replace v6 with experimental v7 code

src/MpvNet.Windows/WinForms/SnapManager.cs

@@ -0,0 +1,80 @@
+
+using System.Drawing;
+using System.Runtime.InteropServices;
+using System.Windows.Forms;
+using MpvNet.Windows.Native;
+
+using static MpvNet.Windows.Native.WinApi;
+
+namespace MpvNet.Windows.WinForms;
+
+public class SnapManager
+{
+    int DragOffsetX { get; set; }
+    int DragOffsetY { get; set; }
+
+    IntPtr Handle;
+
+    [Flags]
+    public enum SnapLocation
+    {
+        None   = 0,
+        Left   = 1 << 0,
+        Top    = 1 << 1,
+        Right  = 1 << 2,
+        Bottom = 1 << 3,
+        All = Left | Top | Right | Bottom
+    }
+
+    public int AnchorDistance { get; set; }
+
+    public int SnapDistance { get; set; }
+
+    bool InSnapRange(int a, int b) => Math.Abs(a - b) < SnapDistance;
+
+    void FindSnap(ref Rectangle effectiveBounds)
+    {
+        Screen currentScreen = Screen.FromPoint(effectiveBounds.Location);
+        Rectangle workingArea = GetWorkingArea(Handle, currentScreen.WorkingArea);
+
+        if (InSnapRange(effectiveBounds.Left, workingArea.Left + AnchorDistance))
+            effectiveBounds.X = workingArea.Left + AnchorDistance;
+        else if (InSnapRange(effectiveBounds.Right, workingArea.Right - AnchorDistance))
+            effectiveBounds.X = workingArea.Right - AnchorDistance - effectiveBounds.Width;
+        if (InSnapRange(effectiveBounds.Top, workingArea.Top + AnchorDistance))
+            effectiveBounds.Y = workingArea.Top + AnchorDistance;
+        else if (InSnapRange(effectiveBounds.Bottom, workingArea.Bottom - AnchorDistance))
+            effectiveBounds.Y = workingArea.Bottom - AnchorDistance - effectiveBounds.Height;
+    }
+
+    public void OnMoving(ref Message m)
+    {
+        if (Handle == IntPtr.Zero)
+            return;
+
+        WinApi.Rect boundsLtrb = Marshal.PtrToStructure<WinApi.Rect>(m.LParam);
+        Rectangle bounds = boundsLtrb.ToRectangle();
+        // This is where the window _would_ be located if snapping
+        // had not occurred. This prevents the cursor from sliding
+        // off the title bar if the snap distance is too large.
+        Rectangle effectiveBounds = new Rectangle(
+            Cursor.Position.X - DragOffsetX,
+            Cursor.Position.Y - DragOffsetY,
+            bounds.Width,
+            bounds.Height);
+        FindSnap(ref effectiveBounds);
+        WinApi.Rect newLtrb = WinApi.Rect.FromRectangle(effectiveBounds);
+        Marshal.StructureToPtr(newLtrb, m.LParam, false);
+        m.Result = new IntPtr(1);
+    }
+
+    public void OnSizeAndEnterSizeMove(Form form)
+    {
+        Handle = form.Handle;
+        SnapDistance = form.Font.Height;
+        // Need to handle window size changed as well when
+        // un-maximizing the form by dragging the title bar.
+        DragOffsetX = Cursor.Position.X - form.Left;
+        DragOffsetY = Cursor.Position.Y - form.Top;
+    }
+}