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Talk more about nsINamed
(Clarity. Was two different readings, now one.) |
Wmccloskey (talk | contribs) (Talk more about nsINamed) |
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A lot of existing Gecko code uses an nsIEventTarget to decide where to dispatch runnables. The DocGroup and TabGroup classes expose EventTargetFor(category) methods that return an event target. Using this event target is equivalent to calling Dispatch on the DocGroup or TabGroup. (The one difference is that no name is provided for the runnable.) {TabGroup,DocGroup}::EventTargetFor can be called on any thread. As a convenience, you can also use nsIDocument::EventTargetFor (also callable from any thread) or nsIGlobalObject::EventTargetFor (main thread only). | A lot of existing Gecko code uses an nsIEventTarget to decide where to dispatch runnables. The DocGroup and TabGroup classes expose EventTargetFor(category) methods that return an event target. Using this event target is equivalent to calling Dispatch on the DocGroup or TabGroup. (The one difference is that no name is provided for the runnable.) {TabGroup,DocGroup}::EventTargetFor can be called on any thread. As a convenience, you can also use nsIDocument::EventTargetFor (also callable from any thread) or nsIGlobalObject::EventTargetFor (main thread only). | ||
=== Runnable names === | |||
One disadvantage of using EventTargetFor is that any runnables dispatched this way are not given a name. However, there are other options for assigning a name to runnables. To have a name, a runnable needs to implement the GetName method of the nsINamed interface. mozilla::Runnable already does this. You can use the SetName method on an existing mozilla::Runnable to change its name. | |||
Usually, though, you'll be using EventTargetFor in cases where you don't have direct access to the runnable. Typically you'll be giving the event target to a sub-system that will dispatch multiple runnables. Timers, the IPC code, and workers are examples of this. In these cases it's best to modify the sub-system to set pass down an appropriate name for the runnable. The IPC code, for example, can set the runnable name to the name of the message being dispatched. | |||
=== Example === | === Example === | ||
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} | } | ||
When using EventTargetFor, please try to set the name of the runnable as well. For timers, the name of the timer runnable is derived from the name of the | When using EventTargetFor, please try to set the name of the runnable as well. For timers, the name of the timer runnable is derived from the name of the timer callback (if it implements nsINamed). XMLHttpRequestMainThread is itself the timer callback, so we just need to add a GetName method: | ||
nsresult | nsresult | ||