Implement custom 'pad' values for @counter-style

Bug: 687225
Change-Id: Id90bf61c99aabcd464d12f9f43e95ec9bf5d5eb4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2585676
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836847}

third_party/blink/renderer/core/css/counter_style.cc

@@ -12,6 +12,7 @@
 #include "third_party/blink/renderer/core/css/css_value_pair.h"
 #include "third_party/blink/renderer/core/css/style_rule_counter_style.h"
 #include "third_party/blink/renderer/core/css_value_keywords.h"
+#include "third_party/blink/renderer/platform/text/text_break_iterator.h"
 #include "third_party/blink/renderer/platform/wtf/text/string_builder.h"
 
 namespace blink {
@@ -246,6 +247,12 @@ CounterStyle::CounterStyle(const StyleRuleCounterStyle& rule)
     }
   }
 
+  if (const CSSValue* pad = rule.GetPad()) {
+    const CSSValuePair& pair = To<CSSValuePair>(*pad);
+    pad_length_ = To<CSSPrimitiveValue>(pair.First()).GetIntValue();
+    pad_symbol_ = SymbolToString(pair.Second());
+  }
+
   // TODO(crbug.com/687225): Implement and populate other fields.
 }
 
@@ -269,6 +276,11 @@ void CounterStyle::ResolveExtends(const CounterStyle& extended) {
     negative_suffix_ = extended.negative_suffix_;
   }
 
+  if (!style_rule_->GetPad()) {
+    pad_length_ = extended.pad_length_;
+    pad_symbol_ = extended.pad_symbol_;
+  }
+
   // TODO(crbug.com/687225): Implement and populate other fields.
 }
 
@@ -324,23 +336,37 @@ bool CounterStyle::NeedsNegativeSign(int value) const {
   }
 }
 
-String CounterStyle::GenerateRepresentation(int value) const {
+String CounterStyle::GenerateFallbackRepresentation(int value) const {
   if (is_in_fallback_) {
     // We are in a fallback cycle. Use decimal instead.
     return GetDecimal().GenerateRepresentation(value);
   }
 
+  base::AutoReset<bool> in_fallback_scope(&is_in_fallback_, true);
+  return fallback_style_->GenerateRepresentation(value);
+}
+
+String CounterStyle::GenerateRepresentation(int value) const {
+  if (pad_length_ > kCounterLengthLimit)
+    return GenerateFallbackRepresentation(value);
+
   String initial_representation = GenerateInitialRepresentation(value);
-  if (initial_representation.IsNull()) {
-    base::AutoReset<bool> in_fallback_scope(&is_in_fallback_, true);
-    return fallback_style_->GenerateRepresentation(value);
-  }
+  if (initial_representation.IsNull())
+    return GenerateFallbackRepresentation(value);
 
-  // TODO(crbug.com/687225): Implement non-default 'pad' value.
+  wtf_size_t initial_length = NumGraphemeClusters(initial_representation);
+  if (NeedsNegativeSign(value)) {
+    initial_length += NumGraphemeClusters(negative_prefix_);
+    initial_length += NumGraphemeClusters(negative_suffix_);
+  }
+  wtf_size_t pad_copies =
+      pad_length_ > initial_length ? pad_length_ - initial_length : 0;
 
   StringBuilder result;
   if (NeedsNegativeSign(value))
     result.Append(negative_prefix_);
+  for (wtf_size_t i = 0; i < pad_copies; ++i)
+    result.Append(pad_symbol_);
   result.Append(initial_representation);
   if (NeedsNegativeSign(value))
     result.Append(negative_suffix_);

third_party/blink/renderer/core/css/counter_style.h

@@ -73,6 +73,10 @@ class CORE_EXPORT CounterStyle final : public GarbageCollected<CounterStyle> {
   // 'system', 'range' and 'symbols'/'additive-symbols' descriptor values.
   String GenerateInitialRepresentation(int value) const;
 
+  // Uses the fallback counter style to generate a representation for the value.
+  // It may recurse, and if it enters a loop, it uses 'decimal' instead.
+  String GenerateFallbackRepresentation(int value) const;
+
   // The corresponding style rule in CSS.
   Member<const StyleRuleCounterStyle> style_rule_;
 
@@ -100,6 +104,9 @@ class CORE_EXPORT CounterStyle final : public GarbageCollected<CounterStyle> {
   String negative_prefix_ = "-";
   String negative_suffix_;
 
+  String pad_symbol_;
+  wtf_size_t pad_length_ = 0;
+
   friend class CounterStyleMapTest;
 };
 

third_party/blink/renderer/core/css/counter_style_test.cc

@@ -206,4 +206,50 @@ TEST_F(CounterStyleTest, CustomNegative) {
   EXPECT_EQ("99", extended.GenerateRepresentation(99));
 }
 
+TEST_F(CounterStyleTest, CustomPad) {
+  InsertStyleElement(R"CSS(
+    @counter-style financial-decimal-pad {
+      system: extends decimal;
+      negative: '(' ')';
+      pad: 4 '0';
+    }
+
+    @counter-style extended {
+      system: extends financial-decimal-pad;
+    }
+  )CSS");
+  UpdateAllLifecyclePhasesForTest();
+
+  // Getting custom 'pad' directly from descriptor value.
+  const CounterStyle& financial_decimal_pad =
+      GetCounterStyle("financial-decimal-pad");
+  EXPECT_EQ("(99)", financial_decimal_pad.GenerateRepresentation(-99));
+  EXPECT_EQ("(01)", financial_decimal_pad.GenerateRepresentation(-1));
+  EXPECT_EQ("0000", financial_decimal_pad.GenerateRepresentation(0));
+  EXPECT_EQ("0001", financial_decimal_pad.GenerateRepresentation(1));
+  EXPECT_EQ("0099", financial_decimal_pad.GenerateRepresentation(99));
+
+  // Getting custom 'pad' indirectly by extending a counter style.
+  const CounterStyle& extended = GetCounterStyle("extended");
+  EXPECT_EQ("(99)", extended.GenerateRepresentation(-99));
+  EXPECT_EQ("(01)", extended.GenerateRepresentation(-1));
+  EXPECT_EQ("0000", extended.GenerateRepresentation(0));
+  EXPECT_EQ("0001", extended.GenerateRepresentation(1));
+  EXPECT_EQ("0099", extended.GenerateRepresentation(99));
+}
+
+TEST_F(CounterStyleTest, PadLengthLimit) {
+  InsertStyleElement(R"CSS(
+    @counter-style foo {
+      system: extends decimal;
+      pad: 1000 '0';
+    }
+  )CSS");
+  UpdateAllLifecyclePhasesForTest();
+
+  // Pad length is too long. Fallback to 'decimal'.
+  const CounterStyle& foo = GetCounterStyle("foo");
+  EXPECT_EQ("0", foo.GenerateRepresentation(0));
+}
+
 }  // namespace blink