layout/style/ShadowParts.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "ShadowParts.h"
   8 #include "nsContentUtils.h"
   9 #include "nsString.h"
  10
  11 namespace mozilla {
  12
  13 static bool IsSpace(char16_t aChar) {
  14   return nsContentUtils::IsHTMLWhitespace(aChar);
  15 };
  16
  17 using SingleMapping = std::pair<RefPtr<nsAtom>, RefPtr<nsAtom>>;
  18
  19 // https://drafts.csswg.org/css-shadow-parts/#parsing-mapping
  20 //
  21 // Returns null on both tokens to signal an error.
  22 static SingleMapping ParseSingleMapping(const nsAString& aString) {
  23   const char16_t* c = aString.BeginReading();
  24   const char16_t* end = aString.EndReading();
  25
  26   const auto CollectASequenceOfSpaces = [&c, end]() {
  27     while (c != end && IsSpace(*c)) {
  28       ++c;
  29     }
  30   };
  31
  32   const auto CollectToken = [&c, end]() -> RefPtr<nsAtom> {
  33     const char16_t* t = c;
  34     while (c != end && !IsSpace(*c) && *c != ':') {
  35       ++c;
  36     }
  37     if (c == t) {
  38       return nullptr;
  39     }
  40     return NS_AtomizeMainThread(Substring(t, c));
  41   };
  42
  43   // Steps 1 and 2 are variable declarations.
  44   //
  45   // 3. Collect a sequence of code points that are space characters.
  46   CollectASequenceOfSpaces();
  47
  48   // 4. Collect a sequence of code points that are not space characters or
  49   // U+003A COLON characters, and call the result first token.
  50   RefPtr<nsAtom> firstToken = CollectToken();
  51
  52   // 5. If first token is empty then return error.
  53   if (!firstToken) {
  54     return {nullptr, nullptr};
  55   }
  56
  57   // 6. Collect a sequence of code points that are space characters.
  58   CollectASequenceOfSpaces();
  59
  60   // 7. If the end of the input has been reached, return the pair first
  61   // token/first token.
  62   if (c == end) {
  63     return {firstToken, firstToken};
  64   }
  65
  66   // 8. If character at position is not a U+003A COLON character, return error.
  67   if (*c != ':') {
  68     return {nullptr, nullptr};
  69   }
  70
  71   // 9. Consume the U+003A COLON character.
  72   ++c;
  73
  74   // 10. Collect a sequence of code points that are space characters.
  75   CollectASequenceOfSpaces();
  76
  77   // 11. Collect a sequence of code points that are not space characters or
  78   // U+003A COLON characters. and let second token be the result.
  79   RefPtr<nsAtom> secondToken = CollectToken();
  80
  81   // 12. If second token is empty then return error.
  82   if (!secondToken) {
  83     return {nullptr, nullptr};
  84   }
  85
  86   // 13. Collect a sequence of code points that are space characters.
  87   CollectASequenceOfSpaces();
  88
  89   // 14. If position is not past the end of input then return error.
  90   if (c != end) {
  91     return {nullptr, nullptr};
  92   }
  93
  94   // 15. Return the pair first token/second token.
  95   return {std::move(firstToken), std::move(secondToken)};
  96 }
  97
  98 // https://drafts.csswg.org/css-shadow-parts/#parsing-mapping-list
  99 ShadowParts ShadowParts::Parse(const nsAString& aString) {
 100   ShadowParts parts;
 101
 102   for (const auto& substring : aString.Split(',')) {
 103     auto mapping = ParseSingleMapping(substring);
 104     if (!mapping.first) {
 105       MOZ_ASSERT(!mapping.second);
 106       continue;
 107     }
 108     nsAtom* second = mapping.second.get();
 109     parts.mMappings.LookupForAdd(mapping.first)
 110         .OrInsert([] { return new PartList(); })
 111         ->AppendElement(std::move(mapping.second));
 112     parts.mReverseMappings.GetOrInsert(second) = std::move(mapping.first);
 113   }
 114
 115   return parts;
 116 }
 117
 118 #ifdef DEBUG
 119 void ShadowParts::Dump() const {
 120   if (mMappings.IsEmpty()) {
 121     printf("  (empty)\n");
 122     return;
 123   }
 124   for (auto& entry : mMappings) {
 125     nsAutoCString key;
 126     entry.GetKey()->ToUTF8String(key);
 127     printf("  %s: ", key.get());
 128
 129     bool first = true;
 130     for (nsAtom* part : *entry.GetData()) {
 131       if (!first) {
 132         printf(", ");
 133       }
 134       first = false;
 135       nsAutoCString value;
 136       part->ToUTF8String(value);
 137       printf("%s", value.get());
 138     }
 139     printf("\n");
 140   }
 141 }
 142 #endif
 143 }  // namespace mozilla