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serializeXML: Refactor the attribute ordering code

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Rewrite the code for ordering attributes in the output and extract it
into a function.  As a side-effect, we ensure we only use the
`.item(index)` method once per attribute because it is inefficient
(see https://bugs.python.org/issue40689).

Signed-off-by: Niels Thykier <niels@thykier.net>
This commit is contained in:
Niels Thykier 2020-05-21 12:15:32 +00:00
parent 5be6b03d7c
commit 9656569a72
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1 changed files with 38 additions and 24 deletions
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62
scour/scour.py
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@ -3433,6 +3433,42 @@ TEXT_CONTENT_ELEMENTS = ['text', 'tspan', 'tref', 'textPath', 'altGlyph',
'flowDiv', 'flowPara', 'flowSpan', 'flowTref', 'flowLine']
KNOWN_ATTRS = [
# TODO: Maybe update with full list from https://www.w3.org/TR/SVG/attindex.html
# (but should be kept intuitively ordered)
'id', 'xml:id', 'class',
'transform',
'x', 'y', 'z', 'width', 'height', 'x1', 'x2', 'y1', 'y2',
'dx', 'dy', 'rotate', 'startOffset', 'method', 'spacing',
'cx', 'cy', 'r', 'rx', 'ry', 'fx', 'fy',
'd', 'points',
] + sorted(svgAttributes) + [
'style',
]
KNOWN_ATTRS_ORDER_BY_NAME = defaultdict(lambda: len(KNOWN_ATTRS),
{name: order for order, name in enumerate(KNOWN_ATTRS)})
# use custom order for known attributes and alphabetical order for the rest
def _attribute_sort_key_function(attribute):
name = attribute.name
order_value = KNOWN_ATTRS_ORDER_BY_NAME[name]
return order_value, name
def attributes_ordered_for_output(element):
if not element.hasAttributes():
return []
attribute = element.attributes
# The .item(i) call is painfully slow (bpo#40689). Therefore we ensure we
# call it at most once per attribute.
# - it would be many times faster to use `attribute.values()` but sadly
# that is an "experimental" interface.
return sorted((attribute.item(i) for i in range(attribute.length)),
key=_attribute_sort_key_function)
# hand-rolled serialization function that has the following benefits:
# - pretty printing
# - somewhat judicious use of whitespace
@ -3453,30 +3489,8 @@ def serializeXML(element, options, indent_depth=0, preserveWhitespace=False):
outParts.extend([(indent_type * indent_depth), '<', element.nodeName])
# now serialize the other attributes
known_attr = [
# TODO: Maybe update with full list from https://www.w3.org/TR/SVG/attindex.html
# (but should be kept inuitively ordered)
'id', 'xml:id', 'class',
'transform',
'x', 'y', 'z', 'width', 'height', 'x1', 'x2', 'y1', 'y2',
'dx', 'dy', 'rotate', 'startOffset', 'method', 'spacing',
'cx', 'cy', 'r', 'rx', 'ry', 'fx', 'fy',
'd', 'points',
] + sorted(svgAttributes) + [
'style',
]
attrList = element.attributes
attrName2Index = dict([(attrList.item(i).nodeName, i) for i in range(attrList.length)])
# use custom order for known attributes and alphabetical order for the rest
attrIndices = []
for name in known_attr:
if name in attrName2Index:
attrIndices.append(attrName2Index[name])
del attrName2Index[name]
attrIndices += [attrName2Index[name] for name in sorted(attrName2Index)]
for index in attrIndices:
attr = attrList.item(index)
attrs = attributes_ordered_for_output(element)
for attr in attrs:
attrValue = attr.nodeValue
quote, xml_ent = choose_quote_character(attrValue)
attrValue = make_well_formed(attrValue, xml_ent)