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Diffstat (limited to 'includes/cbt/README')
| -rw-r--r-- | includes/cbt/README | 44 |
1 files changed, 22 insertions, 22 deletions
diff --git a/includes/cbt/README b/includes/cbt/README index cffcef2f..30581661 100644 --- a/includes/cbt/README +++ b/includes/cbt/README @@ -1,7 +1,7 @@ Overview -------- -CBT (callback-based templates) is an experimental system for improving skin +CBT (callback-based templates) is an experimental system for improving skin rendering time in MediaWiki and similar applications. The fundamental concept is a template language which contains tags which pull text from PHP callbacks. These PHP callbacks do not simply return text, they also return a description of @@ -15,24 +15,24 @@ efficiency gains and techniques. TemplateProcessor was the first element of this experiment. It is a class written in PHP which parses a template, and produces either an optimised template with dependencies removed, or the output text itself. I found that even with a heavily optimised template, this processor was -not fast enough to match the speed of the original MonoBook. +not fast enough to match the speed of the original MonoBook. To improve the efficiency, I wrote TemplateCompiler, which takes a template, preferably pre-optimised by TemplateProcessor, and generates PHP code from it. The generated code is a single expression, concatenating static text and -callback results. This approach turned out to be very efficient, making -significant time savings compared to the original MonoBook. +callback results. This approach turned out to be very efficient, making +significant time savings compared to the original MonoBook. -Despite this success, the code has been shelved for the time being. There were +Despite this success, the code has been shelved for the time being. There were a number of unresolved implementation problems, and I felt that there were more pressing priorities for MediaWiki development than solving them and bringing -this module to completion. I also believe that more research is needed into +this module to completion. I also believe that more research is needed into other possible template architectures. There is nothing fundamentally wrong with the CBT concept, and I would encourage others to continue its development. The problems I saw were: -* Extensibility. Can non-Wikimedia installations easily extend and modify CBT +* Extensibility. Can non-Wikimedia installations easily extend and modify CBT skins? Patching seems to be necessary, is this acceptable? MediaWiki extensions are another problem. Unless the interfaces allow them to return dependencies, any hooks will have to be marked dynamic and thus inefficient. @@ -51,14 +51,14 @@ The problems I saw were: Template syntax --------------- -There are two modes: text mode and function mode. The brace characters "{" +There are two modes: text mode and function mode. The brace characters "{" and "}" are the only reserved characters. Either one of them will switch from -text mode to function mode wherever they appear, no exceptions. +text mode to function mode wherever they appear, no exceptions. In text mode, all characters are passed through to the output. In function -mode, text is split into tokens, delimited either by whitespace or by +mode, text is split into tokens, delimited either by whitespace or by matching pairs of braces. The first token is taken to be a function name. The -other tokens are first processed in function mode themselves, then they are +other tokens are first processed in function mode themselves, then they are passed to the named function as parameters. The return value of the function is passed through to the output. @@ -68,39 +68,39 @@ Example: First brace switches to function mode. The function name is escape, the first and only parameter is {"hello"}. This parameter is executed. The braces around the parameter cause the parser to switch to text mode, thus the string "hello", -including the quotes, is passed back and used as an argument to the escape -function. +including the quotes, is passed back and used as an argument to the escape +function. Example: {if title {<h1>{title}</h1>}} -The function name is "if". The first parameter is the result of calling the +The function name is "if". The first parameter is the result of calling the function "title". The second parameter is a level 1 HTML heading containing -the result of the function "title". "if" is a built-in function which will +the result of the function "title". "if" is a built-in function which will return the second parameter only if the first is non-blank, so the effect of this is to return a heading element only if a title exists. As a shortcut for generation of HTML attributes, if a function mode segment is -surrounded by double quotes, quote characters in the return value will be -escaped. This only applies if the quote character immediately precedes the +surrounded by double quotes, quote characters in the return value will be +escaped. This only applies if the quote character immediately precedes the opening brace, and immediately follows the closing brace, with no whitespace. -User callback functions are defined by passing a function object to the +User callback functions are defined by passing a function object to the template processor. Function names appearing in the text are first checked against built-in function names, then against the method names in the function -object. The function object forms a sandbox for execution of the template, so +object. The function object forms a sandbox for execution of the template, so security-conscious users may wish to avoid including functions that allow arbitrary filesystem access or code execution. -The callback function will receive its parameters as strings. If the -result of the function depends only on the arguments, and certain things +The callback function will receive its parameters as strings. If the +result of the function depends only on the arguments, and certain things understood to be "static", such as the source code, then the callback function should return a string. If the result depends on other things, then the function should call cbt_value() to get a return value: return cbt_value( $text, $deps ); -where $deps is an array of string tokens, each one naming a dependency. As a +where $deps is an array of string tokens, each one naming a dependency. As a shortcut, if there is only one dependency, $deps may be a string. |