When double-clicking TAStudio frame# cell, open dialog beside cell

src/BizHawk.Client.EmuHawk/CustomControls/InputRoll/InputRoll.cs

@@ -1882,6 +1882,14 @@ private Cell CalculatePointedCell(int x, int y)
 			? _columns.VisibleColumns.Last().Right
 			: 0;
 
+		/// <returns>in both orientations, the bottom-left corner of <paramref name="c"/>, relative to this control</returns>
+		public Point CellToPixels(Cell c)
+		{
+			var x = c.Column!.Right;
+			var y = RowsToPixels(c.RowIndex!.Value - FirstVisibleRow + 3); // magic 3? I expected 1
+			return _horizontalOrientation ? new(y, x) : new(x, y);
+		}
+
 		/// <summary>
 		/// Returns the RollColumn object at the specified visible pixel coordinate.
 		/// </summary>

src/BizHawk.Client.EmuHawk/tools/TAStudio/MarkerControl.cs

@@ -205,7 +205,8 @@ public void UpdateTextColumnWidth()
 			}
 		}
 
-		public void EditMarkerPopUp(TasMovieMarker marker)
+		/// <param name="location">bottom-left corner, in screen-space, or <see langword="null"/> to center on this control</param>
+		public void EditMarkerPopUp(TasMovieMarker marker, Point? location = null)
 		{
 			var markerFrame = marker.Frame;
 			var i = new InputPrompt
@@ -218,7 +219,15 @@ public void EditMarkerPopUp(TasMovieMarker marker)
 					? Markers.PreviousOrCurrent(markerFrame).Message
 					: ""
 			};
-
+			if (location is null)
+			{
+				i.CenterOn(this);
+			}
+			else
+			{
+				i.StartPosition = FormStartPosition.Manual;
+				i.Location = location.Value - new Size(0, i.Height);
+			}
 			if (!this.ShowDialogWithTempMute(i).IsOk()) return;
 
 			marker.Message = i.PromptText;

src/BizHawk.Client.EmuHawk/tools/TAStudio/TAStudio.ListView.cs

@@ -903,7 +903,9 @@ private void TasView_MouseDoubleClick(object sender, MouseEventArgs e)
 
 					if (existingMarker != null)
 					{
-						MarkerControl.EditMarkerPopUp(existingMarker);
+						var dialogLocation = this.ChildPointToScreen(TasView);
+						dialogLocation.Offset(TasView.CellToPixels(TasView.CurrentCell));
+						MarkerControl.EditMarkerPopUp(existingMarker, dialogLocation);
 					}
 					else
 					{