Jonathan Watt [:jwatt] Reporter
	Description • 7 years ago

In addition to image/bmp, we also support image/x-ms-bmp. Chrome does not support this unofficial MIME type though, so this seems unnecessary.

	Timothy Nikkel (:tnikkel)
	Comment 3 • 7 years ago
mozreview-review

Comment on attachment 8934313 [details]
Bug 1422725 - Remove support for the image/x-ms-bmp MIME type.

https://reviewboard.mozilla.org/r/205232/#review210824

	Jonathan Watt [:jwatt] Reporter
	Comment 4 • 7 years ago

(In reply to Jonathan Watt [:jwatt] (needinfo? me) from comment #0)
> Chrome does not support this unofficial MIME type though

Or, more specifically:

 * For an embedded image load (HTML <img> etc.) the MIME type
   seems unimportant - Chrome presumably sniffs the contents and
   correctly detects the image as BMP and displays it even if
   served with some junk MIME type.

 * A top-level load of a BMP image served over HTTP as image/x-ms-bmp
   will cause Chrome to download it instead of displaying it as
   it will do if served as image/bmp

 * A top-level load of a BMP image from the local file system via a
   file:// URL will display correctly though, even if the MIME type
   the system associates with .bmp images is image/x-ms-bmp
   (as revealed by `file --mime-type some.bmp`). Presumably Chrome is
   also sniffing the contents for local files (.bmp files will still
   display correctly even if the file extension is changed to some
   random, unrecognized extension).

The patch to remove support for image/x-ms-bmp from Mozilla makes us behave in the same way...except on Linux apparently, where top-level loaded local BMP files served as image/x-ms-bmp appear to fail:

https://treeherder.mozilla.org/#/jobs?repo=try&revision=4139bf52f17a14cdec4b84c51201e543a72beeb1

I'm not sure why we're behaving differently on Linux. Unfortunately a VMware update has trashed my Ubuntu install and I've now wasted many hours without success trying to get a functioning new Ubuntu install up and running.