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LibWeb: Parse the CSS transform-origin property

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This is almost a PositionStyleValue, but it's serialized differently,
so let's use a StyleValueList with 2 length-percentage values.
This commit is contained in:
Simon Wanner 2022-03-21 19:11:06 +01:00 • committed by Andreas Kling
parent 1ad0e05ea1
commit 63055ff5ad
3 changed files with 136 additions and 0 deletions
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118
Userland/Libraries/LibWeb/CSS/Parser/Parser.cpp
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@ -3989,6 +3989,120 @@ RefPtr<StyleValue> Parser::parse_transform_value(Vector<StyleComponentValueRule>
return StyleValueList::create(move(transformations), StyleValueList::Separator::Space);
}
// https://www.w3.org/TR/css-transforms-1/#propdef-transform-origin
// FIXME: This only supports a 2D position
RefPtr<StyleValue> Parser::parse_transform_origin_value(Vector<StyleComponentValueRule> const& component_values)
{
enum class Axis {
None,
X,
Y,
};
struct AxisOffset {
Axis axis;
NonnullRefPtr<StyleValue> offset;
};
auto to_axis_offset = [](RefPtr<StyleValue> value) -> Optional<AxisOffset> {
if (value->is_percentage())
return AxisOffset { Axis::None, value->as_percentage() };
if (value->is_length())
return AxisOffset { Axis::None, value->as_length() };
if (value->has_length())
return AxisOffset { Axis::None, LengthStyleValue::create(value->to_length()) };
if (value->is_identifier()) {
switch (value->to_identifier()) {
case ValueID::Top:
return AxisOffset { Axis::Y, PercentageStyleValue::create(Percentage(0)) };
case ValueID::Left:
return AxisOffset { Axis::X, PercentageStyleValue::create(Percentage(0)) };
case ValueID::Center:
return AxisOffset { Axis::None, PercentageStyleValue::create(Percentage(50)) };
case ValueID::Bottom:
return AxisOffset { Axis::Y, PercentageStyleValue::create(Percentage(100)) };
case ValueID::Right:
return AxisOffset { Axis::X, PercentageStyleValue::create(Percentage(100)) };
default:
return {};
}
}
return {};
};
auto make_list = [](NonnullRefPtr<StyleValue> x_value, NonnullRefPtr<StyleValue> y_value) -> NonnullRefPtr<StyleValueList> {
NonnullRefPtrVector<StyleValue> values;
values.append(x_value);
values.append(y_value);
return StyleValueList::create(move(values), StyleValueList::Separator::Space);
};
switch (component_values.size()) {
case 1: {
auto single_value = to_axis_offset(parse_css_value(component_values[0]));
if (!single_value.has_value())
return nullptr;
// If only one value is specified, the second value is assumed to be center.
// FIXME: If one or two values are specified, the third value is assumed to be 0px.
switch (single_value->axis) {
case Axis::None:
case Axis::X:
return make_list(single_value->offset, PercentageStyleValue::create(Percentage(50)));
case Axis::Y:
return make_list(PercentageStyleValue::create(Percentage(50)), single_value->offset);
}
VERIFY_NOT_REACHED();
}
case 2: {
auto first_value = to_axis_offset(parse_css_value(component_values[0]));
auto second_value = to_axis_offset(parse_css_value(component_values[1]));
if (!first_value.has_value() || !second_value.has_value())
return nullptr;
RefPtr<StyleValue> x_value;
RefPtr<StyleValue> y_value;
if (first_value->axis == Axis::X) {
x_value = first_value->offset;
} else if (first_value->axis == Axis::Y) {
y_value = first_value->offset;
}
if (second_value->axis == Axis::X) {
if (x_value)
return nullptr;
x_value = second_value->offset;
// Put the other in Y since its axis can't have been X
y_value = first_value->offset;
} else if (second_value->axis == Axis::Y) {
if (y_value)
return nullptr;
y_value = second_value->offset;
// Put the other in X since its axis can't have been Y
x_value = first_value->offset;
} else {
if (x_value) {
VERIFY(!y_value);
y_value = second_value->offset;
} else {
VERIFY(!x_value);
x_value = second_value->offset;
}
}
// If two or more values are defined and either no value is a keyword, or the only used keyword is center,
// then the first value represents the horizontal position (or offset) and the second represents the vertical position (or offset).
// FIXME: A third value always represents the Z position (or offset) and must be of type <length>.
if (first_value->axis == Axis::None && second_value->axis == Axis::None) {
x_value = first_value->offset;
y_value = second_value->offset;
}
return make_list(x_value.release_nonnull(), y_value.release_nonnull());
}
}
return nullptr;
}
RefPtr<StyleValue> Parser::parse_as_css_value(PropertyID property_id)
{
auto component_values = parse_as_list_of_component_values();
@ -4136,6 +4250,10 @@ Result<NonnullRefPtr<StyleValue>, Parser::ParsingResult> Parser::parse_css_value
if (auto parsed_value = parse_transform_value(component_values))
return parsed_value.release_nonnull();
return ParsingResult::SyntaxError;
case PropertyID::TransformOrigin:
if (auto parse_value = parse_transform_origin_value(component_values))
return parse_value.release_nonnull();
return ParsingResult ::SyntaxError;
default:
break;
}