CSSParser Color.parse() for unexpected CSS properties

Matthew Elliot matthew.james.elliot at gmail.com
Wed Apr 4 14:44:04 UTC 2018

Hi David, thanks for the quick response, the parser does seem to have
knowledge of the property and values as in the method ...

ParsedValueImpl valueFor(String property, Term root, CSSLexer lexer)
throws ParseException {}

it looks for particular properties for parsing... e.g.

} else if ("-fx-background-color".equals(prop)) {
    return parsePaintLayers(root);
} else if ("-fx-background-image".equals(prop)) {
    return parseURILayers(root);
} else if ("-fx-background-insets".equals(prop)) {
     return parseInsetsLayers(root);

... but fx-alignment and fx-shape for example aren't listed here and fall
into this strange catch all place I noted in my previous email.

My follow up questions would be:

1. Why does it hit this for standard css properties as defined for JavaFX
components(fx-alignment, fx-shape, etc) I.e.
(hbox, vbox have -fx-alignment)
2. Even if it is wanted to be extensible, isn't by default attempting to
parse a color where the property is not known and therefore triggering
exception throw / catch on the thread critical to UI perf a less than
optimal solution? Could it be changed to handle this more gracefully than
catch / ignore exceptions?

Is it worth raising a ticket for such a topic, would it ever be considered
for improvement.

Thanks again,

On 4 April 2018 at 16:20, David Grieve <david.grieve at oracle.com> wrote:

> The parser doesn't have any concept of what the property is or value it
> might have. This allows the addition of new properties (such as an user
> might add for their own CSS styles) without having to modify the parser to
> handle them.
> On 4/4/18 10:03 AM, Matthew Elliot wrote:
>> Hi all, (first post).
>> I was profiling our PROD JavaFX application recently I discovered
>> something
>> rather peculiar in the CSSParser. (jdk1.8.0_151)
>> I noticed several hundred IllegalArgumentExceptions on the
>> JavaApplicationThread where for various unrelated css properties the
>> CSSParser is trying to parse a color. While the exception is subsequently
>> caught and swallowed silently doing this hundred of times on this thread
>> is
>> rather ugly and caused *minor* delays in the application thread.
>> This happened for alignment, shape, and a few other properties where
>> no-lookup case was found and it ended on approx. line 900 of the CSSParser
>> in
>> colorValueOfString()
>> with a value like 'center'; clearly no color.
>> // if the property value is another property, then it needs to be looked
>> up.
>> boolean needsLookup = isIdent && properties.containsKey(text);
>> if (needsLookup || ((value = colorValueOfString(str)) == null )) {
>>      // If the value is a lookup, make sure to use the lower-case text
>> so it matches the property
>>      // in the Declaration. If the value is not a lookup, then use str
>> since the value might
>>      // be a string which could have some case sensitive meaning
>>      //
>>      // TODO: isIdent is needed here because of RT-38345. This
>> effectively undoes RT-38201
>>      value = new ParsedValueImpl<String,String>(needsLookup ? text :
>> str, null, isIdent || needsLookup);
>> }
>> I had a look in the bug tracker https://bugs.openjdk.java.net/ but didn't
>> find much in this regard so thought I would post in case it has come up
>> before.
>> I saw some of the css properties are from our application and some from
>> e(fx)clipse which I can raise to Tom Schindl separately if it is a
>> stylesheet issue, however it would appear that for example -fx-alignment
>> in
>> a layout VBOX/HBOX component should be valid according to JavaFX docs.
>> More generally, is it expected that a property such as -fx-alignment
>> should
>> fall into this else {} catch all case, and why does JavaFX try to parse a
>> Color by default?
>> -fx-alignment: center;
>> Any input much appreciated.
>> Regards,
>> Matt

More information about the openjfx-dev mailing list