Incorrect interpretation of CSS @import

[pepak]

Calibre 5.xx (all versions up to at least 5.20) incorrectly interprets @import url(...) rules in CSS sheets (when relative URLs are used. According to W3 ( http://www.w3.org/TR/REC-CSS1/#url ), partial (e.g. relative) URLs should be interpreted "relative to the source of the style sheet, not relative to the document". Calibre 5.xx does not do that - I wasn't able to verify it exactly, but the observed behavior is consistent with Calibre interpreting relative urls as relative to the first CSS in the chain. Calibre 4.xx used a correct interpretation.

Attached example demonstrates the problem. We have the following files:

test.htm
test.css
a/test.css
a/b/test.css

Test.htm loads a/b/test.css using <link rel="stylesheet" href="a/b/test.css" type="text/css"/> and as far as I can tell, Calibre can process that correctly. a/b/test.css then loads a/test.css using @import url('../test.css'), and this also gets interpreted correctly by Calibre. Then a/test.css tries to load test.css using @import url('../test.css') and this will crash Calibre (but not a browser). As far as I can tell, the last @import rule will incorrectly try to load a/test.css again, and again, and again until it exhausts the stack.

I reported a similar error some time ago ( https://bugs.launchpad.net/calibre/+bug/1901278 ) and that received a fix, but apparently it was only a partial fix - it resolved the specific case described in that bugreport, but the incorrect behavior remained.

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.

 status fixreleased