSApp run];
            return;
        }
        else
        {
            @autoreleasepool {
                auto previousObserver = _currentObserver;
                if(_currentObserver->State->InsideCallback)
                    _currentObserver = [_signaler createObserver];
                
                while(!can->Cancelled)
                {
                    @autoreleasepool
                    {
                        NSEvent* ev = [NSApp
                                       nextEventMatchingMask:NSEventMaskAny
                                       untilDate: [NSDate dateWithTimeIntervalSinceNow:1]
                                       inMode:NSDefaultRunLoopMode
                                       dequeue:true];
                        if(ev != NULL)
                            [NSApp sendEvent:ev];
                    }
                }
                _currentObserver = previousObserver;
            }
        }
    };
    
    void Signal() override
    {
        [_signaler signal];
    };
    
    void UpdateTimer(int ms) override
    {
        [_signaler updateTimer:ms];
    };
    
    void RequestBackgroundProcessing() override {
        [_signaler requestBackgroundProcessing];
    }
    
    
};

extern IAvnPlatformThreadingInterface* CreatePlatformThreading()
{
    return new PlatformThreadingInterface();
}