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LibWeb: Add tokenization of calc expression

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Here the first step in understanding a calc() expression is taken:
Finding the start of an expression  and tokenizong it.
This commit is contained in:
Tobias Christiansen 2021-07-22 23:02:40 +02:00 • committed by Ali Mohammad Pur
parent f8bf6ae911
commit 7a4c8e0b76
Notes: sideshowbarker 2024-07-18 08:25:38 +09:00
1 changed files with 106 additions and 0 deletions
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106
Userland/Libraries/LibWeb/CSS/Parser/DeprecatedCSSParser.cpp
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@ -1,9 +1,11 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Tobias Christiansen <tobi@tobyase.de>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/GenericLexer.h>
#include <AK/HashMap.h>
#include <AK/SourceLocation.h>
#include <LibWeb/CSS/CSSImportRule.h>
@ -229,6 +231,104 @@ static StringView parse_custom_property_name(const StringView& value)
return value.substring_view(4, substring_length);
}
static StringView isolate_calc_expression(const StringView& value)
{
if (!value.starts_with("calc(") || !value.ends_with(")"))
return {};
auto substring_length = value.length() - 5 - 1;
return value.substring_view(5, substring_length);
}
static Optional<NonnullOwnPtr<CSS::CalculatedStyleValue::CalcSum>> parse_calc_expression(const StringView& expression_string)
{
// First, tokenize
struct CalcToken {
enum class Type {
Undefined,
Number,
Unit,
Whitespace,
Plus,
Minus,
Asterisk,
Slash,
OpenBracket,
CloseBracket,
} type { Type::Undefined };
String value {};
};
Vector<CalcToken> tokens;
GenericLexer lexer(expression_string);
while (!lexer.is_eof()) {
// Number
if (((lexer.next_is('+') || lexer.next_is('-')) && !isspace(lexer.peek(1)))
|| lexer.next_is('.')
|| lexer.next_is(isdigit)) {
auto number = lexer.consume_while(is_any_of("+-.0123456789"));
tokens.append(CalcToken { CalcToken::Type ::Number, number.to_string() });
continue;
}
auto ch = lexer.consume();
if (isspace(ch)) {
tokens.append(CalcToken { CalcToken::Type::Whitespace });
continue;
}
if (ch == '%') {
tokens.append(CalcToken { CalcToken::Type::Unit, "%" });
continue;
}
if (ch == '+') {
tokens.append(CalcToken { CalcToken::Type::Plus });
continue;
}
if (ch == '-') {
tokens.append(CalcToken { CalcToken::Type::Minus });
continue;
}
if (ch == '*') {
tokens.append(CalcToken { CalcToken::Type::Asterisk });
continue;
}
if (ch == '/') {
tokens.append(CalcToken { CalcToken::Type::Slash });
continue;
}
if (ch == '(') {
tokens.append(CalcToken { CalcToken::Type::OpenBracket });
continue;
}
if (ch == ')') {
tokens.append(CalcToken { CalcToken::Type::CloseBracket });
continue;
}
// Unit
if (isalpha(ch)) {
lexer.retreat();
auto unit = lexer.consume_while(isalpha);
tokens.append(CalcToken { CalcToken::Type::Unit, unit.to_string() });
continue;
}
VERIFY_NOT_REACHED();
}
return {};
}
RefPtr<CSS::StyleValue> parse_css_value(const CSS::DeprecatedParsingContext& context, const StringView& string, CSS::PropertyID property_id)
{
bool is_bad_length = false;
@ -257,6 +357,12 @@ RefPtr<CSS::StyleValue> parse_css_value(const CSS::DeprecatedParsingContext& con
return CSS::LengthStyleValue::create(CSS::Length::make_auto());
if (string.starts_with("var("))
return CSS::CustomStyleValue::create(parse_custom_property_name(string));
if (string.starts_with("calc(")) {
auto calc_expression_string = isolate_calc_expression(string);
auto calc_expression = parse_calc_expression(calc_expression_string);
if (calc_expression.has_value())
return CSS::CalculatedStyleValue::create(calc_expression_string, calc_expression.release_value());
}
auto value_id = CSS::value_id_from_string(string);
if (value_id != CSS::ValueID::Invalid)