I've got to second Thomas on this point - adding a new user.agent is very
non-trivial at least without an overhaul of CssResource generation. In GXT
3 we took the route of providing our own PropertyProviderGenerator and
adding a few new user agents (ie7, ie10 for a start), but quickly found
that doing this broke internals of a variety of GWT widgets. The fallback
attribute let ie7 behave as ie6 (and ie10 as ie9) if a replace-with rule
set did not define specific behavior for it, but the CssResource generation
process creates types based on all properties available, not just the
properties that the CSS file was written to expect. This means that if you
have
@if user.agent ie6 ie8 {
//...
}
then the enclosed content will only be in the _ie6 and _ie8 generated
classes, not _ie9 (good), _ie10 (good), or ie7 (bad). Without a fallback
mechanism that makes sense in CssResource, any existing GWT widget that
uses ClientBundle may be unusable in a project that builds its own user
agents.
This is the only case we ran into before we decided it wasn't worth it -
GXT 3 can and should run along side or in conjunction with standard GWT
widgets, so this was a deal-breaker right off the bat.
On Wed, Sep 11, 2013 at 4:40 AM, Thomas Broyer <t.bro...@gmail.com> wrote:
>
> On Wednesday, September 11, 2013 3:10:56 AM UTC+2, Goktug Gokdogan wrote:
>>
>> I recently noticed that developers are forking c.g.gwt.useragent in order
>> to be able to add new browser permutations to existing ones. This is
>> suboptimal and causes code duplication and possibly trying keep it in sync
>> with the original during updates.
>> The root cause of this is the determination of user.agent during runtime
>> is statically defined in this package. I created a patch so that code
>> snippets to extract user agent can be defined and injected from outside so
>> that new permutations can be added externally without forking the original
>> package.
>>
>> If you hit this issue before, please take a look at https://gwt-review.**
>> googlesource.com/4500 <https://gwt-review.googlesource.com/4500> and see
>> if would make your life easier.
>>
>
> Not opposed to it in principle, but adding a new user.agent is not an easy
> task, and more often than not people actually want to add a new property to
> be used in conjunction to user.agent in deferred-binding rules (e.g.
> https://code.google.com/p/google-web-toolkit/wiki/ConditionalProperties#Example_2:_Avoiding_permutation_explosion);
> so I'm not sure this is the right move, as it makes it easier to do things
> the wrong way.
>
> As a side note, I think we should add a way to "alias" property values so
> we can progressively rename "gecko1_8" to "gecko" and possibly "safari" to
> "webkit" [1] without breaking anyone. I think this can be "faked" today
> using fallback-value and excluding the fallback value from the possible
> values (i.e. <extend-property name="user.agent" value="gecko"
> fallback-value="gecko1_8"/><set-property name="user.agent"
> value="ie6,ie8,ie9,gecko,safari,opera"/> notice the absence of "gecko1_8"
> here but thanks to the fallback-value, <if-property-is name="user.agent"
> value="gecko1_8"/> should continue to work and match the "gecko"
> permutation) but we cannot <set-property> the user.agent property in GWT
> proper as it would break those who new values and expect the set of
> "possible values" to automatically grow with their new value.
>
> [1] Daniel thinks we should add a "chromium" permutation –he said "blink",
> but I believe "chromium" would be a better name: it's not only about the
> rendering engine, but also the JS engine–, I know "webkit" can be used with
> other JS engines than JavaScriptCore but I'm unsure anyone would do it
> nowadays, and "webkit" probably still better matches reality than "safari".
>
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