[SalesForce] Increase length of custom text field when the field has data

What you have in your screen shot is a field "Name Field" for a custom object. If i remember right, it is limited to 80 characters which cannot be expanded.

@keith-c is right that the layouts work in combination with the field security set in the profile. The use case for that is two users with different profiles who share the same layout. One profile can access Field A while the other profile cannot. In this case, you don't have to build two different layouts.

If you're wanting to do this exclusively through the Metadata API, you'd need to also deploy modified versions of all your profiles which include the new field's visibility settings.

Here's an example of the elements you'd need in the profile:

<fieldPermissions>
    <editable>true</editable>
    <field>Contact.Gender__c</field>
    <readable>true</readable>
</fieldPermissions>

Note that it's probably a good idea to retrieve the profiles first before editing them. If you are working with an older copy of the profile on disk you might wind up deploying the older version and overwriting other changes made to the profile.

Here's the relevant Metadata API docs: http://www.salesforce.com/us/developer/docs/api_meta/Content/meta_profile.htm#profilefieldlevelsecurity_title