static bool evalResolution(CSSValue* value, Frame* frame, MediaFeaturePrefix op)
{
// According to MQ4, only 'screen', 'print' and 'speech' may match.
// FIXME: What should speech match? https://www.w3.org/Style/CSS/Tracker/issues/348
float actualResolution = 0;
// This checks the actual media type applied to the document, and we know
// this method only got called if this media type matches the one defined
// in the query. Thus, if if the document's media type is "print", the
// media type of the query will either be "print" or "all".
String mediaType = frame->view()->mediaType();
if (equalIgnoringCase(mediaType, "screen"))
actualResolution = clampTo<float>(frame->devicePixelRatio());
else if (equalIgnoringCase(mediaType, "print")) {
// The resolution of images while printing should not depend on the DPI
// of the screen. Until we support proper ways of querying this info
// we use 300px which is considered minimum for current printers.
actualResolution = 300 / cssPixelsPerInch;
}
if (!value)
return !!actualResolution;
if (!value->isPrimitiveValue())
return false;
CSSPrimitiveValue* resolution = toCSSPrimitiveValue(value);
if (resolution->isNumber())
return compareValue(actualResolution, resolution->getFloatValue(), op);
if (!resolution->isResolution())
return false;
if (resolution->isDotsPerCentimeter()) {
// To match DPCM to DPPX values, we limit to 2 decimal points.
// The http://dev.w3.org/csswg/css3-values/#absolute-lengths recommends
// "that the pixel unit refer to the whole number of device pixels that best
// approximates the reference pixel". With that in mind, allowing 2 decimal
// point precision seems appropriate.
return compareValue(
floorf(0.5 + 100 * actualResolution) / 100,
floorf(0.5 + 100 * resolution->getFloatValue(CSSPrimitiveValue::CSS_DPPX)) / 100, op);
}
return compareValue(actualResolution, resolution->getFloatValue(CSSPrimitiveValue::CSS_DPPX), op);
}
