[webkit-gtk] WebKit not rendering images of a local resource (from within Gedit)

[Gavin Lambert]

On 20 January 2015 09:56, quoth Peter Bittner:
> Now it looks like WebKit is rendering images from remote resources (e.g.
> http://farm3.static.flickr.com/2256/2259897373_d47ecf0983_o_d.png)
> fine, but local images (e.g. docs/reStPlugin.png) just display as an empty
> box. Interestingly, the size of the box corresponds to the real size of
the
> image, but the image itself is not displayed.
> 
> The box around the image is displayed only when the file exists, otherwise
> only the ALT-text is visible. Looks like WebKit reads the image dimensions
> out of the image file. I've tried setting a <base href="file://..."> tag
in
> the HTML head section, but that makes things worse ("** Message: console
> message:  @318: Not allowed to load local
> resource: file:///home/.../doc/reStPlugin.png")
> 
> Some details and a screenshot are available from a bug report at
> https://github.com/bittner/gedit-reST-plugin/issues/7
> Carlos from the webkit-dev mailing list suggested "passing the right base
URL
> to the load method" may be missing
> (https://lists.webkit.org/pipermail/webkit-dev/2015-January/027156.html).

It's a standard security feature of modern browsers to block all access to
file:// URIs from pages loaded from anything other than a file:// URI.  So
if you want to render the content, you have to let the browser know that
it's loading a local file.  If you're passing the file:// URI to
webkit_web_view_load_uri, this should be automatic.  If you're using
webkit_web_view_load_string, you need to specify an appropriate file:// URI
as the base in the final parameter.  (This does not need to actually exist
as a file, but it will be used as the base for relative links.)

It's not sufficient to use <base href> in the HTML content itself, as this
is inherently untrustworthy for this purpose -- imagine if an HTML file on
the public internet specified this, and then started trying to load your
local files.

You *might* also need to set the "enable-file-access-from-file-uris"
property to true on webkit_web_settings as well, but I'm not sure exactly
what this affects.  Try it without that first.