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Investigation: timers synchronization #33

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Investigation: timers synchronization #33

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d5de41e
refactor(_DTXTimerTrampoline): Simplify [_DTXTimerTrampoline fire:]
ball-hayden Apr 16, 2022
129ed8c
style(_DTXTimerTrampoline): Correct indentation
ball-hayden Apr 16, 2022
d3c2af4
doc(NSTimer+DTXSpy): What is going on?
ball-hayden Apr 16, 2022
2100b7b
fix(NSTimer+DTXSpy): Invalidate timers before untracking (and releasi…
ball-hayden Apr 16, 2022
b5677c7
fix(NSTimer+DTXSpy): Tidy dealloc tracking for NSTimers
ball-hayden Apr 16, 2022
716e2a7
refactor(DTXUISyncResource): Reenable IMPLICIT_RETAIN_SELF and fix is…
ball-hayden Apr 16, 2022
a4aa2d5
fix(_DTXTimerTrampoline): Correct removal of display link associated …
ball-hayden Apr 18, 2022
ef92890
refactor(_DTXTimerTrampoline): Remove unused _timerDescription var
ball-hayden Apr 18, 2022
8b9d012
fix(DTXTimerTrampoline): HACK: Only fire timer callback if timer is d…
ball-hayden Apr 18, 2022
ee5c6a0
fixup! fix(_DTXTimerTrampoline): Correct removal of display link asso…
ball-hayden Apr 18, 2022
f2b47c5
fix(DTXTimerTrampoline): HACK: throw if no implementation for selector
ball-hayden Apr 18, 2022
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2 changes: 1 addition & 1 deletion DetoxSync/DetoxSync/Spies/NSTimer+DTXSpy.m
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Original file line number Diff line number Diff line change
Expand Up @@ -52,7 +52,7 @@ static void _DTXCFTimerTrampoline(CFRunLoopTimerRef timer, void *info)
// NSLog(@"❤️ %p", timer);

id<DTXTimerProxy> tp = [DTXTimerSyncResource existingTimerProxyWithTimer:NS(timer)];
[tp fire:(__bridge NSTimer*)timer];
[tp fire];
}

static CFRunLoopTimerRef (*__orig_CFRunLoopTimerCreate)(CFAllocatorRef allocator, CFAbsoluteTime fireDate, CFTimeInterval interval, CFOptionFlags flags, CFIndex order, CFRunLoopTimerCallBack callout, CFRunLoopTimerContext *context);
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2 changes: 1 addition & 1 deletion DetoxSync/DetoxSync/SyncResources/DTXTimerSyncResource.h
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Expand Up @@ -22,7 +22,7 @@ NS_ASSUME_NONNULL_BEGIN

//NSTimer
@property (nonatomic, weak) NSTimer* timer;
- (void)fire:(NSTimer*)timer;
- (void)fire;
@property (nonatomic) CFRunLoopRef runLoop;

//CADisplayLink
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49 changes: 13 additions & 36 deletions DetoxSync/DetoxSync/Utils/_DTXTimerTrampoline.m
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Expand Up @@ -112,47 +112,24 @@ - (void)setDisplayLink:(CADisplayLink*)displayLink
#endif
}

- (void)fire:(id)timer
- (void)fire
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The following changes are a bit more involved.

Firstly, there's no need for the timer parameter - we already have a reference to that as an ivar.

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I can understand why the timer argument is redundant.

{
//This is to ensure the timer is still valid after fire.
CFRunLoopRef runloop = CFRunLoopGetCurrent();
CFRunLoopMode mode = CFRunLoopCopyCurrentMode(runloop);
CFRunLoopPerformBlock(runloop, mode, ^{
if(CFRunLoopTimerIsValid((__bridge CFRunLoopTimerRef)timer) == NO)
{
[self untrack];

CFRelease(mode);

return;
}

CFRunLoopPerformBlock(runloop, mode, ^{
if(CFRunLoopTimerIsValid((__bridge CFRunLoopTimerRef)timer) == NO)
{
[self untrack];

CFRelease(mode);

return;
}

CFRelease(mode);
});
});
Comment on lines -117 to -142
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@ball-hayden ball-hayden Apr 16, 2022 •
edited
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If I understand right, the purpose of these are to see if the timer is still valid after it has fired.

If we ask if the timer is valid inline here, CFRunLoopTimerIsValid always evaluates to true, I assume because we're still within the fire function.

Here I'm proposing a different method.

We track the invalidation and removal of timers (in NSTimer+DTXSpy.m), which means we know when a repeating timer is stopping. We also know that a timer that doesn't repeat is finished once we have called its callback (or selector).

Therefore, we can simply call untrack if we are not a recurring timer after we have called its callback.

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As far as I understand, this code checks whether the timer needs to be untracked (for example, as you mentioned - in case of a non-repeating timer) immediately after finishing the fire.

Therefore, we can simply call untrack if we are not a recurring timer after we have called its callback.

Generally, this sounds right, but I'm not sure if recurring / non-recurring is our only flow. What about calling to CFRunLoopTimerInvalidate on the 3rd fire or something?

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Calling CFRunLoopTimerInvalidate will result in an explicit call to untrack from the spy:

https://github.com/PlayerData/DetoxSync/blob/f5cd8cbde60311bb8e41df7c773850cd73c8f84b/DetoxSync/DetoxSync/Spies/NSTimer%2BDTXSpy.m#L108


if(_callback)
{
CFRunLoopTimerContext ctx;
CFRunLoopTimerGetContext((__bridge CFRunLoopTimerRef)timer, &ctx);
_callback((__bridge CFRunLoopTimerRef)timer, ctx.info);
return;
CFRunLoopTimerGetContext((__bridge CFRunLoopTimerRef)_timer, &ctx);
_callback((__bridge CFRunLoopTimerRef)_timer, ctx.info);
}

if(_target && _sel) {
IMP impl = [_target methodForSelector:_sel];
void (*func)(id, SEL, NSTimer*) = (void *)impl;
func(_target, _sel, _timer);
}
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This is a small tidy-up recommended by https://stackoverflow.com/a/20058585

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👍


if(!_repeats) {
[self untrack];
}
Comment on lines +141 to 143
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I'm not sure if this will have the same result as the previous check.


#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
[_target performSelector:_sel withObject:timer];
#pragma clang diagnostic pop
Comment on lines -152 to -155
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why did you removed this? I guess it was there for a reason

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This is replaced by ln 131-138 - gaining a reference to impl explicitly is recommended.

I think my previous comment was lost - sorry.

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It wasn't, you're right #33 (comment), forgot about this for a moment 😅

}

- (void)track
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