Returns, as multiple values, a screen rectangle covering the full area of all the monitors associated with a screen.
capi
virtual-screen-geometry screen => x, y, width, height
|   screen⇩  |    
A CAPI screen.  | 
|   x⇩  |    
An integer.  | 
|   y⇩  |    
An integer.  | 
|   width⇩  |    
A positive integer.  | 
|   height⇩  |    
A positive integer.  | 
The function virtual-screen-geometry returns the "virtual" geometry of the screen screen, which is a screen rectangle covering the full area of all the monitors that are associated with screen.
The screen rectangle is at coordinates x and y as offsets from the top-left of the primary screen, with dimensions width and height.
pane-screen-internal-geometry
screen-internal-geometries
screen-monitor-geometries
4.3 Support for multiple monitors
11.6 Querying and modifying interface geometry
CAPI User Guide and Reference Manual (Macintosh version) - 01 Dec 2021 19:31:27