`TableView` - Upgrade to use Content Area for scrolling

[tig]

Once #3820 is done, which fixes

• Create new ScrollBar based on a new Scroll and remove ScrollBarView/ScrollView #2489

we will want to upgrade TableView to support ScrollBar. There are two approaches:

1. Upgrade TableView to utilize the virtual content scrolling now built into View via Viewport, ViewportSettings, and SetContentSize().
2. Leave the existing scroll logic in place, and program View.HorizontalScrollBar/VerticalScrollBar manually.

The former is a far better solution and should not be too hard to accomplish.

[tznind]

TableView horizontal scrolling is by table column not characters. Does the new ScrollBar support 'virtual' viewport units which do not have to match directly to runes?

One of the core principles for TableView is not having to calculate the content area. Instead it lays out content starting at the current row/col offset until it runs out of screen space. This is done for performance - in order to support basically unlimited table sizes (e.g. for CSV browsing or other use cases).

[tig]

TableView horizontal scrolling is by table column not characters. Does the new ScrollBar support 'virtual' viewport units which do not have to match directly to runes?

Yep!

See how CharMap does it (where each column is 3 wide).

One of the core principles for TableView is not having to calculate the content area. Instead it lays out content starting at the current row/col offset until it runs out of screen space. This is done for performance - in order to support basically unlimited table sizes (e.g. for CSV browsing or other use cases).

Not a problem.

Initialy call SetContentSize with a height +1.

Whenever a row is added or the Viewport changes because the user has scrolled one past the end, just call SetContentSize() with a Height++.

[tig]

Or, just do 2).

However, I'm quite confident if you do 1) you'll end up removing a TON of code from the class...

[tig]

Oh, and I just added this to ViewportSettings. Previously you wouldn't need to set this for what Tableview wants, but now you'll have to.

    /// <summary>
    ///     If set and <see cref="View.Viewport"/><c>.Width</c> is greater than <see cref="View.GetContentSize ()"/>
    ///     <c>.Width</c> <see cref="View.Viewport"/><c>.X</c> can be negative.
    ///     <para>
    ///         When not set, <see cref="View.Viewport"/><c>.X</c> will be constrained to non-negative values when
    ///         <see cref="View.Viewport"/><c>.Width</c> is greater than <see cref="View.GetContentSize ()"/>
    ///         <c>.Width</c>, preventing
    ///         scrolling beyond the left of the Viewport.
    ///     </para>
    ///     <para>
    ///         This can be useful in infinite scrolling scenarios.
    ///     </para>
    /// </summary>
    AllowNegativeXWhenWidthGreaterThanContentWidth = 16,

    /// <summary>
    ///     If set and <see cref="View.Viewport"/><c>.Height</c> is greater than <see cref="View.GetContentSize ()"/>
    ///     <c>.Height</c> <see cref="View.Viewport"/><c>.Y</c> can be negative.
    ///     <para>
    ///         When not set, <see cref="View.Viewport"/><c>.Y</c> will be constrained to non-negative values when
    ///         <see cref="View.Viewport"/><c>.Height</c> is greater than <see cref="View.GetContentSize ()"/>
    ///         <c>.Height</c>, preventing
    ///         scrolling above the top of the Viewport.
    ///     </para>
    ///     <para>
    ///         This can be useful in infinite scrolling scenarios.
    ///     </para>
    /// </summary>
    AllowNegativeYWhenHeightGreaterThanContentHeight = 32,

The reason I disabled this behavior by default is most use-cases do not want scrolling way beyond content.