Drupal 7 Module Development

Working with Files and Images
);
}
return $form;
Effect form callbacks return partial Form API structures. You only need to provide
the fields you would like users to enter, and Drupal will take care of the submission
details. We have defined two form elements to hold our configuration options,
namely, text_color and text. In general these are pretty standard Form API
arrays, but there a couple of things to point out.
Your form callback also takes a single argument—$data—which is an associative
array containing the current values of our form options, if any. You should use this
information to fill your form elements with the user's current options or, if they are
empty, to fill in sane defaults. We have set the default color here to be white, and the
default text to Drupal loves kittens!
One final thing to note is that we are using the #element_validate property to
specify an array of callbacks, which will be used to validate this specific element.
This is a Form API property we haven't seen before, but you can use it in any form
element definition. Drupal contains the function image_effect_color_validate()
to verify that hex colors are properly entered, and we take advantage of this function
by specifying it here.
Now let's make a customized message based on the user's options, to be displayed
in the image style's effect listing. This just allows us to give a little more detail to the
user, and makes it more obvious what our effect is doing.
/**
* Theme callback for image watermark effect summary output.
*
* @param $variables
* An associative array containing configuration data.
*/
function theme_watermark_summary($variables) {
$data = $variables['data'];
return t('with color @textcolor', array('@textcolor' => $data['text_
color']));
}
As you can see we just return the text we're using along with the color that
has been configured. This gets appended to the label we specified in our initial
effect declaration.
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