1280265 - Add an async version of nsIStyleSheetService.preloadSheet() API

Status: RESOLVED DUPLICATE of bug 1348442

(Core :: CSS Parsing and Computation, enhancement, P3)

Description

[Wladimir Palant]

Currently, nsIStyleSheetService.preloadSheet() method will load stylesheets synchronously. While this makes things somewhat easier, the requirement to retrieve the data synchronously is rather awkward with E10S.

Adblock Plus will soon use that API with a custom protocol scheme, to work around bug 1187099 among other things. However, the data is in the parent process so in order to implement nsIChannel.open() we'll have to message the parent process synchronously. This means that we'll block the entire content process whenever a new document is created - not a huge issue but still unnecessary.

IMHO, it should be possible to add nsIStyleSheetService.preloadSheet() which would do the same thing but load the stylesheet asynchronously and trigger a callback once the load is complete.

Comment 2

[Rob Wu [:robwu]]

The requested capability was implemented in bug 1348442.

Extensions automatically take advantage of the functionality when content_scripts in manifest.json (or other declarative content script APIs) are used.

Internal Firefox code can use nsIStyleSheetService's preloadSheetAsync and then windowUtils.addSheet with the result.

• preloadSheetAsync: https://searchfox.org/mozilla-central/rev/6f90f50b7a32cc062ab755e0653b3d3f512fe3bd/layout/base/nsIStyleSheetService.idl#57-63
• addSheet: https://searchfox.org/mozilla-central/rev/6f90f50b7a32cc062ab755e0653b3d3f512fe3bd/dom/interfaces/base/nsIDOMWindowUtils.idl#1869-1876