> I'm going to look into getting PMA_mimeDefaultFunction() function inside
> PMA_DisplayResults class. (currently it is under core.lib.php)
> I think it is possible to use this function inside that class, and call
> directly ($this->_mimeDefaultFunction()) instead of using additional string
> to store method name. (current way)
>
> Then the default function for the mime transformation is inside a class.
> But the other existing transformations functions are still global functions.
> If that is not good (feels not good), those also should convert to classes.

I've seen that the PMA_mimeDefaultFunction is only currently used in
DisplayResults.class.php, so I think it's a good idea to move it there.

> And if other transformations converted to classes, in which way I can create
> objects of those classes.
> Should I need to use string to store the class name and then use it as
> belows.
>
> $class_name = 'TestClass';
> $ob = new $class_name($params);
>
> It is very helpful for me if you can share your suggestions.

As general info, to use a transformation plugin, you have to include it and
then instantiate it. For example, if you want to use Text_Plain_Sql:
 include_once 'libraries/plugins/transformations/Text_Plain_Sql.class.php';
 $plugin_manager = null; // Still working on this, so you can use null for now
 $sql_transf = new Text_Plain_Sql($plugin_manager);
Then, you can use the actual transformation by calling:
 $sql_transf->applyTransformation();

In DisplayResults.class.php, inside _getTableBody(), there is an init:
[2158] $default_function = 'PMA_mimeDefaultFunction'; // default_function
Then, this variable is passed as an argument to several functions along
the way:
 _getDataCellForNumericColumns,
 _getDataCellForBlobColumns,
 _getDataCellForGeometryColumns,
 _getDataCellForNonNumericAndNonBlobColumns,
 _getRowData,
 _addClass
 _handleNonPrintableContents

Some of the functions only pass it further, while others use actually use it.
I replaced the use of the PMA_transformation_[FILENAME]() with the
use of $transformation_plugin->applyTransformation() and kept the same
arguments.
So I had to pass an instance of the transformation class as an argument
($transformation_plugin), but my problem was that in some cases I had to use
the applyTransformations method, while in others, I had to use the default
function ( PMA_mimeDefaultFunction() ). Therefore, where needed, I set the
argument $transformation_plugin = $default_function, and, in the above
mentioned methods I checked and used accordingly, something similar to:
$result = ($transformation_plugin != $default_function
   ? $transformation_plugin->applyTransformation(
       $data,
       $transform_options,
       $meta
   )
   : $default_function($data)
)

Hope that helps. I will write some wikis for all of the plugins, but I thought
I should first finish the whole system (the plugin managers).