gecko-dev/layout/style/PreloadedStyleSheet.cpp

114 строки
3.7 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* a CSS style sheet returned from nsIStyleSheetService.preloadSheet */
#include "PreloadedStyleSheet.h"
#include "mozilla/css/Loader.h"
#include "mozilla/dom/Promise.h"
#include "nsICSSLoaderObserver.h"
#include "nsLayoutUtils.h"
namespace mozilla {
PreloadedStyleSheet::PreloadedStyleSheet(nsIURI* aURI,
css::SheetParsingMode aParsingMode)
: mLoaded(false), mURI(aURI), mParsingMode(aParsingMode) {}
/* static */
nsresult PreloadedStyleSheet::Create(nsIURI* aURI,
css::SheetParsingMode aParsingMode,
PreloadedStyleSheet** aResult) {
*aResult = nullptr;
RefPtr<PreloadedStyleSheet> preloadedSheet =
new PreloadedStyleSheet(aURI, aParsingMode);
preloadedSheet.forget(aResult);
return NS_OK;
}
NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(PreloadedStyleSheet)
NS_INTERFACE_MAP_ENTRY(nsIPreloadedStyleSheet)
NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END
NS_IMPL_CYCLE_COLLECTING_ADDREF(PreloadedStyleSheet)
NS_IMPL_CYCLE_COLLECTING_RELEASE(PreloadedStyleSheet)
NS_IMPL_CYCLE_COLLECTION(PreloadedStyleSheet, mSheet)
nsresult PreloadedStyleSheet::GetSheet(StyleSheet** aResult) {
*aResult = nullptr;
MOZ_DIAGNOSTIC_ASSERT(mLoaded);
if (!mSheet) {
RefPtr<css::Loader> loader = new css::Loader;
nsresult rv = loader->LoadSheetSync(mURI, mParsingMode, true, &mSheet);
NS_ENSURE_SUCCESS(rv, rv);
MOZ_ASSERT(mSheet);
}
*aResult = mSheet;
return NS_OK;
}
nsresult PreloadedStyleSheet::Preload() {
MOZ_DIAGNOSTIC_ASSERT(!mLoaded);
// The nsIStyleSheetService.preloadSheet API doesn't tell us which backend
// the sheet will be used with, and it seems wasteful to eagerly create
// both a CSSStyleSheet and a ServoStyleSheet. So instead, we guess that
// the sheet type we will want matches the current value of the stylo pref,
// and preload a sheet of that type.
//
// If we guess wrong, we will re-load the sheet later with the requested type,
// and we won't really have front loaded the loading time as the name
// "preload" might suggest. Also, in theory we could get different data from
// fetching the URL again, but for the usage patterns of this API this is
// unlikely, and it doesn't seem worth trying to store the contents of the URL
// and duplicating a bunch of css::Loader's logic.
mLoaded = true;
StyleSheet* sheet;
return GetSheet(&sheet);
}
NS_IMPL_ISUPPORTS(PreloadedStyleSheet::StylesheetPreloadObserver,
nsICSSLoaderObserver)
NS_IMETHODIMP
PreloadedStyleSheet::StylesheetPreloadObserver::StyleSheetLoaded(
StyleSheet* aSheet, bool aWasDeferred, nsresult aStatus) {
MOZ_DIAGNOSTIC_ASSERT(!mPreloadedSheet->mLoaded);
mPreloadedSheet->mLoaded = true;
if (NS_FAILED(aStatus)) {
mPromise->MaybeReject(aStatus);
} else {
mPromise->MaybeResolve(mPreloadedSheet);
}
return NS_OK;
}
// Note: After calling this method, the preloaded sheet *must not* be used
// until the observer is notified that the sheet has finished loading.
nsresult PreloadedStyleSheet::PreloadAsync(NotNull<dom::Promise*> aPromise) {
MOZ_DIAGNOSTIC_ASSERT(!mLoaded);
RefPtr<css::Loader> loader = new css::Loader;
RefPtr<StylesheetPreloadObserver> obs =
new StylesheetPreloadObserver(aPromise, this);
return loader->LoadSheet(mURI, mParsingMode, false, obs, &mSheet);
}
} // namespace mozilla