[mathml] Add method to check whether operator should be stretched vertically

Add method to check whether operator should be stretched vertically [1] as well as a unit test. This method will be used in a follow-up CL.

[1] https://mathml-refresh.github.io/mathml-core/#stretchy-operator-axis

Bug: 6606
Change-Id: If57b13db6c8a710ff553ead6dff9157812122679
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2375346
Commit-Queue: Rob Buis <rbuis@igalia.com>
Reviewed-by: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801388}

third_party/blink/renderer/platform/text/character.cc

@@ -268,4 +268,28 @@ bool Character::HasDefiniteScript(UChar32 character) {
          hint_char_script != USCRIPT_COMMON;
 }
 
+// https://mathml-refresh.github.io/mathml-core/#stretchy-operator-axis
+static const UChar stretchy_operator_with_inline_axis[]{
+    0x003D, 0x005E, 0x005F, 0x007E, 0x00AF, 0x02C6, 0x02C7, 0x02C9, 0x02CD,
+    0x02DC, 0x02F7, 0x0302, 0x0332, 0x203E, 0x20D0, 0x20D1, 0x20D6, 0x20D7,
+    0x20E1, 0x2190, 0x2192, 0x2194, 0x2198, 0x2199, 0x219C, 0x219D, 0x219E,
+    0x21A0, 0x21A2, 0x21A3, 0x21A4, 0x21A6, 0x21A9, 0x21AA, 0x21AB, 0x21AC,
+    0x21AD, 0x21B4, 0x21B9, 0x21BC, 0x21BD, 0x21C0, 0x21C1, 0x21C4, 0x21C6,
+    0x21C7, 0x21C9, 0x21CB, 0x21CC, 0x21D0, 0x21D2, 0x21D4, 0x21DA, 0x21DB,
+    0x21DC, 0x21DD, 0x21E0, 0x21E2, 0x21E4, 0x21E5, 0x21E6, 0x21E8, 0x21F0,
+    0x21F6, 0x21FD, 0x21FE, 0x21FF, 0x23B4, 0x23B5, 0x23DC, 0x23DD, 0x23DE,
+    0x23DF, 0x23E0, 0x23E1, 0x2500, 0x27F5, 0x27F6, 0x27F7, 0x27F8, 0x27F9,
+    0x27FA, 0x27FB, 0x27FC, 0x27FD, 0x27FE, 0x27FF, 0x290C, 0x290D, 0x290E,
+    0x290F, 0x2910, 0x294E, 0x2950, 0x2952, 0x2953, 0x2956, 0x2957, 0x295A,
+    0x295B, 0x295E, 0x295F, 0x2B45, 0x2B46, 0xFE35, 0xFE36, 0xFE37, 0xFE38};
+
+bool Character::IsVerticalMathCharacter(UChar32 text_content) {
+  return text_content != kArabicMathematicalOperatorMeemWithHahWithTatweel &&
+         text_content != kArabicMathematicalOperatorHahWithDal &&
+         !std::binary_search(stretchy_operator_with_inline_axis,
+                             stretchy_operator_with_inline_axis +
+                                 base::size(stretchy_operator_with_inline_axis),
+                             text_content);
+}
+
 }  // namespace blink

third_party/blink/renderer/platform/text/character.h

@@ -202,6 +202,8 @@ class PLATFORM_EXPORT Character {
     return (c - (0x1C90 - 0x10D0));
   }
 
+  static bool IsVerticalMathCharacter(UChar32);
+
  private:
   static bool IsCJKIdeographOrSymbolSlow(UChar32);
   static bool IsHangulSlow(UChar32);

third_party/blink/renderer/platform/text/character_test.cc

@@ -411,4 +411,36 @@ TEST(CharacterTest, TransformedIsUprightInMixedVertical) {
   }
 }
 
