Consider for 4.1...


From: "P T Withington" <ptw@openlaszlo.org>
Date: Wed Aug 29 17:00:53 PDT 2007
Subject: Re: [Laszlo-dev] Need to be able to override resource declarations in OpenLaszlo without warnings.

Remind me why we have resources? They just seem to serve to give you a short name for a longer name. Why can't we skip resources altogether and specify the long name directly in CSS? Is this due to some underlying limitation in the SWF runtime?

On 2007-08-29, at 12:56 EDT, Elliot Winard wrote:

   I like this proposal.

That means that there are now two ways to "skin" an app -
* using CSS
* overwriting named resources

Using overwritten resources will make compile-time skinning more palatable than the 2-step CSS option we currently have. It'd still be nice to be able to support assigning of resource file-names in CSS. (LPP-3477 <http://www.openlaszlo.org/jira/browse/LPP-3477&gt;)
-e

Bret Simister wrote:
   I prefer putting the responsibility on the developer creating the library, rather than on the developer using it.

Hence,

<!-- mylibrary.lzx -->
<library>
    <resource name="logo" src="logo.png" replaceable="true" />
</library>

would allow a developer using the library to write the following

<canvas>
    <inlcude href="mylibrary.lzx" />
    <resource name="logo" src="logo2.png" />
</canvas>

and see no warnings upon compile. This seems the cleanest approach to me.
It lets the library developer be explicit about which resources were designed
to be replaced.

I am also OK with Henry's suggestion about using a compiler flag to show warnings
when you need to check for resource conflicts. The nice thing about that approach is that
it has minimal impact upon the language.

-Bret



On Wed, Aug 29, 2007 at 8:03 AM, Elliot Winard wrote:

   I can see something like that working -
<resource name="logo" src="blah.png" force="true" />

If the force attribute is present, it overwrites other declarations of logo and does *not* emit a warning.
The force attribute could mean both "replaceable" and "suppress warning".
The warning could suggest that the force attribute be used if the user intends to overwrite in case of conflict.


Resources in libraries could define the force
<library>
  <resource name="logo" src="logo.png" force="true" />
</library>

<library>
  <resource name="logo" src="logo2.png" force="true" />
</library>

Hrm. Come to think of it, that feels wrong. Would it be too much of a change if there are two new attributes for resource - force and replaceable?
@force would be tell the compiler not to emit a warning if this resource overwrites another.
@replaceable would tell the compiler not to emit a warning if this resource is overwritten

If these two attributes aren't present the current behavior remains.
So resources in Webtop libraries would look like this -
<library>
  <resource name="logo" src="logo.png" replaceable="true" />
</library>

-e

From: "Henry Minsky" <henry.minsky@gmail.com>
Having a "replace is ok" flag seems like a good solution. I wonder
which would be preferable, placing the declaration on the base library
defs, or would the user put it in their code when overriding? Or
both?



Sarah Allen wrote:
   That is exactly the dilemma. The tension is between a the frustration of an accidental override and the frustration if you want to set up your library to allow customizing a resource, where you have to provide a resource file and library separately and then the user of the library needs to create a new resource file and include all your resources except the logo and include the logo.

I suppose there could be some kind of flag that says that I meant to override this resource, like:
<resource name="logo" src="logo.png" replace="true"/>

I don't know if that would complicate the implementation or the language folk would consider it weird, but as a user of the language it would work for me.

Sarah


On Wed, Aug 29, 2007 at 5:01 AM, Elliot Winard wrote:
I don't know about removing the platform warnings.

If I include two libraries that have resources with conflicting names, I want to know about it. For example - I might include multiple libraries , each defining a 'logo' resource and expecting the logo to be sized a certain way -
   <include "mailwindow" />
   <include "stockwindow" />

I want the compiler to tell me that the stockwindow's logo is overwriting the mailwindow's logo. Warnings are informative, non-fatal and should be used to provide this kind of information.
This proposal skirts CSS altogether. If this gets implemented as proposed then the display of warnings should be configurable at compile-time. I think it would be confusing to users if resources (or classes or instances) get clobbered without any warning.
-e

Sarah Allen wrote:
    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.