First grid splitter implementation

src/Perspex.Controls/GridSplitter.cs

@@ -2,42 +2,152 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using Perspex.Controls.Primitives;
 using Perspex.Input;
-using Perspex.Rendering;
 using Perspex.VisualTree;
 
 namespace Perspex.Controls
 {
+    /// <summary>
+    /// Unlike WPF GridSplitter, Perspex GridSplitter has only one Behavior. It's GridResizeBehavior.PreviousAndNext
+    /// </summary>
     public class GridSplitter : Thumb
     {
         private Grid _grid;
 
+        private DefinitionBase _prevDefinition;
+
+        private DefinitionBase _nextDefinition;
+
+        private bool _isResizingColumns;
+
+        private List<DefinitionBase> _definitions;
+
         /// <summary>
-        /// Initializes a new instance of the <see cref="GridSplitter"/> class.
+        /// Decide depending on set size
         /// </summary>
-        public GridSplitter()
+        /// <returns></returns>
+        private bool IsResizingColumns()
+        {
+            if (!double.IsNaN(Width))
+            {
+                return true;
+            }
+            if (!double.IsNaN(Height))
+            {
+                return false;
+            }
+            throw new InvalidOperationException("GridSpliter Should have width or height set. It affects whether columns or rows it resizes");
+        }
+
+        private double GetActualLength(DefinitionBase definition)
         {
-            Cursor = new Cursor(StandardCursorType.SizeWestEast);
+            var columnDefinition = definition as ColumnDefinition;
+            return columnDefinition?.ActualWidth ?? ((RowDefinition)definition).ActualHeight;
         }
 
+        private double GetMinLength(DefinitionBase definition)
+        {
+            var columnDefinition = definition as ColumnDefinition;
+            return columnDefinition?.MinWidth ?? ((RowDefinition)definition).MinHeight;
+        }
+
+        private double GetMaxLength(DefinitionBase definition)
+        {
+            var columnDefinition = definition as ColumnDefinition;
+            return columnDefinition?.MaxWidth ?? ((RowDefinition)definition).MaxHeight;
+        }
+
+        private bool IsStar(DefinitionBase definition)
+        {
+            var columnDefinition = definition as ColumnDefinition;
+            return columnDefinition?.Width.IsStar ?? ((RowDefinition)definition).Height.IsStar;
+        }
+
+        private void SetLengthInStars(DefinitionBase definition, double value)
+        {
+            var columnDefinition = definition as ColumnDefinition;
+            if (columnDefinition != null)
+            {
+                columnDefinition.Width = new GridLength(value, GridUnitType.Star);
+            }
+            else
+            {
+                ((RowDefinition)definition).Height = new GridLength(value, GridUnitType.Star);
+            }
+        }
+
+
+
+
+        private void GetDeltaConstraints(out double min, out double max)
+        {
+            double prevDefinitionLen = GetActualLength(_prevDefinition);
+            double prevDefinitionMin = GetMinLength(_prevDefinition);
+            double prevDefinitionMax = GetMaxLength(_prevDefinition);
+
+            double nextDefinitionLen = GetActualLength(_nextDefinition);
+            double nextDefinitionMin = GetMinLength(_nextDefinition);
+            double nextDefinitionMax = GetMaxLength(_nextDefinition);
+
+
+            // Determine the minimum and maximum the columns can be resized
+            min = -Math.Min(prevDefinitionLen - prevDefinitionMin, nextDefinitionMax - nextDefinitionLen);
+            max = Math.Min(prevDefinitionMax - prevDefinitionLen, nextDefinitionLen - nextDefinitionMin);
+        }
+
+
         protected override void OnDragDelta(VectorEventArgs e)
         {
-            int col = GetValue(Grid.ColumnProperty);
+            var delta = _isResizingColumns  ? e.Vector.X : e.Vector.Y;
+
+            double max;
+            double min;
+            GetDeltaConstraints(out min, out max);
+            delta = Math.Min(Math.Max(delta, min), max);
 
-            if (_grid != null && col > 0)
+
+            foreach (var definition in _definitions)
             {
-                var size = _grid.ColumnDefinitions[col - 1].ActualWidth + e.Vector.X;               
-                _grid.ColumnDefinitions[col - 1].Width = new GridLength(
-                    Math.Max(0, size),
-                    GridUnitType.Pixel);
+                if (definition == _prevDefinition)
+                {
+                    SetLengthInStars(_prevDefinition, GetActualLength(_prevDefinition) + delta);
+                }
+                else if (definition == _nextDefinition)
+                {
+                    SetLengthInStars(_nextDefinition, GetActualLength(_nextDefinition) - delta);
+                }
+                else if(IsStar(definition))
+                {
+                    SetLengthInStars(definition, GetActualLength(definition)); // same size but in stars
+                }
             }
         }
 
         protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
         {
+            //new Range
             base.OnAttachedToVisualTree(e);
             _grid = this.GetVisualParent<Grid>();
+            _isResizingColumns = IsResizingColumns();
+            if (_isResizingColumns)
+            {
+                Cursor = new Cursor(StandardCursorType.SizeWestEast);
+                var col = GetValue(Grid.ColumnProperty);
+                _definitions = _grid.ColumnDefinitions.Cast<DefinitionBase>().ToList();
+                _prevDefinition = _definitions[col - 1];
+                _nextDefinition = _definitions[col + 1];
+            }
+            else
+            {
+                Cursor = new Cursor(StandardCursorType.SizeNorthSouth);
+                var row = GetValue(Grid.RowProperty);
+                _definitions = _grid.RowDefinitions.Cast<DefinitionBase>().ToList();
+                _prevDefinition = _definitions[row - 1];
+                _nextDefinition = _definitions[row + 1];
+            }
         }
     }
 }