Difference: TWikiTemplates (2 vs. 3)

Revision 32001-09-08 - MikeMannix

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META TOPICPARENT	name="WebHome"

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new topic for the final doc

Slightly edited down, but waiting for new docs, hopefully.

see also for ref: orig TWikiTemplatingSystem

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TWiki Template System

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TWiki Template System

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< Define the templates used to render all HTML pages displayed in TWiki

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> Definition of the templates used to render all HTML pages displayed in TWiki

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Overview

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Overview

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< We have a need for more advanced template handling. As JohnTalintyre pointed out in CommonHeaderFooterTemplate it makes sense to separate the header and footer into one file so that it can be easily altered (or even overloaded by a skin). Also the oops dialog messages are all identical except for a few variables like heading, and so on.

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> The new modular template system is more flexible, efficient, and easily updated than the old set-up, where each template is a complete HTML file. The new master template approach places common templates parts, like headers and footers, in one shared file. This simplifies the conversion of templates into XHTML format, and provides a more versatile solution for templates and for skins.

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< Using external modules like the TemplateToolkit would be one way to go, but this will add a lot of baggage to TWiki.

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Major changes from the previous template system

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Needs of the TWiki templating system

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> The main difference is that templates are now defined using variables to include template parts. You change one stored instance of a common element to update all occurrences. The new system:

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Separate common parts into one (or more) base template file(s) and include that from other template files like view.tmpl.
Define common variables like a "|" separator in the base template and use them in other template files
Define variable text in templates (i.e. view.tmpl) and pass them to the base template

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separates a set of common template parts into a base template that is included by all of the related templates;

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Functional Spec

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defines common variables, like a standard separator (ex: "|"), in the base template;

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< I tried to define a simple but powerful solution that can be extended over time. Here we go:

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defines variable text in the individual templates and passes it back to the base template.

Functional Specifications

Special template directives (or preprocessor commands) are embedded in normal templates.
Use of template directives is optional, templates work without them.

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All template preprocessing is done in &TWiki::Store::readTemplate() so that the caller simply gets an expanded template file (the same as before)
Directives are of form %TMPL:<key>% and %TMPL:<key>{"attr"}%.

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All template preprocessing is done in &TWiki::Store::readTemplate() so that the caller simply gets an expanded template file (the same as before).
Directives are of the form %TMPL:<key>% and %TMPL:<key>{"attr"}%.

Initial set of directives:
- %TMPL:INCLUDE{"file"}%: Includes a template file. The usual search path is applied.
- %TMPL:DEF{"var"}%: Define a variable. Text between this and the END directive is not returned, but put into a hash for later use.
- %TMPL:END%: Ends variable definition.
- %TMPL:P{"var"}%: Prints a previously defined variable.

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New directives can be added over time when needed, i.e. IF-THEN-ELSE.
Variables live in a global name space, there is no parameter passing.
Two pass processing, so that you can use a variable before declaring it or after.
Templates and skins work transparently and interchangeably. You could for example define a new skin just for the header & footer and keep the other template files unchanged.
Note: The template directive work only for templates, they do not get processed in topic text.

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New directives can be added over time when needed, ex: IF-THEN-ELSE.
Variables are live in a global name space, there is no parameter passing.
Two-pass processing, so that you can use a variable before declaring it or after.
Templates and skins work transparently and interchangeably. For example, you can create a skin that overloads just the twiki.tmpl, like twiki.print.tmpl, that redefines the header and footer.
Note: The template directives work only for templates, they do not get processed in topic text.

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Examples

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New Template System by Example

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< Attached is an example of an oops base template oopsbase.tmpl and a example oops dialog oopstest.tmpl which is based on the base template. This is not the version that will go into the release, it is just a quick hack.

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> Attached is an example of an oops base template oopsbase.tmpl and a example oops dialog oopstest.tmpl which is based on the base template. NOTE: This isn't the release version, just a quick, simple demo.

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Base template oopsbase.tmpl

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Base template oopsbase.tmpl

The first line declares the delimiter variable called "sep", used to separate multiple link items. The variable can be called anywhere by writing %TMPL:P{"sep"}%

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> NOTE: Added a dot to escape rendering of variables, i.e. read %.WEB% as %WEB%.

