Allow multiple TimingsCallbacks #43676
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This fixes flutter#39277
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| // TODO(liyuqian): once this is merged, modify the doc of | ||
| // [Window.onReportTimings] inside the engine repo to recommend using this | ||
| // API instead of using [Window.onReportTimings] directly. | ||
| _timingsCallbacksEnabled[callback] = true; |
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If I add the same callback twice it will only get called once? That's probably expected, but might be worth documenting?
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I've modified it to use a list so now it actually gets called twice. Documented such behavior too.
| assert(window.onReportTimings == null); | ||
| window.onReportTimings = (List<FrameTiming> timings) { | ||
| for (TimingsCallback callback in _timingsCallbacks) { | ||
| callback(timings); |
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What if callback removes itself from _timingsCallbacks? You probably want to iterate over a copy of _timingsCallbacks to avoid problems (_timingsCallbacks.toList() should work).
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The original map was for that. But I've changed it the the cloned list approach as you suggested. I was trying to save some copying time but I guess the saving isn't worth the confusion.
| /// Removes a callback that was earlier added by [addTimingsCallback]. | ||
| void removeTimingsCallback(TimingsCallback callback) { | ||
| assert(_timingsCallbacksEnabled.containsKey(callback)); | ||
| _timingsCallbacksEnabled[callback] = false; |
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Why do you keep track of whats enabled/disabled? Why not just remove it?
It also looks like this Map never gets cleaned up and the callback (and all the resources closured in to it) will be held in memory indefinitely. That seems like a leak?
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Changed to list and removed the calllback when needed.
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| void _executeTimingsCallbacks(List<FrameTiming> timings) { | ||
| final List<TimingsCallback> clonedCallbacks = | ||
| List<TimingsCallback>.from(_timingsCallbacks); |
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nit: either indent further or move to previous line.
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Thanks for catching this! I thought I indented by somehow it's missing...
| final List<TimingsCallback> clonedCallbacks = | ||
| List<TimingsCallback>.from(_timingsCallbacks); | ||
| for (TimingsCallback callback in clonedCallbacks) { | ||
| callback(timings); |
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In other places where we have similar code we check here if the callback is still in clonedCallbacks, for example:
flutter/packages/flutter/lib/src/foundation/change_notifier.dart
Lines 205 to 206 in b31ca1a
That way if your list is [callbackA, callbackB] and callbackA removes callbackB, callbackB is not called again. This would probably also make sense here?
Also from that link: Should we catch exceptions here that happen while executing callback?
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Done. Also added a test for the error handling.
| } | ||
| } | ||
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| final List<TimingsCallback> _timingsCallbacks = <TimingsCallback>[]; |
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nit: I would move this field up above addTimingsCallback, but that's probably up to personal taste.
This fixes flutter#39277 The following tests cover this change: - packages/flutter/test/foundation/service_extensions_test.dart - packages/flutter/test/scheduler/scheduler_test.dart
This fixes #39277
The following tests cover this change: