CSS Custom Properties (Variables)

Source/core/css/resolver/CSSVariableResolver.cpp

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "core/css/resolver/CSSVariableResolver.h"
+
+#include "core/CSSPropertyNames.h"
+#include "core/CSSValueKeywords.h"
+#include "core/StyleBuilderFunctions.h"
+#include "core/css/CSSVariableData.h"
+#include "core/css/parser/CSSParserToken.h"
+#include "core/css/parser/CSSParserTokenRange.h"
+#include "core/css/parser/CSSParserValues.h"
+#include "core/css/parser/CSSPropertyParser.h"
+#include "wtf/Vector.h"
+
+namespace blink {
+
+enum ResolutionBehavior {
+    ResolvingVariableDefinitions,
+    DoNotResolveVariableDefinitions
+};
+
+static bool isVariableReferenceToken(CSSParserToken& token)
+{
+    return token.type() == FunctionToken && token.valueEqualsIgnoringCase("var");
+}
+
+// TODO(leviw): These will get moved out of StyleBuilder
+// TODO(leviw): Validation should no longer be required here
+static bool findEndOfVariableReference(Vector<CSSParserToken>& resolvedTokens, unsigned startOffset, unsigned& end, unsigned& commaLocation)
+{
+    end = 0;
+    commaLocation = 0;
+    unsigned bracketCount = 0;
+    bool validSyntax = true;
+    for (unsigned i = startOffset; i < resolvedTokens.size(); ++i) {
+        CSSParserTokenType type = resolvedTokens[i].type();
+
+        if (type == CommaToken && !commaLocation) {
+            commaLocation = i;
+        } else if (type == LeftParenthesisToken) {
+            bracketCount++;
+        } else if (type == RightParenthesisToken) {
+            if (bracketCount) {
+                bracketCount--;
+            } else {
+                end = i;
+                break;
+            }
+        } else if (type != WhitespaceToken && !commaLocation) {
+            // We need content after a comma for valid syntax, but if it occurs
+            // before a comma its invalid.
+            validSyntax = commaLocation;
+        }
+    }
+    if (!end || !validSyntax) {
+        end = resolvedTokens.size() - 1;
+        return false;
+    }
+    return true;
+}
+
+// TODO(leviw): Factor this into another file. Make it actually recursive.
+static unsigned resolveVariableTokensRecursive(Vector<CSSParserToken>& resolvedTokens, const StyleVariableData* styleVariableData, HashSet<AtomicString>& variablesSeen, unsigned startOffset, ResolutionBehavior resolutionBehavior)
+{
+    ASSERT(startOffset);
+    // There should be at least 2 tokens after the start position: a the variable name and the close bracket
+    if (resolvedTokens.size() < startOffset + 1)
+        return -1;
+
+    unsigned commaLocation, end;
+
+    // Find the variable location
+    unsigned variableLocation = 0;
+    for (unsigned i = startOffset; i < resolvedTokens.size(); ++i) {
+        if (resolvedTokens[i].type() == IdentToken) {
+            variableLocation = i;
+            break;
+        }
+        if (resolvedTokens[i].type() != WhitespaceToken) {
+            findEndOfVariableReference(resolvedTokens, i, end, commaLocation);
+            unsigned length = end - startOffset + 2;

[leviw_travelin_and_unemployed, 2015/06/20 00:58:15]

I need to go back and remove all these magic offsets.

