Hi, added data set same as we discussed but other 3 activities are broken now, i will fix them later. do i need to make same button for data set options and slider? they have separate buttons right now.

I didn't check the behaviour yet, but I added some comments.
I think the dataset will need more information than just the operand.
The aim is to reduce the code too to have the maximum of specificities in the dataset and have a generic code where we can add other data without having to change the code.
For example, we should be able to add a modulo activity (it's just an example, it is too complicated for children but it should be possible to do so).

The other algebra activities are broken so we won't be able to merge this patch unless all the other activities are fixed.
It can be in this diff directly, either by adding multiple dataset or fixing the errors. But as we plan to change all to multiple dataset, it makes sense to convert them directly.

After testing, I noticed an issue with Options:
-When changing some options and then click "save" or "save and start", the changes are not applied directly (it keeps the settings that were there while opening the Settings page).
Wether the Activity Settings is opened from the menu or from inside the the activity doesn't make a difference.

Though, it seems to be a global issue with Options-inside-Settings page, as the same problem happens for example with the options of "Simple letters" activity.

I'm adding that to the "General TODO for multi-dataset" task.

I just made a commit on the branch to fix the issue with settings change not applied directly, and applied the fix accordingly to all activities using the DialogChooseLevel.
Note: now inside the Activities DialogChooseLevel, in onStartActivity, we need both background.stop() and background.start() , and in onSaveActivity we don't need anymore the background.stop() and background.start() .

In the process I also noticed some other general issues when pressing Cancel button:
-Dataset selection in the dialog are not restored to previous state
-In Gletters, all the options are restored correctly to previous state, except the Speed slider, so I guess we will have same issue in Algebra/other activities with a speed slider.
I'm now investigating to try to fix the second problem in Gletters, I'll let you know if I find the solution to apply it here too.

Good, I could fix the issue with Speed slider value not restored correctly after pressing Cancel in Gletters.

Just adding this line near the beginning of the fuction setDefaultValues() :

speedSlider.value = Qt.binding(function() {return activityConfiguration.speedSetting;})

see commit c10b3e0ef4f9cce4b315f6dbd18a9242207e61a0

I guess the same will be needed for algebra activities.

I added inline comments for all the needed changes after the changes I made on last commit, and all options editing will work properly.

It looks mostly good for me now.

I still have one question:
When all datasets are selected, is it intended that table of 10 is at second level, after table of 1?
I feel this is weird, and I didn't find in the code where that is defined.

I haven't tested yet but it seems good to be, only a few minor coding conventions to fix.
Thank you!

Commited in https://commits.kde.org/gcompris/ef0ffda2a553d12f9162516b140e4b476fc1889c.

Thank you!

ps: can't be closed until @timotheegiet accept the revision too