Greg,
There is already a standard programmatic API for parsing CSS stylesheets
with several Java implementations. See
http://www.w3.org/Style/CSS/SAC/
These parsers provide events like element selectors (which can map to
component types), class condition selectors (like .example, which can map
to the contents of "class" attributes) and ID condition selectors (like
#exampleId, which can map to values of "id" or "wtkx:id" attributes).
Is this hard to implement? The plus side is you get a very powerful, well
established styling language with room to grow as needed. It simplifies
the debate on implementation and requirements because we just pick which
parts of CSS we want to do. Pivot does not need to claim full CSS
support. We just need to document which parts it does. Adopting CSS also
makes learning Pivot styling easier for web devs and designers.
Cheers,
Michael
On Sat, 3 Jul 2010, Greg Brown wrote:
True, but it is also more complex than JSON, which so far has worked
well for us. JSON property names and value types map nicely to the Java
bean property names and values used by the skin classes. Also, we
already have a JSONSerializer - we'd have to write additional support
for CSS, and I'm not sure that is justified.
On Jul 2, 2010, at 9:51 PM, Michael Allman wrote:
It would be very premature for me to provide a good example. I've barely
started my first Pivot app. Also, I can say that this can't be done with Flex
apps either. So I never used it there. Doesn't mean it might not have come in
handy once or twice... I dunno. It may be practically useless. Although I
have seen it used many times in html.
This comes back to my earlier post. Why not support a subset of CSS syntax
itself? It's a very mature spec for styling declarative ui stuff.
Cheers,
Michael
On Fri, 2 Jul 2010, Greg Brown wrote:
I have been thinking about that and I have some ideas. But I would like to
understand how often that use case actually comes up. I know CSS supports it,
but in practice (in Pivot specifically) I wonder how important it is?
On Jul 2, 2010, at 7:30 PM, Michael Allman wrote:
Hi Greg,
How would one specify multiple named styles for a component element? Like
<PushButton styles="redButton bigFont"/>
Cheers,
Michael
On Fri, 2 Jul 2010, Greg Brown wrote:
Hi all,
I have been thinking about this and I think I have a fairly elegant solution that will also
significantly extend the capabilities of BXMLSerializer. I am thinking of extending the
<bxml:include> tag to support loading of arbitrary content. Currently, it only supports
includes of other BXML files, but there is no reason that it couldn't be modified to include
other types, such as JSON, XML, or even images. All we'd have to do is determine an appropriate
serializer to use for the include - this could be inferred based on file extension or could be
specified explicitly via a "mimeType" attribute to the include tag. The MIME
type-to-serializer mappings could be configurable such that an include could literally be used
to load any type of object.
One application of such an extension would be styling. <bxml:include> could be used to load a "stylesheet" - a JSON
file containing a "map of maps". The format of this file would be identical to the format I had been considering for the
"named styles" approach - each key/value pair in the file would essentially represent a "style class". For example,
the following JSON file would define a "redButton" class:
{ redButton: {
backgroundColor: "#aa0000",
color: "#ffffff"
}
}
In a BXML document, this file could be included as follows:
<bxml:include bxml:id="styles" src="styles.json"/>
The "redButton" style could then be applied to a button as follows:
<PushButton styles="$styles.redButton"/>
Unlike the previous solution I proposed, this approach would require no changes to
the Component or Container classes whatsoever. With the exception of extending the
<bxml:include> tag, it relies entirely on existing functionality (and existing
BXML syntax, so developers will already be familiar with it).
There are obviously other applications as well. Some simple examples:
<TableView>
<tableData>
<bxml:include src="table_data.json"/>
</tableData>
</TableView>
<TreeView>
<treeData>
<bxml:include src="tree_data.xml"/>
</treeData>
</TreeView>
One challenge might be how to specify the MIME/serializer mapping for an
include (we won't want BXMLSerializer to include all possible mappings by
default). This could be inherited from the parent serializer, but I think that
a BXML syntax for specifying it in markup is probably a good idea.
Anyway, I think this would be an extremely flexible and useful addition to the
serializer, and I think it also handles the styling case pretty well. Let me
know what you think.
G
On Jul 2, 2010, at 1:34 PM, Greg Brown wrote:
FYI, named styles are turning out to be a lot more challenging than I expected.
The solution I proposed the other day doesn't work - elements in BXML aren't
added to the parent element until the end tag is processed. So, given the
following structure:
<Window styleClasses="{foo:{...}}">
<BoxPane>
<PushButton styleClass="foo"/>
</BoxPane>
</Window>
when the styleClass attribute of the PushButton is processed, the BoxPane hasn't yet been
added to the Window, so the "foo" style class name resolves to null. :-(
I'll keep thinking about it, though. Suggestions are welcome.
Thanks,
G
