Feat/focus layout (workspacer#276)

* feat : add Focus Layout

* feat: organized focus layout to open new windows on the bottom right

* removed comment typo

* chore: refactor to extract some calculation from CalcLayout

* fix: bug when more than one primary, added unit tests, main area fill screen when no secondary

Co-authored-by: Benoit Lalande <blalande@d-edge.com>
Co-authored-by: Jostein Kjønigsen <jostein@kjonigsen.net>

src/workspacer.Shared.Tests/FocusLayoutTest.cs

@@ -0,0 +1,23 @@
+using Xunit;
+
+namespace workspacer.Shared.Tests
+{
+    public class FocusLayoutTest
+    {
+        [Theory]
+        [InlineData(5, 2, 2, 1)]
+        [InlineData(6, 2, 2, 2)]
+        [InlineData(5, 1, 2, 2)]
+        [InlineData(4, 1, 2, 1)]
+        [InlineData(2, 1, 1, 0)]
+        [InlineData(1, 1, 0, 0)]
+        [InlineData(2, 2, 0, 0)]
+        [InlineData(3, 2, 1, 0)]
+        public void CheckNumberWindows(int numWindows, int numInPrimary, int expectedLeft, int expectedRight)
+        {
+            FocusLayoutEngine focusLayoutEngine = new FocusLayoutEngine();
+            Assert.Equal(expectedLeft, focusLayoutEngine.GetNbLeftWindows(numWindows, numInPrimary));
+            Assert.Equal(expectedRight, focusLayoutEngine.GetNbRightWindows(numWindows, numInPrimary));
+        }
+    }
+}

src/workspacer.Shared/Layout/FocusLayoutEngine.cs

@@ -0,0 +1,139 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace workspacer
+{
+    // a layout that put the master view in the center of the screen, and the secondary windows on both sides, new windows opening on the right side
+    public class FocusLayoutEngine : ILayoutEngine
+    {
+        public string Name => "focus";
+
+        private readonly int _numInPrimary;
+        private readonly double _primaryPercent;
+        private readonly double _primaryPercentIncrement;
+
+        private int _numInPrimaryOffset = 0;
+        private double _primaryPercentOffset = 0;
+
+
+        public FocusLayoutEngine() : this(1, 0.7, 0.03) { }
+
+        public FocusLayoutEngine(int numInPrimary, double primaryPercent, double primaryPercentIncrement)
+        {
+            _numInPrimary = numInPrimary;
+            _primaryPercent = primaryPercent;
+            _primaryPercentIncrement = primaryPercentIncrement;
+
+        }
+
+        public IEnumerable<IWindowLocation> CalcLayout(IEnumerable<IWindow> windows, int spaceWidth, int spaceHeight)
+        {
+            var list = new List<IWindowLocation>();
+            var numWindows = windows.Count();
+
+            if (numWindows == 0)
+                return list;
+
+            int numInPrimary = Math.Min(GetNumInPrimary(), numWindows);
+            int nbLeftWindows = GetNbLeftWindows(numWindows, numInPrimary);
+            int nbRightWindows = GetNbRightWindows(numWindows, numInPrimary);
+
+            int primaryWidth = (int)(spaceWidth * (_primaryPercent + _primaryPercentOffset));
+            int secondaryWidth = (spaceWidth - primaryWidth) / 2;
+
+            int primaryHeight = spaceHeight / numInPrimary;
+            int leftHeight = GetSecondaryHeight(spaceHeight, nbLeftWindows);
+            int rightHeight = GetSecondaryHeight(spaceHeight, nbRightWindows);
+
+
+            // if there are more "primary" windows than actual windows,
+            // then we want the pane to actually spread the entire width
+            // of the working area
+            if (numInPrimary >= numWindows)
+            {
+                primaryWidth = spaceWidth;
+                secondaryWidth = 0;
+            }
+            else if (nbRightWindows == 0)
+            {
+                // fill up the right side if no windows
+                primaryWidth += secondaryWidth;
+            }
+
+
+            for (var i = 0; i < numWindows; i++)
+            {
+                if (i < numInPrimary)
+                {
+                    list.Add(new WindowLocation(secondaryWidth, i * primaryHeight, primaryWidth, primaryHeight, WindowState.Normal));
+                }
+                else
+                {
+                    if (i < nbLeftWindows + numInPrimary)
+                    {
+                        // left side
+                        list.Add(new WindowLocation(0, (i - numInPrimary) * leftHeight, secondaryWidth, leftHeight, WindowState.Normal));
+                    }
+                    else
+                    {
+                        // right side
+                        list.Add(new WindowLocation(secondaryWidth + primaryWidth, (i - numInPrimary - nbLeftWindows) * rightHeight, secondaryWidth, rightHeight, WindowState.Normal));
+                    }
+                }
+            }
+            return list;
+        }
+
+        public int GetNbLeftWindows(int numWindows, int numInPrimary)
+        {
+            // +1 so that we round up
+            return (numWindows - numInPrimary + 1) / 2;
+        }
+
+        public int GetNbRightWindows(int numWindows, int numInPrimary)
+        {
+            return (numWindows - numInPrimary) / 2; // rounded down
+        }
+
+        public int GetSecondaryHeight(int spaceHeight, int nbWindows)
+        {
+            return spaceHeight / Math.Max(nbWindows, 1);
+        }
+
+
+        public void ShrinkPrimaryArea()
+        {
+            _primaryPercentOffset -= _primaryPercentIncrement;
+        }
+
+        public void ExpandPrimaryArea()
+        {
+            _primaryPercentOffset += _primaryPercentIncrement;
+        }
+
+        public void ResetPrimaryArea()
+        {
+            _primaryPercentOffset = 0;
+        }
+
+        public void IncrementNumInPrimary()
+        {
+            _numInPrimaryOffset++;
+        }
+
+        public void DecrementNumInPrimary()
+        {
+            if (GetNumInPrimary() > 1)
+            {
+                _numInPrimaryOffset--;
+            }
+        }
+
+        private int GetNumInPrimary()
+        {
+            return _numInPrimary + _numInPrimaryOffset;
+        }
+
+    }
+}