How adjust "Maximum upload size" indicator for file upload?

Question

Joomla prints a short notice regarding the Maximum upload size when including a file upload field with the standard form field file, see code and image below:

<field
    name="image"
    type="file"
    label="COM_EXAMPLE_PICTURE_LABEL"
    description="COM_EXAMPLE_PICTURE_DESC" 
    accept="image/*"
/>
<field
    name="MAX_FILE_SIZE"
    type="hidden"
    default="2097152"
/>

The Joomla docs for file mentions adding a hidden field to set the maximum file size. It's not entirely clear if Joomla does anything with that field or if all the logic needs to implemented in the controller (e.g. in the save method).

You can put a soft limit file size by adding a hidden field with name="MAX_FILE_SIZE" and value the maximum allowed bytes which is handled by php, but you must also handle it in your code with or without it.

However, that wouldn't change the way the field is displayed. Is there a way to show a different maximum file size?

It looks like that message is set in layouts/joomla/form/field/file.php:

...

$maxSize = JHtml::_('number.bytes', JUtility::getMaxUploadSize());

...

    <?php echo JText::sprintf('JGLOBAL_MAXIMUM_UPLOAD_SIZE_LIMIT', $maxSize); ?>

PS: I don't what to change the upload_max_filesize for PHP in the php.ini, just for this particular form.

Update

Using the approach suggested by Lodder, I added a file components/com_YOURCOMP/layouts/joomla/form/field/file.php to my component and copied the content of layouts/joomla/form/field/file.php. Then I replaced the line

$maxSize = JHtml::_('number.bytes', JUtility::getMaxUploadSize());

by

$xmlData = simplexml_load_file(JPATH_COMPONENT . '/models/forms/add-form.xml');

$fieldMaxSize = $xmlData->xpath('//field[@name="MAX_FILE_SIZE"]');

if (isset($fieldMaxSize[0]['default']) && !empty($fieldMaxSize[0]['default'])) 
{
    $sizeValue = $fieldMaxSize[0]['default'];
} 
else 
{
    $sizeValue = JUtility::getMaxUploadSize();
}
$maxSize = JHtml::_('number.bytes', $sizeValue);

Answer 1

If you'd like to perform this override for all file form fields only within your component, then you can override the layout at component level.

To do this copy the following layout:

layouts/joomla/form/field/file.php

to:

components/com_YOURCOMP/layouts/joomla/form/field/file.php

If the form field reside in the administrator views, then copy the layout to:

administrator/components/com_YOURCOMP/layouts/joomla/form/field/file.php

Once done, you can make the necessary changes to the layout without it affecting the visual aspects anywhere else on the site.