Documented default for chunk_size does not match value in code

Here's the patch:

Ok, that was my mistake. I was looking in plupload_element_pre_render() and expecting to see a #plupload_settings property with defaults filled in on the $element object. There were none. However, it doesn't matter, as you are right, that defaults are indeed being set by plupload_library().

However, there is still an issue, probably with the documentation, maybe with the code.

The documentation (README.txt) lists the default chunk_size as 1mb:

    'chunk_size' => '1mb',

However, in plupload, the default chunk_size is actually being taken from php's post_max_size var:

              'chunk_size' => parse_size(ini_get('post_max_size')) . 'b',

The reason that we weren't seeing chunking happening on file uploads is because we've got our post_max_size cranked up. We had it set so high so that we could accommodate large file uploads (as we are currently using D7 core file upload widget as well as media's file upload widget). For regular file uploads, allowable file size is constrained to that post_max_size var. I don't think it's all that uncommon for drupal sites to have a high value for that variable, especially for sites needing to accommodate large file uploads.

So perhaps the issue is the documentation, and rather than giving the default value for chunk_size as 1mb, the README should make clear that the default value is being taken from post_max_size. That would certainly be helpful to people making use of plupload.

Personally I think the default value should not be taken from post_max_size as it's very likely to be too big for the chunk size drupal site builders are looking for. I'd set it to 16mb or 32 mb. Perhaps it would better be set to the minimum of post_max_size and one of these (16mb or 32mb), because if post_max_size is small then having a higher chunk_size will break uploads. PHP's default value for post_max_size is 8mb, so maybe that's the safest size to use.

In any case, there is a discrepancy between the documented default for chunk_size and the actual default, and this discrepancy can break file upload chunking and sometimes file uploads in common site configurations. Either the documentation or the code should be changed.

This is how we are overriding the plupload module's default value for chunk_size:

/**
 * Implementation of hook_library_alter()
 */
function mymodule_library_alter(&$libraries, $module) {
  if ('plupload' == $module && isset($libraries['plupload'])) {
    if (isset($libraries['plupload']['js'][0]['data']['plupload']['_default'])) {
      $libraries['plupload']['js'][0]['data']['plupload']['_default']['chunk_size'] = '16mb';
    }
  }
}

Updated title and component to more appropriate values.