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<table border="1" cellspacing="0" cellpadding="1">
<tr><td>

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</td></tr> </table >

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Test template oopstest.tmpl

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Test template oopstest.tmpl

Each oops template basically just defines some variables and includes the base template that does the layout work.

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</table >

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Sample screen shot of oopstest.tmpl

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Sample screen shot of oopstest.tmpl

With URL: .../bin/oops/Test/TestTopic2?template=oopstest&param1=WebHome&param2=WebNotify

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Comments and feedback

The itching factor to put this into the upcoming release is to easy the pending converstion of the templates into XHTML format and to have a more flexible solution for templates and skins.
Is the terminology OK?
Is the spec OK?
Are there any other directives that are needed urgently?
One drawback by using the directives is that you can only test a template from within TWiki. This is because you don't have a text that has a linear flow when you use TMPL:DEF, TMPL:P and TMPL:INCLUDE.

-- PeterThoeny - 21 Jul 2001

It's probably more readable to enforce variables being defined before use, which would avoid need for slower two-pass processing.
- [ PeterThoeny ] You need two-pass processing because you need to define the "|" separator in the included template onone side, and on the other side define variables for the included template. The processing happens as regex in memory, so there is no mesurable speed penalty.
It would be nice to simplify the syntax a bit, e.g. not using "" around variable names (they don't really need it, unlike filenames), and not using braces - however, this is not a big deal and there is some merit in keeping consistent with the current TWiki syntax.
- [ PeterThoeny ] The templating system uses the standard internal TWiki function to parse variable attributes. The "" can be skipped (is possible but is not documented).

Please have a look at the latest templates in the TWikiAlphaRelease. There is now one master template called twiki.tmpl that all other templates include (well, will include when all done). The idea is to define all common parts of the templates in twiki.tmpl and simply use that from all other templates.

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> All common template parts are defined in one master template, twiki.tmpl, that all other templates include.

Template variable:	Defines:

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%TMPL:DEF{"sep"}%

%TMPL:END%

"|" separator

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%TMPL:DEF{"sep"}%

"|" separator

%TMPL:DEF{"htmldoctype"}%

Start of all HTML pages

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%TMPL:DEF{"standardheader"}%	Standard header (for view, rdiff, ...
%TMPL:DEF{"simpleheader"}%	Simple header with reduced links (for edit, attach, oops,...)
%TMPL:DEF{"standardfooter"}%	Footer, excluding revision part and copyright part

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%TMPL:DEF{"standardheader"}%	Standard header (ex: view, index, seach)
%TMPL:DEF{"simpleheader"}%	Simple header with reduced links (ex: edit, attach, oops)
%TMPL:DEF{"standardfooter"}%	Footer, excluding revision and copyright parts

%TMPL:DEF{"oops"}%

Skeleton of oops dialog

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Example: preview.tmpl template

%TMPL:INCLUDE{"twiki"}%
%TMPL:DEF{"titleaction"}% (oops) %TMPL:END%
%TMPL:DEF{"webaction"}% *Attention* %TMPL:END%
%TMPL:DEF{"heading"}% Topic is not saved yet %TMPL:END%

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< %TMPL:DEF{"message"}% Please go back in your browser and save the topic. %TMPL:END% %TMPL:DEF{"topicaction"}% %TMPL:END%

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> %TMPL:DEF{"message"}% Please go back in your browser and save the topic. %TMPL:END% %TMPL:DEF{"topicaction"}% %TMPL:END%

%TMPL:P{"oops"}%

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Known Issues

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< With this it should be possible to create a skin that overloads just the twiki.tmpl, i.e. a twiki.print.tmpl that redefines the header and footer.

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A drawback of referring to a master template is that you can only test a template from within TWiki, where the include variables are resolved. In the previous system, each template is a structurally complete HTML document with a .tmpl filename extension - it contains unresolved %VARIABLES%, but can still be previewed directly in a browser.

-- PeterThoeny - 23 Jul 2001
-- MikeMannix - 30 Aug 2001

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