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.



Considerations

--- Multiple Monitors

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).

--- Tiling Window Managers
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).




import Graphics.UI.Gtk
import Control.Monad (when)
import Control.Monad.Trans (liftIO)
 
maximumWindowDimensions :: IO ()
maximumWindowDimensions = do
    -- initialize the internal state of the GTK toolkit
    initGUI
    -- create a window
    window <- windowNew
    -- quit the application when the window is closed
    on window objectDestroy mainQuit
    -- query the size of the window when its dimensions change
    on window configureEvent printSize
    -- get the screen the window will be drawn upon
    screen <- windowGetScreen window
    -- get the size of the screen
    x <- screenGetWidth screen
    y <- screenGetHeight screen
    -- print the dimensions of the screen
    putStrLn ("The screen is " ++ show x ++ " pixels wide and " ++
        show y ++ " pixels tall for an undecorated fullscreen window.")
    -- maximize the window and show it. printSize will then be called
    windowMaximize window
    widgetShowAll window
    -- run the main GTK loop.
    -- close the window manually.
    mainGUI
 
-- On my Xfce4 desktop, the configure_event is called three times when a
-- top level window is maximized. The first time, the window size
-- returned is the size prior to maximizing, and the last two times
-- it is the size after maximizing.
-- If the window is (un)maximized manually, the size returned is always
-- the size of the unmaximized window.
-- That means: either GTK or Xfce4 does not handle window maximization
-- correctly, or the GTK bindings for Haskell are buggy, or there is an
-- error in this program.
 
printSize :: EventM EConfigure Bool
printSize = do
    -- get the window that has been resized
    w <- eventWindow
    -- is the window maximized?
    s <- liftIO $ drawWindowGetState w
    when (WindowStateMaximized `elem` s) $ do
        -- get the size of the window that has been resized
        (x, y) <- eventSize
        -- print the dimensions out
        liftIO $ putStrLn ("The inner window region is now " ++ show x ++
            " pixels wide and " ++ show y ++ " pixels tall.")
    return True