Adornments: Enable SubViews in Margin, Border, and Padding

[tig]

This is a sub-issue of:

• Finish Adornments (master Issue)  #2994

Todo

• What happens when Adornment.Add is called? Fixed in Fixes #3273. Updates FindDeepestView to support Adornment #3278
  • Nothing special happens, but the various layout and draw methods now do the right thing.
  • The thickness is not automatically adjusted.
• How should MouseEvents work? Fixed in Fixes #3273. Updates FindDeepestView to support Adornment #3278
• How should Focus work? Because Padding is in a different view hierarchy from the dialog, Tab etc... doesn't tab into the buttons.
  • Padding - Any views added to Padding are included in Padding.Parent's focus chain. If View.Subviews[^1].HasFocus and the user presses Tab Padding.SubViews[0] will get focus. Etc...
  • Border - Ctrl-F10 is used to set focus on Border.Subviews[0]. Subsequent Tab presses cycle through Border.Subviews. Ctrl-F10 again returns focus to Border.Parent.
  • Margin - No default behavior. If someone adds views to Margin they are on their own to figure out a focus model (I can't think of any use case where it makes sense to add a subview to Margin.

Background

• Examples of SubViews in Adornments:

  • A TitleBar renders the View's Title and a horizontal line defining the top of the View. Added to Border.
    • One or more LineViews that render the View's 'Border`
  • A Vertical Scrollbar adds thickness to Padding.Right (or .Left when right-to-left language support is added).
  • A Horizontal Scrollbar adds thickness to Padding.Bottom when enabled.
  • A MenuBar adds thickness to Padding.Top (NOTE: This is a change from v1 where subview.Y = 1 is required).
  • A StatusBar adds thickness ot Padding.Bottom and is rendered at the bottom of Padding.
  • In Dialog (and derived classes), the buttons can be added to Padding (Y = Pos.AnchorEnd(1)).

• Should expanding of, e.g. Padding.Thickness be automatic when Padding.Add is called? If Dim.Auto is implemented, it might be possible for this to happen. For now: I suggest devs adding adornments manually expand thickness as appropriate. In my Dialog prototype, I did this:

		public void AddButton (Button button)
		{
			if (button == null) {
				return;
			}
			
			_buttons.Add (button);
			Padding.Thickness = new Thickness (Padding.Thickness.Top, Padding.Thickness.Left, Padding.Thickness.Right, 1);
			Padding.Add (button);
			LayoutButtons ();
		}

[BDisp]

How you think on handling the StatusBar and a ScrollBar on Padding? If a StatusBar exists then the ScrollBar should be above, right?
The MouseEvent should be handled in the same way as the KeyEvent by using the the Parent property. The FindDeepestView must be changed to look in the parent too if a null is returned.

[tig]

How you think on handling the StatusBar and a ScrollBar on Padding? If a StatusBar exists then the ScrollBar should be above, right?

Yes, I think that's right.

This reminds me of something else I was thinking about:

Thickness needs rules around which edges have precedence, by default.

E.g. which is more true, given view.Padding.Thickness = new Thickness(1); view.Width = 10; view.Height = 10;:

• Padding.Top.Width == 10 and Padding.Left.Height == 10
  OR
• Padding.Top.Width == 10 and Padding.Left.Height == 8

Note, I do NOT mean Padding.Left.Height should be different if Padding.Top/Bottom > 0 literally; just to illustrate something that could be very confusing.

Regardless, here's how I think we'd lay out a View with all four adornments:

Padding.Thickness = new Thickness (
  _menuBar.Visible ? 1 : 0,    // Top
  0,  // Left
  _verticalScrollBar.Visible ? 1: 0,  // Right
  (_statusBar.Visible ? 1 : 0) + (_horizontalScrollBar.Visible ? 1 :0));  // Bottom

// These have all been `Padding.Add()`ed
_menuBar.X = 0;
_menuBar.Y = 0;
_menuBar.Width = Dim.Fill();
_menuBar.Height = 1;

_statusBar.X = 0;
_statusBar.Y = Pos.AnchorEnd (1);
_statusBar.Width = Dim.Fill();
_statusBar.Height = 1;

_verticalScrollbar.X = Pos.AnchorEnd(1);
_verticalScrollbar.Y = _menuBar.Visible ? Pos.Bottom (_menuBar) : 0;
_verticalScrollbar.Width = 1;
_verticalScrollbar.Height = Dim.Fill ((_menuBar.Visible ? 1 : 0) + (_statusBar.Visible ? 1 : 0) + (_horizontalScrollBar.Visible ? 1 : 0));

_horizontalScrollbar.X = 0;
_horizontalcrollbar.Y = Pos.AnchorEnd (_statusBar.Visible ? 2 : 1);
_horizontalScrollbar.Width = Dim.Fill ();
_horizontalScrollbar.Height = 1;

[BDisp]

• In Dialog (and derived classes), the buttons can be added to Padding (Y = Pos.AnchorEnd(1)).

And in the cases where we want buttons arbitrary on others locations, that possible, right? Added to Padding you only mean the ones that are passed by the params, right?

[tig]

• In Dialog (and derived classes), the buttons can be added to Padding (Y = Pos.AnchorEnd(1)).

And in the cases where we want buttons arbitrary on others locations, that possible, right? Added to Padding you only mean the ones that are passed by the params, right?

Correct.

On the same note, for Wizard I plan on putting the HelpText view (a TextView that is set to readonly) in Padding:

Padding.Thickness = new Thickness (Padding.Thickness.Top, Padding.Thickness.Left, Padding.Thickness.Right, 1);
_helpText.X = Pos.AnchorEnd (1);
_helpText.Y = 0;
_helpText.Width = 15; 
_helpText.Height = Dim.Fill (2); // +1 for buttons on Bottom
Padding.Add (_helpText);

[tig]

A key part of addressing this issue will be:

• enable Margin, Border, Padding to be overridden/replaced by a View derivative

Less important (and highly debatlve), but interesting. Including this just to make sure we are intentional:

• enable Margin, Border, Padding to be overriden/replaced by a user of a View.

[BDisp]

A key part of addressing this issue will be:

• enable Margin, Border, Padding to be overridden/replaced by a View derivative

Less important (and highly debatlve), but interesting. Including this just to make sure we are intentional:

• enable Margin, Border, Padding to be overriden/replaced by a user of a View.

Just to remember that you may want to join LineCanvas through a View (Margin, Border, Padding) but not with others views.

[tig]

A key part of addressing this issue will be:

• enable Margin, Border, Padding to be overridden/replaced by a View derivative

Less important (and highly debatlve), but interesting. Including this just to make sure we are intentional:

• enable Margin, Border, Padding to be overriden/replaced by a user of a View.

Just to remember that you may want to join LineCanvas through a View (Margin, Border, Padding) but not with others views.

If I understand you correctly, this is what SuperViewRendersLineCanvas is for.