Show WinForm below a cell - vb.net

Question

How can I show I winform that I create in VB.NET just below the active cell?
I have no idea how to solve this. I found the following promising solutions:
Excel addin: Cell absolute position
-The accepted solution seems too complicated to work reliably. I got an error on the first row (Private Declare Function GetDC Lib "user32" (ByVal hwnd As Long) As Long)
-The second solution looked promising, but it didn't give me the right positions for my windows form.
The following adaptations of the second proposed solution does not create any errors but does not put the windows form in the correct position:
Public Sub GetScreenPositionFromCell(cell As Excel.Range, excel As Excel.Application)
Dim x As Double
Dim y As Double
If Not excel.ActiveWindow Is Nothing Then
x = excel.ActiveWindow.PointsToScreenPixelsX(cell.Left)
y = excel.ActiveWindow.PointsToScreenPixelsY(cell.Top)
End If
Me.Left = x
Me.Top = y
Me.Show()
Me.TopMost = True
End Sub
EDIT: #Loating, here is how I have used your code. It's great and I am very happy that you are taking your time to help me with a solution. The x-coordinates seems to work while the x-coordinates are a bit off and more or less off depending on the zoom level.
Public Sub ShowMeBelowActiveCell()
Dim ExcelApp As Excel.Application = CType(AddinExpress.MSO.ADXAddinModule.CurrentInstance, AddinModule).ExcelApp
Dim excelWindow = ExcelApp.ActiveWindow
Dim cell = ExcelApp.ActiveCell
Dim zoomFactor As Double = excelWindow.Zoom / 100
Dim ws = cell.Worksheet
' PointsToScreenPixels returns different values if the scroll is not currently 1
' Temporarily set the scroll back to 1 so that PointsToScreenPixels returns a
' value we know how to handle.
Dim origScrollCol = excelWindow.ScrollColumn
Dim origScrollRow = excelWindow.ScrollRow
excelWindow.ScrollColumn = 1
excelWindow.ScrollRow = 1
' (x,y) are screen coordinates for the top left corner of the top left cell
Dim x As Integer = excelWindow.PointsToScreenPixelsX(0)
' e.g. window.x + row header width
Dim y As Integer = excelWindow.PointsToScreenPixelsY(0)
' e.g. window.y + ribbon height + column headers height
Dim dpiX As Single = 0
Dim dpiY As Single = 0
Using g = Drawing.Graphics.FromHwnd(IntPtr.Zero)
dpiX = g.DpiX
dpiY = g.DpiY
End Using
' Note: Each column width / row height has to be calculated individually.
' Before, tried to use this approach:
' var r2 = (Microsoft.Office.Interop.Excel.Range) cell.Worksheet.Cells[origScrollRow, origScrollCol];
' double dw = cell.Left - r2.Left;
' double dh = cell.Top - r2.Top;
' However, that only works when the zoom factor is a whole number.
' A fractional zoom (e.g. 1.27) causes each individual row or column to round to the closest whole number,
' which means having to loop through.
For i As Integer = origScrollCol To cell.Column - 1
Dim col = DirectCast(ws.Cells(cell.Row, i), Microsoft.Office.Interop.Excel.Range)
Dim ww As Double = col.Width * dpiX / 72
Dim newW As Double = zoomFactor * ww
x += CInt(Math.Round(newW))
Next
For i As Integer = origScrollRow To cell.Row - 1
Dim row = DirectCast(ws.Cells(i, cell.Column), Microsoft.Office.Interop.Excel.Range)
Dim hh As Double = row.Height * dpiY / 72
Dim newH As Double = zoomFactor * hh
y += CInt(Math.Round(newH))
Next
excelWindow.ScrollColumn = origScrollCol
excelWindow.ScrollRow = origScrollRow
Me.StartPosition = Windows.Forms.FormStartPosition.Manual
Me.Location = New Drawing.Point(x, y)
Me.Show()
End Sub
End Class

Answer 1

When the ScrollColumn and ScrollRow are both 1, then PointsToScreenPixelsX/Y seems to return the top left point of the top left visible cell in screen coordinates. Using this, the offset width and height to the active cell is calculated, taking into consideration the zoom setting.
var excelApp = Globals.ThisAddIn.Application;
var excelWindow = excelApp.ActiveWindow;
var cell = excelApp.ActiveCell;
double zoomFactor = excelWindow.Zoom / 100;
var ws = cell.Worksheet;
var ap = excelWindow.ActivePane; // might be split panes
var origScrollCol = ap.ScrollColumn;
var origScrollRow = ap.ScrollRow;
excelApp.ScreenUpdating = false;
// when FreezePanes == true, ap.ScrollColumn/Row will only reset
// as much as the location of the frozen splitter
ap.ScrollColumn = 1;
ap.ScrollRow = 1;
// PointsToScreenPixels returns different values if the scroll is not currently 1
// Temporarily set the scroll back to 1 so that PointsToScreenPixels returns a
// value we know how to handle.
// (x,y) are screen coordinates for the top left corner of the top left cell
int x = ap.PointsToScreenPixelsX(0); // e.g. window.x + row header width
int y = ap.PointsToScreenPixelsY(0); // e.g. window.y + ribbon height + column headers height
float dpiX = 0;
float dpiY = 0;
using (var g = Graphics.FromHwnd(IntPtr.Zero)) {
dpiX = g.DpiX;
dpiY = g.DpiY;
}
int deltaRow = 0;
int deltaCol = 0;
int fromCol = origScrollCol;
int fromRow = origScrollRow;
if (excelWindow.FreezePanes) {
fromCol = 1;
fromRow = 1;
deltaCol = origScrollCol - ap.ScrollColumn; // Note: ap.ScrollColumn/Row <> 1
deltaRow = origScrollRow - ap.ScrollRow; // see comment: when FreezePanes == true ...
}
// Note: Each column width / row height has to be calculated individually.
// Before, tried to use this approach:
// var r2 = (Microsoft.Office.Interop.Excel.Range) cell.Worksheet.Cells[origScrollRow, origScrollCol];
// double dw = cell.Left - r2.Left;
// double dh = cell.Top - r2.Top;
// However, that only works when the zoom factor is a whole number.
// A fractional zoom (e.g. 1.27) causes each individual row or column to round to the closest whole number,
// which means having to loop through.
for (int i = fromCol; i < cell.Column; i++) {
// skip the columns between the frozen split and the first visible column
if (i >= ap.ScrollColumn && i < ap.ScrollColumn + deltaCol)
continue;
var col = ((Microsoft.Office.Interop.Excel.Range) ws.Cells[cell.Row, i]);
double ww = col.Width * dpiX / 72;
double newW = zoomFactor * ww;
x += (int) Math.Round(newW);
}
for (int i = fromRow; i < cell.Row; i++) {
// skip the columns between the frozen split and the first visible column
if (i >= ap.ScrollRow && i < ap.ScrollRow + deltaRow)
continue;
var row = ((Microsoft.Office.Interop.Excel.Range) ws.Cells[i, cell.Column]);
double hh = row.Height * dpiY / 72;
double newH = zoomFactor * hh;
y += (int) Math.Round(newH);
}
ap.ScrollColumn = origScrollCol;
ap.ScrollRow = origScrollRow;
excelApp.ScreenUpdating = true;
Form f = new Form();
f.StartPosition = FormStartPosition.Manual;
f.Location = new Point(x, y);
f.Show();