gecko-dev/layout/style/PreloadedStyleSheet.cpp

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4.5 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
// vim:cindent:tabstop=2:expandtab:shiftwidth=2:
/* 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, mGecko, mServo)
nsresult
PreloadedStyleSheet::GetSheet(StyleBackendType aType, StyleSheet** aResult)
{
*aResult = nullptr;
MOZ_DIAGNOSTIC_ASSERT(mLoaded);
RefPtr<StyleSheet>& sheet =
aType == StyleBackendType::Gecko ? mGecko : mServo;
if (!sheet) {
RefPtr<css::Loader> loader = new css::Loader(aType, nullptr);
nsresult rv = loader->LoadSheetSync(mURI, mParsingMode, true, &sheet);
NS_ENSURE_SUCCESS(rv, rv);
MOZ_ASSERT(sheet);
}
*aResult = sheet;
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.
auto type = nsLayoutUtils::StyloEnabled() ? StyleBackendType::Servo
: StyleBackendType::Gecko;
mLoaded = true;
StyleSheet* sheet;
return GetSheet(type, &sheet);
}
NS_IMPL_ISUPPORTS(PreloadedStyleSheet::StylesheetPreloadObserver,
nsICSSLoaderObserver)
NS_IMETHODIMP
PreloadedStyleSheet::StylesheetPreloadObserver::StyleSheetLoaded(
StyleSheet* aSheet, bool aWasAlternate, 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);
// As with the Preload() method, we can't be sure that the sheet will only be
// used with the backend that we're preloading it for now. If it's used with
// a different backend later, it will be synchronously loaded for that
// backend the first time it's used.
auto type = nsLayoutUtils::StyloEnabled() ? StyleBackendType::Servo
: StyleBackendType::Gecko;
RefPtr<StyleSheet>& sheet =
type == StyleBackendType::Gecko ? mGecko : mServo;
RefPtr<css::Loader> loader = new css::Loader(type, nullptr);
RefPtr<StylesheetPreloadObserver> obs =
new StylesheetPreloadObserver(aPromise, this);
return loader->LoadSheet(mURI, mParsingMode, false, obs, &sheet);
}
} // namespace mozilla