[CSS Typed OM] Implement CSSUnit::to for fixed length types

third_party/WebKit/Source/core/css/cssom/CSSUnitValue.cpp

Index: third_party/WebKit/Source/core/css/cssom/CSSUnitValue.cpp
diff --git a/third_party/WebKit/Source/core/css/cssom/CSSUnitValue.cpp b/third_party/WebKit/Source/core/css/cssom/CSSUnitValue.cpp
index f6fe21abf3ca36728fc02bac027292f500861315..347c60a8db7488c2c4a7385f20f43fa31515be5b 100644
--- a/third_party/WebKit/Source/core/css/cssom/CSSUnitValue.cpp
+++ b/third_party/WebKit/Source/core/css/cssom/CSSUnitValue.cpp
@@ -5,6 +5,7 @@
 #include "core/css/cssom/CSSUnitValue.h"
 
 #include "bindings/core/v8/ExceptionState.h"
+#include "core/css/CSSHelper.h"
 #include "platform/wtf/MathExtras.h"
 
 namespace blink {
@@ -85,12 +86,124 @@ CSSUnitValue* CSSUnitValue::to(CSSPrimitiveValue::UnitType unit) const {
     return Create(value_, unit_);
 
   // TODO(meade): Implement other types.

[Bugs Nash, 2017/06/28 23:50:27]

how many more types need to be implemented? is it feasible to include in this
todo the remaining types?

[meade_UTC10, 2017/06/29 06:44:09]

Done.

+  if (CSSPrimitiveValue::IsLength(unit_) && CSSPrimitiveValue::IsLength(unit)) {
+    // Only some kinds of lengths can be converted

[Bugs Nash, 2017/06/28 23:50:27]

perhaps 'relative types of lengths cannot be converted' is clearer?

[meade_UTC10, 2017/06/29 06:44:09]

Done.

+    if (CSSPrimitiveValue::IsRelativeUnit(unit_) ||
+        CSSPrimitiveValue::IsRelativeUnit(unit))
+      return nullptr;
+    return Create(ConvertFixedLength(unit), unit);
+  }
   if (CSSPrimitiveValue::IsAngle(unit_) && CSSPrimitiveValue::IsAngle(unit))
     return Create(ConvertAngle(unit), unit);
 
   return nullptr;
 }
 
+double CSSUnitValue::ConvertFixedLength(
+    CSSPrimitiveValue::UnitType unit) const {
+  switch (unit_) {
+    case CSSPrimitiveValue::UnitType::kPixels:
+      switch (unit) {
+        case CSSPrimitiveValue::UnitType::kCentimeters:
+          return value_ / kCssPixelsPerCentimeter;
+        case CSSPrimitiveValue::UnitType::kMillimeters:
+          return value_ / kCssPixelsPerMillimeter;
+        case CSSPrimitiveValue::UnitType::kInches:
+          return value_ / kCssPixelsPerInch;
+        case CSSPrimitiveValue::UnitType::kPoints:
+          return value_ / kCssPixelsPerPoint;
+        case CSSPrimitiveValue::UnitType::kPicas:
+          return value_ / kCssPixelsPerPica;
+        default:
+          NOTREACHED();
+          return 0;
+      }
+    case CSSPrimitiveValue::UnitType::kCentimeters:
+      switch (unit) {
+        case CSSPrimitiveValue::UnitType::kPixels:
+          return value_ * kCssPixelsPerCentimeter;
+        case CSSPrimitiveValue::UnitType::kMillimeters:
+          return value_ * 10;
+        case CSSPrimitiveValue::UnitType::kInches:
+          return value_ * (kCssPixelsPerCentimeter / kCssPixelsPerInch);

[Bugs Nash, 2017/06/28 23:50:27]

why do the pixels consts need to be used when converting between centimeters,
inches, points, or picas? they are all independent of pixels and could be
literal equations like the conversion from centimeters to millimeters right? if
you prefer using these named consts instead of literal equations i would suggest
being consistent and doing the same with the cm to mm conversions

[meade_UTC10, 2017/06/29 06:44:09]

It was a convenient way to do conversions without defining a large number of new
constants, and I think the less-well-known conversions (i.e. not =10) constants
need to be named. I defined a small number of new constants and made the
calculations with respect to those.

