Bug 177068 – Creating a picture element with a source and img element triggers loading of both sources

• Status: RESOLVED
• Resolution: DUPLICATE
• Component: Images

Created attachment 321087 [details]
Reduced test case

When an image element is created:

> const image = document.createElement('img');
> image.setAttribute('srcset', 'https://via.placeholder.com/300x100/0e7f00');

webkit starts preloading the srcset immediately.

However, when an image is intended to become part of a picture tag:

> const picture = document.createElement('picture');
> const source = document.createElement('source');
> const image = document.createElement('img');
> 
> source.setAttribute('sizes', '100vw');
> source.setAttribute('media', '(orientation: portrait)');
> 
> image.setAttribute('sizes', '100vw');
> image.setAttribute('alt', 'Placeholder'); 
> 
> source.setAttribute('srcset', 'https://via.placeholder.com/550x900/6600af 550w, https://via.placeholder.com/750x1000/a100af 750w'); 
> image.setAttribute('srcset', 'https://via.placeholder.com/300x100/0e7f00'); 
> 
> picture.appendChild(source);
> picture.appendChild(image);

I expect either the source or the image to be loaded depending on the media query, not both.

# Actual
Webkit preloads the image tag, and the source tag when it is added to the picture element.

# Expected
Only the source tag to be loaded when (orientation: portrait) or only the img to be loaded when (orientation: landscape).


Chrome handles this scenario correctly by cancelling the initial request for the image's srcset when it becomes a child of the picture element.

Reduced test case: https://s.codepen.io/maximus8891/debug/LzVjNZ/ZorBajwPWeOM

Possible duplicates:
https://bugs.webkit.org/show_bug.cgi?id=6656
https://bugs.webkit.org/show_bug.cgi?id=35377

[Radar WebKit Bug Importer]

<rdar://problem/34500892>

[Said Abou-Hallawa]

This is the same as bug 159484. They both address the issue of loading multiple resources for the same <picture> element although a single resource will be displayed at the end.

*** This bug has been marked as a duplicate of bug 159484 ***