How to select which thumbnails sizes are displayed in srcset

Question

I know that Wordpress has its way of letting the browser decide which image to download depending on the viewport via the srcset.

I also know that I can use the_post_thumbnail function and specify a custom size, like this:

the_post_thumbnail('my-custom-size');

Now, what I would like to achieve is being able to specify a list of custom sizes (of different aspect ratio from the original image), and letting the browser decide with one to use based on the viewport.

I DON'T want to just add a custom size to the list of possibilites in srcset, I want to choose the whole list of available sizes.

I DON'T want to override the general setting of srcset of the entire website. I want to specify this list of sizes only in one section.

Is this possible?

Answer 1

The 2nd argument of the_post_thumbnail() is an array of attributes and values, so you can just set your own srcset attribute that way:

the_post_thumbnail( 
    'my-custom-size', 
    array(
        'srcset' => wp_get_attachment_image_url( get_post_thumbnail_id(), 'my-other-custom-size' ) . ' 1000w',
    )
);