+        case CSSPrimitiveValue::UnitType::kPoints:
+          return value_ * (kCssPixelsPerCentimeter / kCssPixelsPerPoint);
+        case CSSPrimitiveValue::UnitType::kPicas:
+          return value_ * (kCssPixelsPerCentimeter / kCssPixelsPerPica);
+        default:
+          NOTREACHED();
+          return 0;
+      }
+    case CSSPrimitiveValue::UnitType::kMillimeters:
+      switch (unit) {
+        case CSSPrimitiveValue::UnitType::kPixels:
+          return value_ * kCssPixelsPerMillimeter;
+        case CSSPrimitiveValue::UnitType::kCentimeters:
+          return value_ / 10;
+        case CSSPrimitiveValue::UnitType::kInches:
+          return value_ * (kCssPixelsPerMillimeter / kCssPixelsPerInch);
+        case CSSPrimitiveValue::UnitType::kPoints:
+          return value_ * (kCssPixelsPerMillimeter / kCssPixelsPerPoint);
+        case CSSPrimitiveValue::UnitType::kPicas:
+          return value_ * (kCssPixelsPerMillimeter / kCssPixelsPerPica);
+        default:
+          NOTREACHED();
+          return 0;
+      }
+    case CSSPrimitiveValue::UnitType::kInches:
+      switch (unit) {
+        case CSSPrimitiveValue::UnitType::kPixels:
+          return value_ * kCssPixelsPerInch;
+        case CSSPrimitiveValue::UnitType::kMillimeters:
+          return value_ * (kCssPixelsPerInch / kCssPixelsPerMillimeter);
+        case CSSPrimitiveValue::UnitType::kCentimeters:
+          return value_ * (kCssPixelsPerInch / kCssPixelsPerCentimeter);
+        case CSSPrimitiveValue::UnitType::kPoints:
+          return value_ * (kCssPixelsPerInch / kCssPixelsPerPoint);
+        case CSSPrimitiveValue::UnitType::kPicas:
+          return value_ * (kCssPixelsPerInch / kCssPixelsPerPica);
+        default:
+          NOTREACHED();
+          return 0;
+      }
+    case CSSPrimitiveValue::UnitType::kPoints:
+      switch (unit) {
+        case CSSPrimitiveValue::UnitType::kPixels:
+          return value_ * kCssPixelsPerPoint;
+        case CSSPrimitiveValue::UnitType::kMillimeters:
+          return value_ * (kCssPixelsPerPoint / kCssPixelsPerMillimeter);
+        case CSSPrimitiveValue::UnitType::kCentimeters:
+          return value_ * (kCssPixelsPerPoint / kCssPixelsPerCentimeter);
+        case CSSPrimitiveValue::UnitType::kInches:
+          return value_ * (kCssPixelsPerPoint / kCssPixelsPerInch);
+        case CSSPrimitiveValue::UnitType::kPicas:
+          return value_ * (kCssPixelsPerPoint / kCssPixelsPerPica);
+        default:
+          NOTREACHED();
+          return 0;
+      }
+    case CSSPrimitiveValue::UnitType::kPicas:
+      switch (unit) {
+        case CSSPrimitiveValue::UnitType::kPixels:
+          return value_ * kCssPixelsPerPica;
+        case CSSPrimitiveValue::UnitType::kMillimeters:
+          return value_ * (kCssPixelsPerPica / kCssPixelsPerMillimeter);
+        case CSSPrimitiveValue::UnitType::kCentimeters:
+          return value_ * (kCssPixelsPerPica / kCssPixelsPerCentimeter);
+        case CSSPrimitiveValue::UnitType::kInches:
+          return value_ * (kCssPixelsPerPica / kCssPixelsPerInch);
+        case CSSPrimitiveValue::UnitType::kPoints:
+          return value_ * (kCssPixelsPerPica / kCssPixelsPerPoint);
+        default:
+          NOTREACHED();
+          return 0;
+      }
+    default:
+      NOTREACHED();
+      return 0;
+  }
+}
+
 double CSSUnitValue::ConvertAngle(CSSPrimitiveValue::UnitType unit) const {
   switch (unit_) {
     case CSSPrimitiveValue::UnitType::kDegrees: