[RFC] Template procedures

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APTX
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[RFC] Template procedures

Post by APTX » Fri Aug 01, 2008 3:55 pm

This is something, that IIRC was not requested by anyone. I had this idea today and wanted to see if something like this is possible with the current template engine. Turns out it is. :)

Procedures in templates is just some template code you can use wherever and as many times as you like. It has no understanding of scope.

Syntax
A simple procedure:

Code: Select all

<!-- PROCEDURE my_procedure -->
	hello world<br />
<!-- ENDPROCEDURE -->
As you surely know, it will print "hello world<br />".

You can use any tags (except PROCEDURE) in a procedure:

Code: Select all

<!-- PROCEDURE my_procedure -->
	hello world<br />

	{S_USERNAME}<br />

	<!-- IF 1 -->
		{$FOO}<br />
	<!-- ENDIF -->

	{L_WHO_IS_ONLINE}<br />

	<!-- INCLUDE forumlist_body.html --><br />

<!-- ENDPROCEDURE -->
Procedures are invoked using the CALL tag:

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<!-- CALL my_procedure -->
The argument to the CALL tag can be a variable:

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<!-- PROCEDURE my_procedure -->
	hello world<br />
<!-- ENDPROCEDURE -->

<!-- DEFINE $MY_PROCEDURE = 'my_procedure' -->
<!-- CALL $MY_PROCEDURE -->
As there is no scope things like this will work:

Code: Select all

<!-- PROCEDURE my_procedure -->
	$VARIABLE is {$VARIABLE}
<!-- ENDPROCEDURE -->
<!-- DEFINE $VARIABLE = 'hello world' -->
<!-- CALL my_procedure -->
... and print "VARIABLE is hello world"

The code is attached to this post. Is it worth adding it to trunk?
Attachments
functions_template.php.txt
(23.02 KiB) Downloaded 564 times
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Kellanved
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Re: Template procedures

Post by Kellanved » Fri Aug 01, 2008 4:27 pm

I vote "yes". Very nice.
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naderman
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Re: Template procedures

Post by naderman » Fri Aug 01, 2008 10:01 pm

Slowly I'm starting to wonder why we don't just use PHP instead of our own template language?

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DavidMJ
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Re: Template procedures

Post by DavidMJ » Sat Aug 02, 2008 5:39 am

naderman wrote:Slowly I'm starting to wonder why we don't just use PHP instead of our own template language?
It would be too easy to cheat and do bad things in template land... They would also be harder to verify by the styles team... Our system is very nice for lots of loops
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APTX
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Re: Template procedures

Post by APTX » Sat Aug 02, 2008 11:04 am

naderman wrote:Slowly I'm starting to wonder why we don't just use PHP instead of our own template language?
The most important reason is the ease of use. Would you really want to write templates like the compiled ones?
It is much harder to break things by in templates. The only way to break something is to make syntax errors.
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Acyd Burn
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Re: Template procedures

Post by Acyd Burn » Sat Aug 02, 2008 11:15 am

naderman wrote:Slowly I'm starting to wonder why we don't just use PHP instead of our own template language?
Not using PHP on the user-facing side does not only has benefits for controlling what is possible and not, but also for not putting too much code logic into templates (something i utterly hate in smarty), as well as being a well-understood format [html-comments] (the format is something i utterly hate in smarty and php templates) - which comes with correct syntax highlighting. Another benefit is us using .html (here, php parsing is not allowed, or should not). If you would use .php, style authors would need to use echo or heredoc or even opening/closing php tags - can you imagine the mess? Stylers do not necessarily know PHP - they normally do not even know what it is at all.

No, i really like our template engine and i think it is the best part in phpBB 2.0.x for example and moreso in phpBB 3.0.x. Do not go back to the 1.0.x times...

Re procedures:

Where would someone define those? Since these are procedures i think they are mostly not defined within the same file they are used in?
What are the benefits, the real world uses? Could you give a real-world example where it is really beneficial?

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Kellanved
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Re: Template procedures

Post by Kellanved » Sat Aug 02, 2008 11:39 am

Essentially we are doing it with include now - jumpbox.html and the other very small template files are in effect "procedures".
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Re: Template procedures

Post by DavidMJ » Sat Aug 02, 2008 3:31 pm

a) I suggest a nicer name, like SNIPPET
b) does it make sense to allow us to pass a parameter or no?

Other than that, it looks pretty good.

Btw, any hope of support for arbitrary general expressions in places like DEFINE?
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Re: Template procedures

Post by APTX » Sat Aug 02, 2008 4:55 pm

Acyd Burn wrote:Where would someone define those? Since these are procedures i think they are mostly not defined within the same file they are used in?
They can be defined anywhere. It's implemented as PHP functions so it can be used like PHP functions. ;)
Acyd Burn wrote:What are the benefits, the real world uses? Could you give a real-world example where it is really beneficial?
I didn't have anything in mind while writing this.
DavidMJ wrote:b) does it make sense to allow us to pass a parameter or no?
Sense? Yes, of course it makes sense! To make normal functions these procedures would need to be able to take arguments. To allow them that the template engine would have to understand scope and for the arguments to be useful you'd need that "arbitrary general expressions" support.
DavidMJ wrote:Btw, any hope of support for arbitrary general expressions in places like DEFINE?
There's always hope. :P
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Acyd Burn
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Re: Template procedures

Post by Acyd Burn » Sun Aug 03, 2008 9:50 pm

Personally i think without any real world usage it is pointless to add something like this to the template engine. Our strength comes from simplicity - do not try to go the Smarty route in implementing anything and everything and trying to mimick PHP in a template engine. I still want to hear real usage examples. For example, could it be used to generate something for the "User name and colouring"? We have one function within phpBB to do it, we have several different places where we display coloured usernames and groups and basically everywhere we use the same HTML "Snippet". Additionally, it really does not make sense to just say: "Define it where you want" - it has to be determined where the best place would be. As i see it, the feature is meant to make these snippets available on every pageview, be it viewtopic or viewforum - but what are the benefits if you need to add them to both template files. Overall header is also not really the right place. So, best would be maybe an INCLUDE in overall_header. We want to split up template files a bit more anyway.

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