Grid: Provide information for the actual height of RowDefinition and actual width of ColumnDefinition

[eli-popova]

Description

Currently, we can set the Height property of a RowDefinition object and the Width property of a ColumnDefinition object with some value and a unit type of Absolute, Star and Auto. What we need, however, is to have information about the real sizes of rows/columns in the grid after it has been measured. In WinUI and WPF we have a public API providing such information. It would be great if we had this in MAUI as well.

Public API Changes

public sealed class RowDefinition
{
   ...
   public double ActualHeight { get; private set; }   ---> the calculated height of the row after the grid has been measured and arranged
   ...
}

public sealed class ColumnDefinition
{
    ...
    public double ActualWidth { get; private set;}    ---> the calculated width of the column after the grid has been measured and arranged
    ...
}

Intended Use-Case

We need this information as we are developing a GridSplitter control. To resize rows/columns by dragging the splitter we need to know their exact sizes.

[maxiptah]

Same problem here. I needed this control just for my own application and I came up with this partial workaround: if in the containing grid your rows are all measured absolutely or in stars, you can calculate the actual row height by substracting all absolute heights of other rows and dividing the remaining space by the remaining number of stars. Works for me, but will break with "Auto" sized rows..

   private double GetActualRowHeight(Grid grid, int rowIndex)
   {
       var height = grid.RowDefinitions[rowIndex].Height;
       if (height.IsAbsolute)
       {
           return height.Value;
       }

      if (height.IsAuto) 
     {
           throw new NotImplementedException();
     }

       var totalStars = 0;
       var remainingHeight = grid.Height;
       foreach (var rowDefinition in grid.RowDefinitions)
       {
           if (rowDefinition.Height.IsAbsolute)
           {
               remainingHeight -= rowDefinition.Height.Value;
           }
           else if (rowDefinition.Height.IsStar)
           {
               totalStars += (int)rowDefinition.Height.Value;
           }
           else if (row definition.Height.IsAuto)
           {
              throw new NotImplementedException();
              // Need to calculate based on children, which I'm not sure is reliably possible
           }
       }

       return totalStars > 0
           ? remainingHeight / totalStars
           : remainingHeight;
   }