GridSplitter adding width to column will make grid overflow

[fatcatz888]

I'm submitting a...

Current behavior

Adjusting the splitter when the second column has a default width will make the grid overflow when dragged right then left.

Expected behavior

Splitter respects the root grid bounds.

Minimal reproduction of the problem with instructions

Using GridSplitter in UWP Community Toolkit Sample App.
Change line 19 and 20 to:

<ColumnDefinition Width="120" />
<ColumnDefinition MinWidth="100" />

Drag vertical splitter right then left. It will allow you to resize the second column all the way to the right edge of the widow hiding the third column.

Environment

Nuget Package(s): 
Microsoft.Toolkit v2.2.0
Microsoft.Toolkit.Uwp v2.2.0
Microsoft.Toolkit.Uwp v2.2.0
Microsoft.Toolkit.Uwp.Controls v2.2.0

Package Version(s): 

Windows 10 Build Number:
- [ ] Anniversary Update (14393) 
- [ ] Creators Update (15063)
- [X ] Fall Creators Update (16299)
- [ ] Insider Build (build number: )

App min and target version:
- [ ] Anniversary Update (14393) 
- [ ] Creators Update (15063)
- [X ] Fall Creators Update (16299)
- [ ] Insider Build (xxxxx)

Device form factor:
- [ X] Desktop
- [ ] Mobile
- [ ] Xbox
- [ ] Surface Hub
- [ ] IoT

Visual Studio 
- [X ] 2017 (version: 15.6.1)
- [ ] 2017 Preview (version: )

[skendrot]

We need to figure out a way to unit test that thing...

[windowstoolkitbot]

This issue seems inactive. It will automatically be closed in 14 days if there is no activity.

[kbrons]

I'm going to work on this, if that's OK.

[fatcatz888]

Please do. It might also be affecting the cursor too as sometimes when I navigate to a page with the GridSplitter controls the cursor disappears. It only appears when the cursor is hovering over the GridSplitter control.

[kbrons]

I'm not sure if that's related to this issue. Would you mind just reporting it as a separate issue? If I'm wrong, I'll also reference the second issue in the pull request.

[fatcatz888]

Ok, I'll report it as a separate issue.