[Specs] Remove all the obsolete specs.

sky/specs/runloop.md

Index: sky/specs/runloop.md
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-Sky's Run Loop
-==============
-
-Sky has three task queues, named idle, frame, and nextFrame.
-
-When a task is run, it has a time budget, and if the time budget is
-exceeded, then a catchable DeadlineExceededException exception is
-fired.
-
-```dart
-class DeadlineExceededException implements Exception { }
-```
-
-There is a method you can use that guards your code against these
-exceptions:
-
-```dart
-typedef void Callback();
-external guardAgainstDeadlineExceptions(Callback callback);
-// runs callback.
-// if the time budget for the _task_ expires while the callback is
-// running, the callback isn't interrupted, but the method will throw
-// an exception once the callback returns.
-```
-
-When Sky is to *process a task queue until a particular time*, with a
-queue *relevant task queue*, bits *filter bits*, a time
-*particular time*, and an *idle rule* which is either "sleep" or
-"abort", it must run the following steps:
-
-1. Let *remaining time* be the time until the given *particular time*.
-2. If *remaining time* is less than or equal to zero, exit this
-   algorithm.
-3. Let *task list* be the list of tasks in the *relevant task queue*
-   that have bits that, when 'and'ed with *filter bits*, are equal to
-   *filter bits*, whose required budget is less than or equal to
-   *remaining time*; and whose due time, if any, has been reached.
-4. If *task list* is empty, then if *idle rule* is "sleep" then return
-   to step 1, otherwise, exit this algorithm.
-5. Sort *task list* by the priority of each task, highest first.
-6. Remove the top task from *task list* from the *relevant task
-   queue*, and let that be *selected task*.
-7. Run *selected task*, with a budget of *remaining time* or 1ms,
-   whichever is shorter.
-8. Return to step 1.
-
-When Sky is to *drain a task queue for a specified time*, with a queue
-*relevant task queue*, bits *filter bits*, and a duration *budget*, it
-must run the following steps:
-
-2. Let *task list* be the list of tasks in the *relevant task queue*
-   that have bits that, when 'or'ed with *filter bits*, are non-zero;
-   and whose required budget is less than or equal to *budget*.
-4. If *task list* is empty, then exit.
-5. Sort *task list* by the priority of each task, highest first.
-6. Remove the top task from *task list* from the *relevant task
-   queue*, and let that be *selected task*.
-7. Run *selected task*, with a budget of *budget*.
-8. Decrease *budget* with the amount of time that *selected task* took
-   to run.
-9. If *selected task* threw an uncaught DeadlineExceededException
-   exception, then cancel all the tasks in *relevant task queue*.
-   Otherwise, return to step 2.
-
-Sky's run loop consists of running the following, at 120Hz (each loop
-takes 8.333ms):
-
-1. *Drain* the *frame task queue*, with bits
-   `application.frameTaskBits`, for 1ms.
-
-2. Create a task that does the following, then run it with a budget of
-   1ms:
-
-   1. Update the render tree, including calling childAdded(),
-      childRemoved(), and getLayoutManager() as needed, catching any
-      exceptions other than DeadlineExceededException exceptions.
-
-   If an exception is thrown by this, then the RenderNode tree will
-   continue to not quite match the element tree, which is fine.
-
-3. If there are no tasks on the *idle task queue* with bits
-   `LayoutKind`, create a task that tells the root node to layout if
-   it has needsLayout or descendantNeedsLayout, mark that with
-   priority 0 and bits `LayoutKind`, and add it to the *idle task
-   queue*.
-
-4. *Process* the *idle task queue*, with bits `LayoutKind`, with a
-   target time of t-1ms, where t is the time at which we have to send
-   the frame to the GPU, and with an *idle rule* of "abort".
-
-5. Create a task that does the following, then run it with a budget of
-   1ms:
-
-   1. If there are no RenderNodes that need paint, abort.
-
-   2. Call the `paint()` callback of the RenderNode that was least
-      recently marked as needing paint, catching any exceptions other
-      than DeadlineExceededException exceptions.
-
-   3. Jump to step 1.
-
-   If an exception is thrown by this, then some RenderNode objects
-      will be out-of-date during the paint.
-
-6. Send frame to GPU.
-
-7. Replace the frame queue with the nextFrame queue, and let the
-   nextFrame queue be an empty queue.
-
-8. *Process* the *idle task queue*, with bits
-   `application.idleTaskBits`, with a target time of t, where t is the
-   time at which we have to start the next frame's layout and paint
-   computations, and with an *idle rule* of "sleep".
-
-TODO(ianh): Update the timings above to have some relationship to
-reality.
-
-TODO(ianh): Define an API so that the application can adjust the
-budgets.
-
-Task kinds and priorities
--------------------------
-
-Tasks scheduled by futures get the priority and task kind bits from
-the task they are scheduled from.
-
-```dart
-int IdlePriority = 0; // tasks that can be delayed arbitrarily
-int FutureLayoutPriority = 1000; // async-layout tasks
-int AnimationPriority = 3000; // animation-related tasks
-int InputPriority = 4000; // input events
-int ScrollPriority = 5000; // framework-fired events for scrolling
-
-// possible idle queue task bits
-int IdleKind = 0x01; // tasks that should run during the idle loop
-int LayoutKind = 0x02; // tasks that should run during layout
-int TouchSafeKind = 0x04; // tasks that should keep running while there is a pointer down
-int idleTaskBits = IdleKind; // tasks must have all these bits to run during idle loop
-int layoutTaskBits = LayoutKind; // tasks must have all these bits to run during layout
-
-// possible frame queue task bits
-// (there are none at this time)
-int frameTaskBits = 0x00; // tasks must have all these bits to run during the frame loop
-```