isMySheetVisible(): Boolean;
The isMySheetVisible method of the Control class provides a control with the ability to determine if the sheet of a Folder control on which it is placed is the current visible sheet.
The control does not need to be a direct child of the folder.
Folders provide the ability to share the same screen space for a number of control images. The sheets of the folders are special group boxes on which controls are placed. The caption of each sheet is displayed in tabs that can be selected above the images. One sheet only is displayed at any time. If the control is not on a sheet, the isMySheetVisible method returns true.
Setting the focus to a control on a sheet that is not the current topSheet causes that sheet to become the top sheet.