Tuple Notation to enable Complete Column/Row Definitions

[najak3d]

Perhaps there is already a notation for this, but in the code, I didn't find it.

The issue I see is that when Grids are inside containers of variable (or unknown sizes), it's OFTEN needed to specify the "MinWidth" to prevent the most important cells from becoming unusable. The current syntax/parsing only allow for parsing the "Width" GridLength. (or Height for Row Definitions).

I think Avalonia should support "tuple-notation" for this, such as:

ColumnDefinitions = "2, (30*, 400), 2, (15*, 250, 400), (2), 55*, 2"

where:
"(30*, 400)" means "Width = "30*" and "MinWidth = 400"
"(15*, 250, 400)" means "Width = "15*", MinWidth = 250, MaxWidth = 400
"(2)" simply means "Width=2" just to be consistent, and support 1-Tuples.

I have already re-written the parsing logic for these Strings, which is working out dandy for me, using the new "Markup.Declarative" library.

private static IEnumerable<ColumnDefinition> _ParseColumnsDef(string s)
{
  int tupleIndex = 0;
  (GridLength width, double min, double max) def = (new GridLength(), 0, 0);
  
  using (var tokenizer = new Avalonia.Utilities.StringTokenizer(s, System.Globalization.CultureInfo.InvariantCulture))
  {
	  while (tokenizer.TryReadString(out var item))
	  {
		  if (tupleIndex > 0)
		  {   // Look for ending bracket
			  bool isTerminated = item.EndsWith(')');
			  if (isTerminated)
				  item = item.Substring(0, item.Length - 1);
  
			  if (tupleIndex == 1)
				  def.min = double.Parse(item);
			  else
				  def.max = double.Parse(item);
  
			  tupleIndex++;
  
			  if (isTerminated)
			  {
				  if (tupleIndex > 3) throw new FormatException($"Cols() extension, Bad Formatting of definitions: {s}");
  
				  if (tupleIndex == 2)
					  yield return new ColumnDefinition(def.width) { MinWidth = def.min };
				  else
					  yield return new ColumnDefinition(def.width) { MinWidth = def.min, MaxWidth = def.max };
  
				  tupleIndex = 0; // reset
			  }
		  }
		  else
		  {	// Not Tuple yet -- looking for start of Tuple, or a simple GridLength Width definition
			  if (item.StartsWith('('))
			  {   // It's a Tuple, more complete definition of ColumnDefition:  (Width, Min, [optional:Max])
				  if (item.EndsWith(')'))
				  {	// it's a 1-tuple... so treat the same as a non-tuple, after strippig the '()'
					  item = item.Substring(1, item.Length - 2);
				  }
				  else
				  {	// it's the beginning of a tuple
					  def.width = GridLength.Parse(item.Substring(1));
					  tupleIndex = 1;
					  continue; // done, do not yield, we are processing a tuple now
				  }
			  }
			  // Simple definition for Width property only
			  yield return new ColumnDefinition(GridLength.Parse(item));
		  }
	  }
  }
  if (tupleIndex != 0) throw new FormatException($"Cols() extension, Bad Formatting of definitions, Tuple-not-terminated: {s}");
}

[najak3d]

This relates to a new issue I filed against Markup.Declarative, requesting that we provide our own parsing logic (shown above) to enable this tuple-notation.

AvaloniaUI/Avalonia.Markup.Declarative#16

But it would be BETTER if Avalonia simply supported this notation natively (with code I provided), and we could just tell Avalonia to parse these tuples for us. (no custom code for us)