Bug 17760 – <img> treats empty src as no image at all

• Component: Images
• Status: RESOLVED FIXED

[Yuzhu Shen]

Consider the following example:

<img src="" width="100" height="100" alt="" onerror="processLoadError();">

WebKit treats src="" as no image at all and doesn't try to load. While IE and Firefox will try to load the image and (in most cases) trigger the onerror handler. (IE7 and Firefox2/3 are tested.)

The reason why IE and Firefox do so is that src="" should be regarded as a relative URI and resolved using the base URI. For example, if the base URI is "http://example.org/images/", the <img> with src="" should try to load this URI. In most cases, this will trigger onerror handler. (However, if an image "example.jpg" is set as the default document for this path, the <img> will load this "example.jpg".)

A real world example is as follows:
1. Go to http://qun.51.com/category_search.php?type1_name=%C7%E9%B8%D0%C1%BD%D0%D4
2. All missing images should be replaced with a "noclublogo.gif" (as llustrated in the snapshot).
3. WebKit doesn't do so, while IE and Firefox do.

[Yuzhu Shen]

Created attachment 19653 [details]
The snapshot.

I will upload a patch for this soon.

[Yuzhu Shen]

Created attachment 19654 [details]
The patch for this bug.

[Yuzhu Shen]

Created attachment 19657 [details]
The patch for this bug.

[Darin Adler]

Comment on attachment 19657 [details]
The patch for this bug.

This patch treats src="" the same as no src attribute at all. And the test case doesn't check for that. I think this is wrong.

To distinguish the case with no attribute at all, you should check the src value for attr.isNull().

[Yuzhu Shen]

Hi, Darin. Thanks for your reply. :)

I think it is reasonable to check whether src is null. However, I am not sure when we will get in HTMLImageLoader::updateFromElement() with src is a null string:
1) When src is not specified, we will not get into HTMLImageLoader::updateFromElement() at all.
2) And I tried in javascript "delete some_img.src" or "some_img.src = undefined". They didn't work either.
How could I write a test case to test this?

[Darin Adler]

(In reply to comment #5)
> 2) And I tried in javascript "delete some_img.src" or "some_img.src =
> undefined". They didn't work either.

Try this:

    some_img.removeAttribute("src")

That should work.

[Yuzhu Shen]

Created attachment 19832 [details]
A new patch.

Modified the code according to Darin's advice.

[Darin Adler]

Comment on attachment 19832 [details]
A new patch.

I'm pretty sure that instead of this patch you could have just changed the attr.isEmpty() to attr.isNull(); there's no reason to rearrange the code like this. I don't see any reason to not run the "load manually" case with an empty URL too.

But this is OK. r=me

[Darin Adler]

I'll take care of landing this.

[Darin Adler]

Committed revision 31097.