+TEST(CharacterTest, IsVerticalMathCharacter) {
+  // https://mathml-refresh.github.io/mathml-core/#stretchy-operator-axis
+  const UChar stretchy_operator_with_inline_axis[]{
+      0x003D, 0x005E, 0x005F, 0x007E, 0x00AF, 0x02C6, 0x02C7, 0x02C9, 0x02CD,
+      0x02DC, 0x02F7, 0x0302, 0x0332, 0x203E, 0x20D0, 0x20D1, 0x20D6, 0x20D7,
+      0x20E1, 0x2190, 0x2192, 0x2194, 0x2198, 0x2199, 0x219C, 0x219D, 0x219E,
+      0x21A0, 0x21A2, 0x21A3, 0x21A4, 0x21A6, 0x21A9, 0x21AA, 0x21AB, 0x21AC,
+      0x21AD, 0x21B4, 0x21B9, 0x21BC, 0x21BD, 0x21C0, 0x21C1, 0x21C4, 0x21C6,
+      0x21C7, 0x21C9, 0x21CB, 0x21CC, 0x21D0, 0x21D2, 0x21D4, 0x21DA, 0x21DB,
+      0x21DC, 0x21DD, 0x21E0, 0x21E2, 0x21E4, 0x21E5, 0x21E6, 0x21E8, 0x21F0,
+      0x21F6, 0x21FD, 0x21FE, 0x21FF, 0x23B4, 0x23B5, 0x23DC, 0x23DD, 0x23DE,
+      0x23DF, 0x23E0, 0x23E1, 0x2500, 0x27F5, 0x27F6, 0x27F7, 0x27F8, 0x27F9,
+      0x27FA, 0x27FB, 0x27FC, 0x27FD, 0x27FE, 0x27FF, 0x290C, 0x290D, 0x290E,
+      0x290F, 0x2910, 0x294E, 0x2950, 0x2952, 0x2953, 0x2956, 0x2957, 0x295A,
+      0x295B, 0x295E, 0x295F, 0x2B45, 0x2B46, 0xFE35, 0xFE36, 0xFE37, 0xFE38};
+
+  for (UChar32 test_char = 0; test_char < kMaxCodepoint; test_char++) {
+    if (test_char == kArabicMathematicalOperatorMeemWithHahWithTatweel) {
+      EXPECT_FALSE(Character::IsVerticalMathCharacter(test_char));
+    } else if (test_char == kArabicMathematicalOperatorHahWithDal) {
+      EXPECT_FALSE(Character::IsVerticalMathCharacter(test_char));
+    } else {
+      bool in_vertical = !std::binary_search(
+          stretchy_operator_with_inline_axis,
+          stretchy_operator_with_inline_axis +
+              base::size(stretchy_operator_with_inline_axis),
+          test_char);
+      EXPECT_TRUE(Character::IsVerticalMathCharacter(test_char) == in_vertical);
+    }
+  }
+}
+
 }  // namespace blink

third_party/blink/renderer/platform/wtf/text/character_names.h

@@ -41,6 +41,8 @@ const UChar kActivateSymmetricSwappingCharacter = 0x206B;
 const UChar32 kAegeanWordSeparatorLineCharacter = 0x10100;
 const UChar32 kAegeanWordSeparatorDotCharacter = 0x10101;
 const UChar kArabicLetterMarkCharacter = 0x061C;
+const UChar32 kArabicMathematicalOperatorMeemWithHahWithTatweel = 0x1EEF0;
+const UChar32 kArabicMathematicalOperatorHahWithDal = 0x1EEF1;
 const UChar kBlackCircleCharacter = 0x25CF;
 const UChar kBlackSquareCharacter = 0x25A0;
 const UChar kBlackUpPointingTriangleCharacter = 0x25B2;
@@ -184,6 +186,8 @@ using WTF::unicode::kActivateSymmetricSwappingCharacter;
 using WTF::unicode::kAegeanWordSeparatorDotCharacter;
 using WTF::unicode::kAegeanWordSeparatorLineCharacter;
 using WTF::unicode::kArabicLetterMarkCharacter;
+using WTF::unicode::kArabicMathematicalOperatorHahWithDal;
+using WTF::unicode::kArabicMathematicalOperatorMeemWithHahWithTatweel;
 using WTF::unicode::kBlackCircleCharacter;
 using WTF::unicode::kBlackSquareCharacter;
 using WTF::unicode::kBlackUpPointingTriangleCharacter;