[Andreas]

Hmm, it's documented - you just have to look

/**
* This variable prevents the pre_save() method from being called more than once.
* In some classes, it is helpful to explicitly call pre_save() before
* calling save as additional checks are done. This variable is used to prevent
* pre_save() from being executed when save() is called. If null, pre_save()
* has yet to be called; else, it is the return value of pre_save().
*
* @var	null|bool
*/
var $presave_called = null;

/**
* Any checks to run immediately before saving. If returning false, the save will not take place.
*
* @param	boolean	Do the query?
*
* @return	boolean	True on success; false if an error occurred
*/
function pre_save($doquery = true)

PHP Code:

 if ($this->presave_called !== null)
{
return $this->presave_called;
} 


Check if it was called already, if this is the Case return the previous result.

PHP Code:

if (!parent::pre_save($doquery))
{
$this->presave_called = false;
return false;
} 


If pre_save() fails in the Parent-Class it's failed.

PHP Code:

if (!$this->pre_save_post($doquery))
{
$this->presave_called = false;
return false;
} 


If pre_save() for the Post failed, pre_save() for the Thread failed.

dateline? username? post? Where are they getting all this from?

These are required Fields, so they must be present upon saving, eg. can be loaded with fetch_field():

PHP Code:

/**
* Fetches info about the current data object - if a new value is set, it returns this, otherwise it will return the existing data
*
* @param    string    Fieldname
*
* @return    mixed    The requested data
*/
function &fetch_field($fieldname, $table = null)
{
    if ($table === null)
    {
        $table =& $this->table;
    }

    if (isset($this->{$table}["$fieldname"]))
    {
        return $this->{$table}["$fieldname"];
    }
    else if (isset($this->existing["$fieldname"]))
    {
        return $this->existing["$fieldname"];
    }
    else
    {
        return null;
    }
}