CSS Length calculation with MediaValues

Source/core/css/MediaQueryEvaluator.cpp

 /*
  * CSS Media Query Evaluator
  *
  * Copyright (C) 2006 Kimmo Kinnunen <kimmo.t.kinnunen@nokia.com>.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ skipping 313 matching lines @@
 static bool gridMediaFeatureEval(CSSValue* value, MediaFeaturePrefix op, const MediaValues&)
 {
     // if output device is bitmap, grid: 0 == true
     // assume we have bitmap device
     float number;
     if (value && numberValue(value, number))
         return compareValue(static_cast<int>(number), 0, op);
     return false;
 }
 
-static bool computeLengthWithoutStyle(CSSPrimitiveValue* primitiveValue, int defaultFontSize, int& result)
-{
-    // We're running in a background thread, so RenderStyle is not available.
-    // Nevertheless, we can evaluate length MQs with em, rem or px units.
-    // FIXME: Learn to support more units here, or teach CSSPrimitiveValue about MediaValues.
-    unsigned short type = primitiveValue->primitiveType();
-    int factor = 0;
-    if (type == CSSPrimitiveValue::CSS_EMS || type == CSSPrimitiveValue::CSS_REMS) {
-        if (defaultFontSize > 0)
-            factor = defaultFontSize;
-        else
-            return false;
-    } else if (type == CSSPrimitiveValue::CSS_PX) {
-        factor = 1;
-    } else {
-        return false;
-    }
-    result = roundForImpreciseConversion<int>(primitiveValue->getDoubleValue()*factor);
-    return true;
-}
-
-static bool computeLength(CSSValue* value, bool strict, RenderStyle* initialStyle, int defaultFontSize, int& result)
+static bool computeLength(CSSValue* value, const MediaValues& mediaValues, int& result)
 {
     if (!value->isPrimitiveValue())
         return false;
 
     CSSPrimitiveValue* primitiveValue = toCSSPrimitiveValue(value);
 
     if (primitiveValue->isNumber()) {
         result = primitiveValue->getIntValue();
-        return !strict || !result;
+        return !mediaValues.strictMode() || !result;
     }
 
     if (primitiveValue->isLength()) {
-        if (initialStyle) {
+        if (mediaValues.style()) {
             // Relative (like EM) and root relative (like REM) units are always resolved against
             // the initial values for media queries, hence the two initialStyle parameters.
             // FIXME: We need to plumb viewport unit support down to here.
-            result = primitiveValue->computeLength<int>(CSSToLengthConversionData(initialStyle, initialStyle, 0, 1.0 /* zoom */, true /* computingFontSize */));
+            result = primitiveValue->computeLength<int>(CSSToLengthConversionData(mediaValues.style(), mediaValues.style(), 0, 1.0 /* zoom */, true /* computingFontSize */));

[eseidel, 2014/04/08 16:51:28]

Any time we have to comment args like this we should be considering using a
struct for args instead.

FooArgs args;
args.mediaValues = mediaValues;
args.whatever = 0;
args.zoom = 1.0;
args.computingFontSize = true;

That makes the code much harder to get wrong. :)

Obviously not your "fault" here, but something we should consider if we're in
this code more.

         } else {
-            return computeLengthWithoutStyle(primitiveValue, defaultFontSize, result);
+            result = primitiveValue->computeLength<int>(CSSToLengthConversionData(&mediaValues, 1.0 /* zoom */, true /* computingFontSize */));
         }
         return true;
     }
 
     return false;
 }
 
 static bool deviceHeightMediaFeatureEval(CSSValue* value, MediaFeaturePrefix op, const MediaValues& mediaValues)
 {
     if (value) {
         int length;
-        return computeLength(value, mediaValues.strictMode(), mediaValues.style(), mediaValues.defaultFontSize(), length)
+        return computeLength(value, mediaValues, length)
             && compareValue(static_cast<int>(mediaValues.deviceHeight()), length, op);
     }
     // ({,min-,max-}device-height)
     // assume if we have a device, assume non-zero
     return true;
 }
 
 static bool deviceWidthMediaFeatureEval(CSSValue* value, MediaFeaturePrefix op, const MediaValues& mediaValues)
 {
     if (value) {
         int length;
-        return computeLength(value, mediaValues.strictMode(), mediaValues.style(), mediaValues.defaultFontSize(), length)
+        return computeLength(value, mediaValues, length)
             && compareValue(static_cast<int>(mediaValues.deviceWidth()), length, op);
     }
     // ({,min-,max-}device-width)
     // assume if we have a device, assume non-zero
     return true;
 }
 
 static bool heightMediaFeatureEval(CSSValue* value, MediaFeaturePrefix op, const MediaValues& mediaValues)
 {
     int height = mediaValues.viewportHeight();
     if (value) {
         int length;
-        return computeLength(value, mediaValues.strictMode(), mediaValues.style(), mediaValues.defaultFontSize(), length)
+        return computeLength(value, mediaValues, length)
             && compareValue(height, length, op);
     }
 
     return height;
 }
 
 static bool widthMediaFeatureEval(CSSValue* value, MediaFeaturePrefix op, const MediaValues& mediaValues)
 {
     int width = mediaValues.viewportWidth();
     if (value) {
         int length;
-        return computeLength(value, mediaValues.strictMode(), mediaValues.style(), mediaValues.defaultFontSize(), length)
+        return computeLength(value, mediaValues, length)
             && compareValue(width, length, op);
     }
 
     return width;
 }
 
 // Rest of the functions are trampolines which set the prefix according to the media feature expression used.
 
 static bool minColorMediaFeatureEval(CSSValue* value, MediaFeaturePrefix, const MediaValues& mediaValues)
 {
@@ skipping 241 matching lines @@
     // Call the media feature evaluation function. Assume no prefix and let
     // trampoline functions override the prefix if prefix is used.
     EvalFunc func = gFunctionMap->get(expr->mediaFeature().impl());
     if (func)
         return func(expr->value(), NoPrefix, *m_mediaValues);
 
     return false;
 }
 
 } // namespace