Layout.reflow.async.duringDocLoad

From MozillaZine Knowledge Base

The title given to this article is incorrect due to technical limitations. The correct title is layout.reflow.async.duringDocLoad.

This article describes the preference layout.reflow.async.duringDocLoad. To add, delete, or modify this preference, you will need to edit your configuration — do not edit this article.

1 Background
2 Possible values and their effects
- 2.1 True
- 2.2 False
3 Caveats
4 First checked in
5 Has an effect in
6 Related bugs
7 Related preferences
8 External links

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Background

This preference affects the way a web page reflows (redraws itself) while loading.

When using synchronous reflow, Mozilla’s event loop blocks on all reflow events. In practical terms, this means that the UI can become inaccessible during the document load and some repaint events won’t fire. Asynchronous reflow solves this problem by limiting the maximum amount of time Gecko spends performing reflow events on each trip through the event loop and “posting” excess reflows to a queue to be processed on the next trip. This allows Mozilla’s event loop to proceed at a more predictable pace and keeps the UI responsive.

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Possible values and their effects

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True

Use asynchronous reflowing during document load. (Default)

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False

Use synchronous reflowing during document load.

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Caveats

This preference does not exist by default. If it is not present, the code uses asynchronous reflowing.
layout.reflow.timeslice must be a positive integer for this preference to work as designed.
Setting this preference to false can result in buggy behavior; for this reason, the preference was removed from the Mozilla 1.9 trunk (i.e., Firefox 3.0).

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