CSS Properties and Values API: Implement computation / computational independence

third_party/WebKit/Source/core/css/resolver/StyleBuilderConverter.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
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@@ skipping 1085 matching lines @@
 PassRefPtr<StylePath> StyleBuilderConverter::convertPathOrNone(StyleResolverState& state, const CSSValue& value)
 {
     if (value.isPathValue())
         return toCSSPathValue(value).stylePath();
     ASSERT(value.isPrimitiveValue() && toCSSPrimitiveValue(value).getValueID() == CSSValueNone);
     return nullptr;
 }
 
 const CSSValue& StyleBuilderConverter::convertRegisteredPropertyValue(const StyleResolverState& state, const CSSValue& value)
 {
-    // TODO(timloh): Resolve ems, etc.
+    // TODO(timloh): Images and transform-function values can also contain lengths.
+    if (value.isValueList()) {
+        CSSValueList* newList = CSSValueList::createSpaceSeparated();
+        for (const CSSValue* innerValue : toCSSValueList(value))
+            newList->append(convertRegisteredPropertyValue(state, *innerValue));
+        return *newList;
+    }
+
+    if (value.isPrimitiveValue()) {
+        const CSSPrimitiveValue& primitiveValue = toCSSPrimitiveValue(value);
+        if (primitiveValue.isCalculated() || CSSPrimitiveValue::isRelativeUnit(primitiveValue.typeWithCalcResolved())) {
+            Length length = primitiveValue.convertToLength(state.cssToLengthConversionData().copyWithAdjustedZoom(1));

[sashab, 2016/09/22 00:29:22]

I think we should really use the actual zoom here. If a user zooms in the page
their custom properties should change values, otherwise we'll get
inconsistencies and bugs.

Alternatively you could add a comment like:
// To not have any chance of values changing slightly due to rounding at
different zoom levels, ignore the zoom here.
But that just sounds like it's incorrect behavior, doesn't it?

[Timothy Loh, 2016/09/22 02:42:48]

I'm not sure what you're getting at here. If I specify left: 10px, I don't
expect it to end up as 20px. Similarly, if I specify --left: 10px, I also don't
expect it to end up as 20px.

[sashab, 2016/09/22 06:02:35]

Ok, add this comment then :)

[alancutter (OOO until 2018), 2016/09/22 07:58:41]

Agreed, at the very least add the comment.
I think any rounding errors here would be too negligible to worry about though.

[Timothy Loh, 2016/09/22 08:18:58]

Comment added. Probably negligible, but I prefer it this way. Since typed om
will return lengths as floats and not 6sf strings, maybe it matters more... I
dunno :/

+            return *CSSPrimitiveValue::create(length, 1);
+        }
+    }
     return value;
 }
 
 } // namespace blink