Do not simplify calc(0px + 0%) into 0px

Currently, when we create |Length| from calc(), and then create a CSSPrimitiveValue from that |Length|, we may drop the percentage part if it's zero. As discussed at w3c/csswg-drafts#3482, zero percentages in calcs should be preserved. Hence, this part ensures that percentage is perserved in calc(0px + 0%) Note: we may want to preserve 0% in all cases, but that leads to many test failures, so we leave the investigation to future instead. This is also preparation for crrev.com/c/1777025, which switches the implementation of InterpolableLength to a math expression to support min/max. Bug: 991672 Change-Id: I386f42a323079cce3d6ee545fa00ef289406e8bf Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1779721 Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org> Reviewed-by: Emil A Eklund <eae@chromium.org> Cr-Commit-Position: refs/heads/master@{#693437}
chromium · Sep 4, 2019 · 80cac28 · 80cac28
1 parent 95a99b8
commit 80cac28
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diff --git a/third_party/blink/renderer/core/css/css_math_function_value.cc b/third_party/blink/renderer/core/css/css_math_function_value.cc
@@ -88,6 +88,8 @@ bool CSSMathFunctionValue::AccumulateLengthArray(CSSLengthArray& length_array,
 
 Length CSSMathFunctionValue::ConvertToLength(
     const CSSToLengthConversionData& conversion_data) const {
+  if (IsLength())
+    return Length::Fixed(ComputeLengthPx(conversion_data));
   return Length(ToCalcValue(conversion_data));
 }
 

diff --git a/third_party/blink/renderer/core/css/css_primitive_value.cc b/third_party/blink/renderer/core/css/css_primitive_value.cc
@@ -180,7 +180,7 @@ CSSPrimitiveValue* CSSPrimitiveValue::CreateFromLength(const Length& length,
       const CalculationValue& calc = length.GetCalculationValue();
       if (calc.IsExpression() || (calc.Pixels() && calc.Percent()))
         return CSSMathFunctionValue::Create(length, zoom);
-      if (calc.Percent()) {
+      if (!calc.Pixels()) {
         double num = calc.Percent();
         if (num < 0 && calc.IsNonNegative())
           num = 0;

diff --git a/third_party/blink/web_tests/external/wpt/css/css-values/calc-zero-percent-height.html b/third_party/blink/web_tests/external/wpt/css/css-values/calc-zero-percent-height.html
@@ -0,0 +1,30 @@
+<!doctype html>
+<link rel="help" href="https://www.w3.org/TR/css-values-4/#calc-computed-value">
+<link rel="help" href="https://www.w3.org/TR/CSS2/visudet.html#the-height-property">
+<link rel="author" title="Xiaocheng Hu" href="mailto:xiaochengh@chromium.org">
+<link rel="match" href="../reference/ref-filled-green-100px-square-only.html">
+<title>0% in calc() should be preserved</title>
+<script>
+CSS.registerProperty({
+  name: '--custom-height',
+  syntax: '<length-percentage>',
+  initialValue: 'calc(0% + 0px)',
+  inherits: false
+});
+</script>
+<style>
+.height-filler {
+  height: 100px;
+}
+
+.test {
+  width: 100px;
+  height: var(--custom-height);
+  background-color: green;
+}
+</style>
+<p>Test passes if there is a filled green square.</p>
+<div class="test">
+  <div class="height-filler">
+  </div>
+</div>