MudTreeviewItem: Fix checkbox in multi-selection mode

[henon]

Resolves #8940

Type of Changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (fix or improvement to the website or code docs)

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 90.47%. Comparing base (28bc599) to head (b92666a).
Report is 180 commits behind head on dev.

Files	Patch %	Lines
...lazor/Components/TreeView/MudTreeViewItem.razor.cs	0.00%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #8948      +/-   ##
==========================================
+ Coverage   89.82%   90.47%   +0.64%     
==========================================
  Files         412      419       +7     
  Lines       11878    12192     +314     
  Branches     2364     2380      +16     
==========================================
+ Hits        10670    11031     +361     
+ Misses        681      628      -53     
- Partials      527      533       +6     

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[Yomodo]

@henon I found 2 more issue, clicking the first node skips the nested subitems node:

Multi selection:
Selecting all now shows indeterminate state:

[ScarletKuro]

@henon do we reopen this issue or shall we create new one?

[henon]

No need, I'll directly PR a fix

[henon]

Multi selection: Selecting all now shows indeterminate state:

This is intended behavior, you shouldn't confuse this example with the custom logic one. Here selecting the parent just selects it and not its children. Conversely selecting all its children doesn't automatically select the parent. That is exactly why we have the custom checkbox example to show how to implement this feature if required

[henon]

OK, sorry @Yomodo nevermind what I said above, selection should select children and vice versa. There is a bug in there, I can reproduce it. Whether it happens, depends on whether or not the parent was selected.

[henon]

OK, flip-flopping back to the original statement, it isn't a bug, it is just very confusing that's all. The thing causing the confusion in this example is the fact that a directory has its own selected state which does not depend on the selection of its children. So when the parent is checked off, and you check all children, then the parent will remain unchecked for TriState=false

and indeterminate for TriState=true

When the parent is checked and children are not all checked: TriState=false

When the parent is checked and children are not all checked: TriState=true

This behavior is intended but I realize it isn't very consistent. Checking the parent automatically checks all children but unchecking a child doesn't update the parent state. I will change it. Then I guess we don't need the custom logic example any longer as the treeview will behave like it automatically.

[Yomodo]

Thank you for explaining; it all makes sense now.

[henon]

I implemented the expected change in behavior so that checking/unchecking children updates the parent.

And I removed the custom checkbox example as it makes no sense any longer.

[henon]

Just note that modifying the selection via SelectedValues does not trigger any hierarchic selection like when you click the checkboxes. So for instance, if you select only bundle.zip in the chipset and leave everything else off, it will not cause all subtrees to become selected. I hope that is ok.

[henon]

@Yomodo: see PR #8957

[Yomodo]

Yes, with correct use of the TriState property, it's now exactly as (I) expected. Thanks so much!