chromium/src/third_party/blink/renderer/core/css/media_feature_overrides.cc

// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "third_party/blink/renderer/core/css/media_feature_overrides.h"

#include "third_party/blink/renderer/core/css/parser/css_parser_context.h"
#include "third_party/blink/renderer/core/css/parser/css_parser_token_range.h"
#include "third_party/blink/renderer/core/css/parser/css_tokenizer.h"

namespace blink {

void MediaFeatureOverrides::SetOverride(const AtomicString& feature,
                                        const String& value_string) {
  CSSTokenizer tokenizer(value_string);
  const auto tokens = tokenizer.TokenizeToEOF();
  CSSParserTokenRange range(tokens);

  // TODO(xiaochengh): This is a fake CSSParserContext that only passes
  // down the CSSParserMode. Plumb the real CSSParserContext through, so that
  // web features can be counted correctly.
  const CSSParserContext* fake_context = MakeGarbageCollected<CSSParserContext>(
      kHTMLStandardMode, SecureContextMode::kInsecureContext);

  // MediaFeatureOverrides are used to emulate various media feature values.
  // These don't need to pass an ExecutionContext, since the parsing of
  // the actual CSS will determine whether or not the emulated values will come
  // into play (i.e. if you can parse an origin trial enabled feature, you
  // will never ask for the emulated override value).
  // Note that once a real CSSParserContext is plumbed through we can use its
  // Document to get the ExecutionContext so the extra parameter should be
  // removed.
  auto value =
      MediaQueryExp::Create(feature, range, *fake_context, nullptr).ExpValue();

  if (value.IsValid())
    overrides_.Set(feature, value);
  else
    overrides_.erase(feature);
}

}  // namespace blink