https://bugs.kde.org/show_bug.cgi?id=509711
Bug ID: 509711
Summary: Random wallpaper order: Non-ideal solution for
avoiding a duplicate item when slideshow restarts
Classification: Plasma
Product: plasmashell
Version First 6.4.90
Reported In:
Platform: Other
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: Image & Slideshow wallpaper plugins
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Target Milestone: 1.0
SUMMARY
In the image slideshow, when a random order is selected and all items of the
current list were consumed and the next set of items is queued, the solution
for avoiding a duplicate item selection in the transition is not ideal and
leads to skipping one of the items.
The `ImageBackend::nextSlide()` function currently does this:
https://invent.kde.org/plasma/plasma-workspace/-/blob/v6.4.90/wallpapers/image/plugin/imagebackend.cpp#L411-420
- When the end of the slideshow has been reached (index is 0 again), reshuffle
it (`invalidate()`)
- Set the next item to the item with index 0
- If the previous item is the same as the next item, increase the index by 1
and set next that instead
This means that the item with index 0 will not be shown in this case, as it's
simply skipped due to it being the same as the previous one, as a valid
wallpaper transition needs to be ensured.
A more sensible idea would be swapping the first item with item [2...n] of the
reshuffled list, so that no item is skipped and every item will be shown.
>From looking at the code (I'm neither familiar with C++/Qt nor with the
plugin's implementation), it seems like this was the simplest solution, as
there's no interface on the `SlideFilterModel` class for swapping specific
items:
https://invent.kde.org/plasma/plasma-workspace/-/blob/v6.4.90/wallpapers/image/plugin/slidefiltermodel.h#L17
Alternatively, the slideshow could be reshuffled again until the first item is
not the previous one, but this of course doesn't work in constant time.
STEPS TO REPRODUCE
Have a wallpaper image slideshow in random order with at least 3 items
OBSERVED RESULT
Current slideshow:
A B C
Potential next slideshows:
A B C
A C B
B A C
B C A
A B (C was skipped)
B A (C was skipped)
EXPECTED RESULT
Current slideshow:
A B C
Potential next slideshows:
A B C
A C B
B A C
B C A
A C B (via C A B)
B A C (via C A B)
B C A (via C B A)
A B C (via C B A)
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