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Fix handling of negative numbers in list counters.

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Fixes #6818.
This commit is contained in:
Matt Brubeck 2015-08-04 14:48:39 -07:00
parent 86476804ca
commit 35ba731123
2 changed files with 30 additions and 10 deletions
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38
components/layout/generated_content.rs
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@ -522,37 +522,57 @@ pub fn static_representation(list_style_type: list_style_type::T) -> char {
/// Pushes the string that represents the value rendered using the given *alphabetic system* onto
/// the accumulator per CSS-COUNTER-STYLES § 3.1.4.
fn push_alphabetic_representation(mut value: i32, system: &[char], accumulator: &mut String) {
let mut abs_value = handle_negative_value(value, accumulator);
let mut string: SmallVec<[char; 8]> = SmallVec::new();
while value != 0 {
while abs_value != 0 {
// Step 1.
value = value - 1;
abs_value = abs_value - 1;
// Step 2.
string.push(system[(value as usize) % system.len()]);
string.push(system[abs_value % system.len()]);
// Step 3.
value = ((value as usize) / system.len()) as i32;
abs_value = abs_value / system.len();
}
accumulator.extend(string.iter().cloned().rev())
}
/// Pushes the string that represents the value rendered using the given *numeric system* onto the
/// accumulator per CSS-COUNTER-STYLES § 3.1.4.
/// accumulator per CSS-COUNTER-STYLES § 3.1.5.
fn push_numeric_representation(mut value: i32, system: &[char], accumulator: &mut String) {
let mut abs_value = handle_negative_value(value, accumulator);
// Step 1.
if value == 0 {
if abs_value == 0 {
accumulator.push(system[0]);
return
}
// Step 2.
let mut string: SmallVec<[char; 8]> = SmallVec::new();
while value != 0 {
while abs_value != 0 {
// Step 2.1.
string.push(system[(value as usize) % system.len()]);
string.push(system[abs_value % system.len()]);
// Step 2.2.
value = ((value as usize) / system.len()) as i32;
abs_value = abs_value / system.len();
}
// Step 3.
accumulator.extend(string.iter().cloned().rev())
}
/// If the system uses a negative sign, handle negative values per CSS-COUNTER-STYLES § 2.
///
/// Returns the absolute value of the counter.
fn handle_negative_value(value: i32, accumulator: &mut String) -> usize {
// 3. If the counter value is negative and the counter style uses a negative sign, instead
// generate an initial representation using the absolute value of the counter value.
if value < 0 {
// TODO: Support different negative signs using the 'negative' descriptor.
// https://drafts.csswg.org/date/2015-07-16/css-counter-styles/#counter-style-negative
accumulator.push('-');
value.abs() as usize
} else {
value as usize
}
}