Some snippets have yet to be converted due to the more complex nature
of those snippets, and to keep things neat a separate commit makes more
sense for those.
Last time I touched this code, I went in looking for a specific problem,
and came out with a fix specific to that issue. That fix was not wrong,
yet it hardly covered all the problems present in the code once one took
into account issues like:
- local vs remote resources,
- relative vs absolute paths,
- different operating systems behaving differently, and
- Qt being uniquely buggy on different platforms.
The major part of it was fixed by using QUrl.fromUserInput(), which does
the exact kind of auto-detection for the nature of the resource that we
were in need of.
The rest of the issues were fixed by creating a number of test cases and
fixing problems as they popped up. Testing was done in Windows & Ubunty
against the above-mentioned test cases, which can be found in PR #629.
Regarding ImageTooltip.supportedSchemes
When QUrl.fromUserInput() misidentifies the scheme on Linux, it causes
all resemblance between the original request and the reply.request() in
the finished() signal to be lost, which results in this item getting
stuck in the ImageTooltip processing pipeline.
Limiting the supported schemes to the ones most commonly encountered
('file', 'http', 'https' and the schema-less local paths) is the only
reliable method I have found to work around this particular bug in Qt.
Issue #549 was caused because the request and reply object urls are not
guaranteed to be the same. Redirects are the most common cause, but a
malformed URL apparently also qualifies. We now make sure to look at the
original request.
Because the code confused me while I was working on it, I decided to
refactor and document it in order to understand what was going on. I am
glad I did: I found another crashing bug involving the rapid-firing of
tooltip requests, and the processing dict never had its entries removed
either, leading to a (very slow) memory leak over time.
All is good in the world of image tooltips now.
