I think this is an excellent proposal. cc'ing laszlo-user to see if
other folks developing in LZX have strong feelings about this ...
On Tue, Aug 28, 2007 at 3:12 PM, Bret Simister wrote:
Currently, in the OpenLaszlo platform, it was decided that declaring a
resource twice within an LZX app
causes a server warning. This was intended to help developers just in
case they accidentally overrode a
resource that had already been declared in another library.
<!-- the following code produces a warning, but still compiles -->
<canvas>
<resource name="logo" src="logo.gif" />
<resource name="logo" src="logo2.gif" />
<!-- view appears with logo2.gif -->
<view resource="logo" />
</canvas>
At this time, I would suggest that the platform remove these warnings
and have
the last resource declaration override all other previous declarations.
Here is why...
OpenLaszlo now has a CSS implementation. It gives developers an elegant
method
of skinning their applications. This works, currently, by first
declaring a resource
<resource name="someimage_rsc" src="somepath/someimage.jpg" />
and then referring to that resource in a CSS selector
view[name="someview"] {
resource: someimage_rsc;
}
If a developer builds a library ....
myCustomLibrary ( folder )
library.lzx
myresources.lzx ( contains many resource definitions including
'lowerRightCorner_rsc' )
mystyles.css ( contains many selectors including one that
references 'lowerRightCorner_rsc' )
... ( other class and source image files )
where library.lzx includes both myresources.lzx and mystyles.css
Then library can be used with a simple inclusion in the main app.
<canvas>
<include name="myCustomLibrary" />
<!-- instance of a class from myCustomLibrary -->
<mycustomclass />
</canvas>
Let's assume that " mycustomclass " contains a number of resources, and
that you ( as a developer )
only want to change one of those resources . The simplest method to
accomplish this would be ...
<canvas>
<include name="myCustomLibrary" />
<!-- override resource definition "lowerRightCorner_rsc" defined earlier
in myresouces.lzx -->
<resource name="lowerRightCorner"
src="my_new_path/my_lower_right_corner.jpg" />
<!-- instance of mycustomclass that will now display
the new resource based on the unchanged css selector -->
<mycustomclass />
</canvas>
Currently, this code would cause a compiler warning. To avoid these
warnings ( without changing OpenLaszlo ) the resouces.lzx file(s) and
possibly the library .lzx would have to be edited.
If instead, we allow for resource overriding, then ...
1) the original CSS and resource files will remain unchanged
2) The old resource for " lowerRightCorner" would NOT be included in
the app
3) There would be clean separation between external libraries and the
skinning of theses libraries included in an application.
