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Quantum/DOM: Difference between revisions
add SystemGroup explanation
Wmccloskey (talk | contribs) (small changes for language) |
Wmccloskey (talk | contribs) (add SystemGroup explanation) |
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To more precisely specify when one runnable can observe state from another runnable, we need to define some terminology. | To more precisely specify when one runnable can observe state from another runnable, we need to define some terminology. | ||
First, a TabGroup is the set of tabs that are related by window.opener. In a session with four tabs, where T1 opens T2 and T3 opens T4, the TabGroups are {T1, T2} and {T3, T4}. Once a tab joins a TabGroup, it never leaves it. TabGroups have the property that two tabs from different TabGroups can never observe each other's state. So a runnable from one TabGroup can run while a runnable from a different TabGroup is paused. | First, a <b>TabGroup</b> is the set of tabs that are related by window.opener. In a session with four tabs, where T1 opens T2 and T3 opens T4, the TabGroups are {T1, T2} and {T3, T4}. Once a tab joins a TabGroup, it never leaves it. TabGroups have the property that two tabs from different TabGroups can never observe each other's state. So a runnable from one TabGroup can run while a runnable from a different TabGroup is paused. | ||
A DocGroup is the collection of documents from a given TabGroup that share the same eTLD+1 part of their origins. So if a TabGroup contains tabs with documents {x.a.com, y.a.com, x.b.com, y.b.com}, then these documents will belong to two DocGroups: {x.a.com, y.a.com}, {x.b.com, y.b.com}. DocGroups are essentially a refinement of TabGroups to account for the fact that only same-origin documents can synchronously communicate. (The eTLD+1 part is to account for pages changing their origin by modifying document.domain.) So a runnable from one DocGroup can run while a runnable from a different DocGroup is paused. | A <b>DocGroup</b> is the collection of documents from a given TabGroup that share the same eTLD+1 part of their origins. So if a TabGroup contains tabs with documents {x.a.com, y.a.com, x.b.com, y.b.com}, then these documents will belong to two DocGroups: {x.a.com, y.a.com}, {x.b.com, y.b.com}. DocGroups are essentially a refinement of TabGroups to account for the fact that only same-origin documents can synchronously communicate. (The eTLD+1 part is to account for pages changing their origin by modifying document.domain.) So a runnable from one DocGroup can run while a runnable from a different DocGroup is paused. | ||
Given a document, you can find its DocGroup via nsIDocument::GetDocGroup. Given an inner or outer window, you can find its TabGroup and DocGroup via nsPIDOMWindow::{TabGroup,GetDocGroup}. These methods should only be called on the main thread. | Given a document, you can find its DocGroup via nsIDocument::GetDocGroup. Given an inner or outer window, you can find its TabGroup and DocGroup via nsPIDOMWindow::{TabGroup,GetDocGroup}. These methods should only be called on the main thread. | ||
A major task for the Quantum DOM project is to label runnables with DocGroups or | Runnables that do not affect web content can be labeled with the <b>SystemGroup</b>. Only use the system group if you know that the runnable will not run any content JS code or do any content DOM or layout access. | ||
A major task for the Quantum DOM project is to label runnables with DocGroups, TabGroups, or the SystemGroup. Using a DocGroup should be preferred over TabGroup since TabGroup is less specific. But for some runnables the best we can do is to give it a TabGroup. | |||
= Labeling = | = Labeling = | ||