Problem Statement

The task is to determine the maximum height and width of a window that can fit within the physical display area of the screen without scrolling. This is effectively the screen size (not the total desktop area, which could be bigger than the screen display area) in pixels minus any adjustments for window decorations and menubars. The idea is to determine the physical display parameters for the maximum height and width of the usable display area in pixels (without scrolling). The values calculated should represent the usable desktop area of a window maximized to fit the the screen.

For multiple monitors, the values calculated should represent the size of the usable display area on the monitor which is related to the task (i.e.:   the monitor which would display a window if such instructions were given). For a tiling window manager, the values calculated should represent the maximum height and width of the display area of the maximum size a window can be created (without scrolling). This would typically be a full screen window (minus any areas occupied by desktop bars), unless the window manager has restrictions that prevents the creation of a full screen window, in which case the values represent the usable area of the desktop that occupies the maximum permissible window size (without scrolling).

Let's start with the solution:

SysGet, MonitorCount, MonitorCount
SysGet, MonitorPrimary, MonitorPrimary
MsgBox, Monitor Count:`t%MonitorCount%`nPrimary Monitor:`t%MonitorPrimary%
Loop, %MonitorCount%
{
    SysGet, MonitorName, MonitorName, %A_Index%
    SysGet, Monitor, Monitor, %A_Index%
    SysGet, MonitorWorkArea, MonitorWorkArea, %A_Index%
    MsgBox, % "Monitor:`t#" A_Index 
            . "`nName:`t" MonitorName
            . "`nLeft:`t" MonitorLeft "(" MonitorWorkAreaLeft " work)"
            . "`nTop:`t" MonitorTop " (" MonitorWorkAreaTop " work)"
            . "`nRight:`t" MonitorRight " (" MonitorWorkAreaRight " work)"
            . "`nBottom:`t" MonitorBottom " (" MonitorWorkAreaBottom " work)"
}