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LibWeb: Generate shorthand initial values after their longhands

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When parsing shorthand values, we'd like to use
`property_initial_value()` to get their longhand property values,
instead of hard-coding them as we currently do. That involves
recursively calling that function while the `initial_values` map is
being initialized, which causes problems because the shorthands appear
alphabetically before their longhand components, so the longhands aren't
initialized yet!

The solution here is to perform 2 passes when generating the code,
outputting properties without "longhands" first, and the rest after.
This could potentially cause issues when shorthands have multiple
levels, in particular `border` -> `border-color` -> `border-left-color`.
But, we do not currently define a default value for `border`, and
`border-color` takes only a single value, so it's fine for now. :^)
This commit is contained in:
Sam Atkins 2021-09-17 16:53:43 +01:00 • committed by Andreas Kling
parent bb1cc99750
commit 6ea9edf84b
1 changed files with 28 additions and 5 deletions
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33
Meta/Lagom/Tools/CodeGenerators/LibWeb/Generate_CSS_PropertyID_cpp.cpp
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@ -164,11 +164,14 @@ RefPtr<StyleValue> property_initial_value(PropertyID property_id)
ParsingContext parsing_context;
)~~~");
properties.for_each_member([&](auto& name, auto& value) {
VERIFY(value.is_object());
// NOTE: Parsing a shorthand property requires that its longhands are already available here.
// So, we do this in two passes: First longhands, then shorthands.
// Probably we should build a dependency graph and then handle them in order, but this
// works for now! :^)
if (value.as_object().has("initial")) {
auto& initial_value = value.as_object().get("initial");
auto output_initial_value_code = [&](auto& name, auto& object) {
if (object.has("initial")) {
auto& initial_value = object.get("initial");
VERIFY(initial_value.is_string());
auto initial_value_string = initial_value.as_string();
@ -180,11 +183,31 @@ RefPtr<StyleValue> property_initial_value(PropertyID property_id)
initial_values.set(PropertyID::@name:titlecase@, parsed_value.release_nonnull());
)~~~");
}
};
properties.for_each_member([&](auto& name, auto& value) {
VERIFY(value.is_object());
if (value.as_object().has("longhands"))
return;
output_initial_value_code(name, value.as_object());
});
properties.for_each_member([&](auto& name, auto& value) {
VERIFY(value.is_object());
if (!value.as_object().has("longhands"))
return;
output_initial_value_code(name, value.as_object());
});
generator.append(R"~~~(
}
return initial_values.get(property_id).value_or(nullptr);
auto maybe_value = initial_values.get(property_id);
if (!maybe_value.has_value()) {
dbgln("No initial value found for '{}' property!", string_from_property_id(property_id));
return nullptr;
}
return maybe_value.value();
}
bool property_has_quirk(PropertyID property_id, Quirk quirk)