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# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this file,
# You can obtain one at
import argparse
import runpy
import string
import sys
# Generates a line of WebIDL with the given spelling of the property name
# (whether camelCase, _underscorePrefixed, etc.) and the given array of
# extended attributes.
def generateLine(propName, extendedAttrs):
return " [%s] attribute [LegacyNullToEmptyString] UTF8String %s;\n" % (
", ".join(extendedAttrs),
def generate(output, idlFilename, dataFile):
propsData = runpy.run_path(dataFile)["data"]
props = ""
for p in propsData.values():
# Skip properties which aren't valid in style rules.
if "Style" not in p.rules:
if p.type() == "alias":
if p.pref == propsData[p.prop_id].pref:
# We already added this as a BindingAlias for the original prop.
propId = p.prop_id
propId =
extendedAttrs = [
"BindingTemplate=(CSS2Property, eCSSProperty_%s)" % propId,
if p.pref != "":
assert "Internal" not in p.flags
# BackdropFilter is a special case where we want WebIDL to check
# a function instead of checking the pref directly.
if p.method == "BackdropFilter":
# MozTransform accessor is generated regardless, for compatibility,
# see bug 1861828, 1865332, 1860424, 1864970, 1865332, 1869119.
elif p.method not in ["MozTransform", "MozTransformOrigin"]:
extendedAttrs.append('Pref="%s"' % p.pref)
elif "EnabledInUASheetsAndChrome" in p.flags:
elif "Internal" in p.flags:
def add_extra_accessors(p):
prop = p.method
# webkit properties get a camelcase "webkitFoo" accessor
# as well as a capitalized "WebkitFoo" alias (added here).
if prop.startswith("Webkit"):
extendedAttrs.append('BindingAlias="%s"' % prop)
# Generate a name with camelCase spelling of property-name (or capitalized,
# for Moz-prefixed properties):
if not prop.startswith("Moz"):
prop = prop[0].lower() + prop[1:]
# Per spec, what's actually supposed to happen here is that we're supposed
# to have properties for:
# 1) Each supported CSS property name, camelCased.
# 2) Each supported name that contains or starts with dashes,
# without any changes to the name.
# 3) cssFloat
# Note that "float" will cause a property called "float" to exist due to (1)
# in that list.
# In practice, cssFloat is the only case in which "name" doesn't contain
# "-" but also doesn't match "prop". So the generateLine() call will
# cover (3) and all of (1) except "float". If we now add an alias
# for all the cases where "name" doesn't match "prop", that will cover
# "float" and (2).
if prop !=
extendedAttrs.append('BindingAlias="%s"' %
return prop
prop = add_extra_accessors(p)
if p.type() != "alias":
for a in p.aliases:
if p.pref == propsData[a].pref:
newProp = add_extra_accessors(propsData[a])
extendedAttrs.append('BindingAlias="%s"' % newProp)
props += generateLine(prop, extendedAttrs)
idlFile = open(idlFilename, "r")
idlTemplate =
+ string.Template(idlTemplate).substitute({"props": props})
+ "\n"
def main():
parser = argparse.ArgumentParser()
parser.add_argument("idlFilename", help="IDL property file template")
"preprocessorHeader", help="Header file to pass through the preprocessor"
args = parser.parse_args()
generate(sys.stdout, args.idlFilename, args.preprocessorHeader)
if __name__ == "__main__":