Bug 145263 - AX: <img> elements with an SVG src are ignored by VO despite valid alt attribute
Summary: AX: <img> elements with an SVG src are ignored by VO despite valid alt attribute
Status: NEW
Alias: None
Product: WebKit
Classification: Unclassified
Component: Accessibility (show other bugs)
Version: 528+ (Nightly build)
Hardware: All iOS 8.2
: P2 Normal
Assignee: Nobody
URL:
Keywords: InRadar
Depends on:
Blocks:
 
Reported: 2015-05-21 05:43 PDT by Patrick H. Lauke
Modified: 2016-08-09 13:16 PDT (History)
3 users (show)

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Description Patrick H. Lauke 2015-05-21 05:43:45 PDT
Currently, if a page has an <img src="blah.svg" alt="blah"> (with an SVG as the src), Safari/VoiceOver completely skips the image and doesn't announce the alt attribute text. Only low-impact solution I found was explicitly adding role="img" - this then makes VO behave correctly <img src="blah.svg" alt="blah" role="img">

Expected: regardless of whether it's an SVG, PNG, or whatever, the <img> should not be skipped/ignored by VO and the alt should be announced, even without role="img"
Comment 1 Radar WebKit Bug Importer 2015-05-21 05:44:03 PDT
<rdar://problem/21055846>
Comment 2 Patrick H. Lauke 2015-05-22 03:34:18 PDT
Basic test: http://codepen.io/patrickhlauke/full/XbjYGZ/
Comment 3 goetsu 2015-06-10 05:17:22 PDT
VO iOS and VO OSX do not behave exactly the same.

on an img without role="img" VO iOS do not announce the alt value when you use svg as a source but when you use an accessible svg with a role img and aria-label on it, it announce the value used for aria-label of the svg file 

with VO osX if you use an accessible svg with role img and aria-label on it, it announce correctly the alt value used on the img element
Comment 4 James Craig 2015-06-10 07:42:48 PDT
This behavior was chosen to allow access to accessible contents of SVG. We need a few test cases that include inaccessible SVG contents (as reported) and other variants so no behavior represses.
Comment 5 James Craig 2015-06-10 07:44:22 PDT
The workaround Patrick mentions removes access to the descendant contents of the SVG.
Comment 6 James Craig 2016-08-09 12:32:34 PDT
Another test case from Deque.
http://a11yideas.com/testcode/mwp/iOSsvg.html
Comment 7 James Craig 2016-08-09 12:53:58 PDT
I'm not entirely convinced this is a bug. Here's a summary of the issues at play.

1. By default, we expose SVG images as an AXGroup so that VoiceOver can navigate the descendants of accessible SVG images. (This is something of a workaround because VO on macOS assumes AXImages are leaf nodes. e.g. It assumes they contain no accessible descendants and does not interact with them. Existing VOenhancement request is pending.)
2. On these accessible SVG DOM trees, you can specify the title in contents of the SVG image, which should be spoken by VoiceOver.
3. Regardless of the role, you should be able to use the @aria-label attribute to specify the label.
4. If you use an explicit role="img" (as noted by Patrick Lauke), WebKit will expose the @alt value, but flattens the sub-DOM tree, thereby making the contents of the image non-navigable.

I think #2, #3, and #4 represent reasonable workarounds in the short term, if the authors desire is to prevent access to the sub-DOM.

If the bug report is that @alt should be used instead of the title of the src SVG, I'm not convinced it's the right thing to do, and I request more explanation.
Comment 8 James Craig 2016-08-09 13:16:55 PDT
Actually, I'm filing Deque's bug separately. Their example uses an entirely inaccessible SVG, so in that case, we should probably fall back to the behavior of a flattened bitmap image.

bug 160705 AX: @alt and bounds ignored when using img[src] points to an inaccessible SVG