From 4dbc0aabc780b846b24bf25600d45a953d78855e Mon Sep 17 00:00:00 2001
From: Jonathan Jenne <j.jenne@digitaldata.works>
Date: Thu, 23 Sep 2021 11:04:31 +0200
Subject: [PATCH] Windows/Window: Add SnapToBorder

---
 Windows/Window.vb | 87 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)

diff --git a/Windows/Window.vb b/Windows/Window.vb
index 08932317..1d390fb2 100644
--- a/Windows/Window.vb
+++ b/Windows/Window.vb
@@ -7,6 +7,8 @@ Imports DigitalData.Modules.Logging
 Public Class Window
     Private _Logger As Logger
 
+    Private Const WINDOW_SNAP_OFFSET = 35
+
     Public Enum Anchor
         TopLeft
         BottomLeft
@@ -387,4 +389,89 @@ Public Class Window
             Throw ex
         End Try
     End Function
+
+    <StructLayout(LayoutKind.Sequential)>
+    Public Structure WINDOWPOS
+        Public hwnd As IntPtr
+        Public hwndInsertAfter As IntPtr
+        Public x As Integer
+        Public y As Integer
+        Public cx As Integer
+        Public cy As Integer
+        Public flags As Integer
+    End Structure
+
+    Public Shared Sub SnapToDesktopBorder(pForm As Form, pLParam As IntPtr, Optional pWidthAdjustment As Integer = 0)
+        If pForm Is Nothing Then
+            ' Satisfies rule: Validate parameters
+            Throw New ArgumentNullException("pForm")
+        End If
+
+        ' Snap client to the top, left, bottom or right desktop border
+        ' as the form is moved near that border
+        Try
+            ' Marshal the LPARAM value which is a WINDOWPOS struct
+            Dim oNewPosition As New WINDOWPOS
+            oNewPosition = CType(Marshal.PtrToStructure(pLParam, GetType(WINDOWPOS)), WINDOWPOS)
+
+            If oNewPosition.y = 0 OrElse oNewPosition.x = 0 Then
+                Return ' Nothing to do!
+            End If
+
+            ' Adjust the client size for borders and caption bar
+            Dim oClientRect As Rectangle = pForm.RectangleToScreen(pForm.ClientRectangle)
+            oClientRect.Width += SystemInformation.FrameBorderSize.Width - pWidthAdjustment
+            oClientRect.Height += (SystemInformation.FrameBorderSize.Height + SystemInformation.CaptionHeight)
+
+            ' Now get the screen working area (without taskbar)
+            Dim oWorkingRect As Rectangle = System.Windows.Forms.Screen.GetWorkingArea(pForm.ClientRectangle)
+
+            ' Left border
+            If oNewPosition.x >= oWorkingRect.X - WINDOW_SNAP_OFFSET AndAlso
+                oNewPosition.x <= oWorkingRect.X + WINDOW_SNAP_OFFSET Then
+                oNewPosition.x = oWorkingRect.X
+            End If
+
+            ' Get screen bounds and taskbar height
+            ' (when taskbar is horizontal)
+            Dim oScreenRect As Rectangle = System.Windows.Forms.Screen.GetBounds(System.Windows.Forms.Screen.PrimaryScreen.Bounds)
+            Dim oTaskbarHeight As Integer = oScreenRect.Height - oWorkingRect.Height
+
+            ' Top border (check if taskbar is on top
+            ' or bottom via WorkingRect.Y)
+            If oNewPosition.y >= -WINDOW_SNAP_OFFSET AndAlso
+                 (oWorkingRect.Y > 0 AndAlso oNewPosition.y <=
+                 (oTaskbarHeight + WINDOW_SNAP_OFFSET)) OrElse
+                 (oWorkingRect.Y <= 0 AndAlso oNewPosition.y <=
+                 (WINDOW_SNAP_OFFSET)) Then
+                If oTaskbarHeight > 0 Then
+                    oNewPosition.y = oWorkingRect.Y ' Horizontal Taskbar
+                Else
+                    oNewPosition.y = 0 ' Vertical Taskbar
+                End If
+            End If
+
+            ' Right border
+            If oNewPosition.x + oClientRect.Width <=
+                 oWorkingRect.Right + WINDOW_SNAP_OFFSET AndAlso
+                 oNewPosition.x + oClientRect.Width >=
+                 oWorkingRect.Right - WINDOW_SNAP_OFFSET Then
+                oNewPosition.x = oWorkingRect.Right - (oClientRect.Width +
+                                SystemInformation.FrameBorderSize.Width)
+            End If
+
+            ' Bottom border
+            If oNewPosition.y + oClientRect.Height <=
+                   oWorkingRect.Bottom + WINDOW_SNAP_OFFSET AndAlso
+                   oNewPosition.y + oClientRect.Height >=
+                   oWorkingRect.Bottom - WINDOW_SNAP_OFFSET Then
+                oNewPosition.y = oWorkingRect.Bottom - (oClientRect.Height +
+                                SystemInformation.FrameBorderSize.Height)
+            End If
+
+            ' Marshal it back
+            Marshal.StructureToPtr(oNewPosition, pLParam, True)
+        Catch ex As ArgumentException
+        End Try
+    End Sub
 End Class