+            resolvedTokens.remove(startOffset - 1, length);
+            return -1;
+        }
+    }
+
+    // Find default value and match braces
+    if (!findEndOfVariableReference(resolvedTokens, variableLocation + 1, end, commaLocation)) {
+        unsigned length = end - startOffset + 2;
+        resolvedTokens.remove(startOffset - 1, length);
+        return -1;
+    }
+    
+    unsigned length = end - startOffset + 2;
+    unsigned varFunctionPosition = startOffset - 1;
+
+    AtomicString variableName = resolvedTokens[variableLocation].value();
+
+    if (variablesSeen.contains(variableName)) {
+        // Cycle detected.
+        resolvedTokens.clear();
+        return 0;
+    }
+
+    CSSVariableData* variableData = styleVariableData ? styleVariableData->getVariable(variableName) : nullptr;
+    if (variableData) {
+        Vector<CSSParserToken>& tokens = variableData->tokens();
+        if (variableData->needsVariableResolution()) {
+            ASSERT(resolutionBehavior == ResolvingVariableDefinitions);
+            variablesSeen.add(variableName);
+            for (unsigned i = 0; i < tokens.size(); ++i) {
+                if (isVariableReferenceToken(tokens[i])) {
+                    i += resolveVariableTokensRecursive(tokens, styleVariableData, variablesSeen, i + 1, resolutionBehavior);
+                }
+            }
+            variablesSeen.remove(variableName);
+        }
+        if (tokens.size()) {
+            resolvedTokens.remove(startOffset - 1, length);
+            resolvedTokens.insert(startOffset - 1, tokens);
+            return tokens.size();
+        }
+    }
+
+    // Fallback on default value if present
+    if (!commaLocation) {
+        resolvedTokens.remove(varFunctionPosition, length);
+        return 0;
+    }
+
+    // Move the tokens to the beginning of the variable reference
+    unsigned defaultValueOffset = commaLocation + 1;
+    unsigned defaultValueLength = end - commaLocation - 1;
+    for (unsigned i = 0; i < defaultValueLength; ++i)
+        resolvedTokens[varFunctionPosition + i] = resolvedTokens[defaultValueOffset + i];
+    resolvedTokens.remove(varFunctionPosition + defaultValueLength, length - defaultValueLength);
+
+    return commaLocation;
+}
+
+static void resolveVariableReferencesFromTokens(Vector<CSSParserToken>& tokens, const StyleVariableData* variables, ResolutionBehavior resolutionBehavior)
+{
+    HashSet<AtomicString> variablesSeen;
+
+    for (unsigned i = 0; i < tokens.size(); ++i) {
+        if (isVariableReferenceToken(tokens[i])) {
+            unsigned validTokens = resolveVariableTokensRecursive(tokens, variables, variablesSeen, i + 1, resolutionBehavior);
+            if (validTokens < 1) {
+                tokens.clear();
+                break;
+            }
+            i += validTokens - 1;
+        }
+    }
+}
+
+void CSSVariableResolver::resolveAndApplyVariableReferences(StyleResolverState& state, CSSPropertyID id, CSSPrimitiveValue* value)
+{
+    // TODO(leviw): This should be a stack
+    Vector<CSSParserToken> tokens = value->getVariableDataValue()->tokens();
+
+    resolveVariableReferencesFromTokens(tokens, state.style()->variables(), DoNotResolveVariableDefinitions);
+
+    if (!tokens.size())
+        return;
+
+    CSSParserContext context(HTMLStandardMode, 0);
+
+    WillBeHeapVector<CSSProperty, 256> parsedProperties;
+
+    bool usesRemUnits, usesVariables;
+
+    CSSParserValueList valueList(CSSParserTokenRange(tokens, 0), usesRemUnits, usesVariables);
+
+    if (!valueList.size())
+        return;
+
+    CSSPropertyParser::parseValue(id, false, &valueList, context, parsedProperties, StyleRule::Type::Style);
+
+    unsigned parsedPropertiesCount = parsedProperties.size();
+    for (unsigned i = 0; i < parsedPropertiesCount; ++i)
+        StyleBuilder::applyProperty(parsedProperties[i].id(), state, parsedProperties[i].value());
+}
+
+void CSSVariableResolver::resolveVariableDefinitions(StyleResolverState& state)
+{
+    StyleVariableData* variables = state.style()->variables();
+    if (!variables)
+        return;
+
+    // TODO(leviw): Skip resolving definitions without references.
+    for (auto& variable : variables->m_data) {
+        if (!variable.value->needsVariableResolution())
+            continue;
+        Vector<CSSParserToken>& tokens = variable.value->tokens();
+
+        resolveVariableReferencesFromTokens(tokens, variables, ResolvingVariableDefinitions);
+
+        // TODO(leviw): This should have been done at parse-time and used the normal machinery.
+        // for (CSSParserToken& token : tokens) {
+        //     if (token.type() == IdentToken) {
+        //         if (token.valueEqualsIgnoringCase("initial")) {
+        //             tokens.clear();
+        //             break;
+        //         } else if (token.valueEqualsIgnoringCase("inherit")) {
+        //             if (state.parentStyle()->variables()) {
+        //                 if 
+        //             }
+        //             tokens = 
+        //             break;
+        //         }
+        //     }
+        // }
+
+        // TODO(leviw): this is a hack!
+        variable.value->setNeedsVariableResolution(false);
+
+        // CSSParserTokenRange range(resolvedTokens, &variable.value->scope());
+        // CSSVariableData* resolvedData = CSSVariableData::create(range).leakRef();
+        // resolvedData->setResolved();
+        // variable.value = resolvedData;
+
+        // // TODO(leviw): Can I do this!?
+        // variable.value->scope().m_tokens = resolvedTokens;
+        // variable.value->setResolved();
+
+    }
+}
+
+} // namespace blink