# GSDisplayServer

fedor@gnu.org
Generated at 2026-06-27 19:09:52 +0000

Abstract display server class.

2002 Free Software Foundation, Inc.
GSDisplayServer

This is an abstract class which provides a framework for a device independant window server. A window server handles the very basic control of the computer display and input. This includes basic window creation and handling, event handling, cursors, and providing miscellaneous information about the display.

Typically a backend library will provide a concrete subclass which implements the device specific methods described below.

In almost all cases, you should not call these methods directly in an application. You should use the equivalent methods available elsewhere in the library (e.g. NSWindow, NSScreen, etc).

GNUstepGUI/GSDisplayServer.h
Description forthcoming.
Description forthcoming.
Description forthcoming.
Description forthcoming.
addDragTypes:
types
toWindow:
win
Convienience method that calls -addDragTypes:toWindow: using the server that controls win.
dragTypesForWindow:
win
Convienience method that calls -dragTypesForWindow: using the server that controls win.
removeDragTypes:
types
fromWindow:
win
Convienience method that calls -removeDragTypes:fromWindow: using the server that controls win.
serverWithAttributes:
attributes

Create a window server with attributes, which contains key/value pairs which describe the specifics of how the window server is to be initialized. Typically these values are specific to the concrete implementation. The current set of attributes that can be used with GSDisplayServer is.

GSDisplayName
GSDisplayNumber
GSScreenNumber

GSDisplayName is window server specific and shouldn't be used when creating a GSDisplayServer (although you can retrieve the value with the -attributes method). On X-Windows the value might be set to something like "host:d.s" where host is the host name, d is the display number and s is the screen number. GSDisplayNumber indicates the number of the display to open. GSScreenNumber indicates the number of the screen to display on. If not explicitly set, these attributes may be taked from environment variables or from other operating specific information.

In almost all applications one would only create a single instance of a window server. Although it is possible, it is unlikely that you would need more than one window server (and you would have to be very careful how you handled window creation and events in this case).

setCurrentServer:
server
Sets the current server that will be handling windows, events, etc. This method must be called after a window server is created in order to make it available to the rest of the GUI library
setDefaultServerClass:
aClass
Set the concrete subclass that will provide the device dependant implementation.
addDragTypes:
types
toWindow:
win
Add (increment count by 1) each drag type to those registered for the window. If this results in a change to the types registered in the counted set, return `YES`, otherwise return `NO`. Subclasses should override this method, call 'super' and take appropriate action if the method returns 'YES'.
attributes
Return information used to create the server
availableDepthsForScreen:
screen
Returns a null terminated list of possible window depths for screen.
beep
Play the System Beep
boundsForScreen:
screen
Returns the bounds, in pixels, for the indicated screen of the display.
closeServer
Causes the server to disconnect from the display. If the receiver is the current server, it removes itself and sets the current server to `nil`. Sending any more messages to the receiver after this is likely to cause severe problems and probably crash the application.
contentsOfScreen:
screen
inRect:
rect
Returns a screenshot of the specified rectangle of the specified screen. The mouse cursor should be ommitted from the returned image.
dragInfo
Returns an instance of a class which implements the NSDraggingInfo protocol.
dragTypesForWindow:
win
Returns the drag types set for the window win.
findWindowAt:
screenLocation
windowRef:
windowRef
excluding:
win
Description forthcoming.
glContextClass
Description forthcoming.
glPixelFormatClass
Description forthcoming.
handlesWindowDecorations
Returns `YES` if the backend handles window decorations and `NO` if the gui library must do that instead.
iconSize
Returns the size of icons and miniwindows for screen.
iconTileImage
Returns a display dependent NSImage which will be used as the background image for AppIcons and MiniWindows. Under Windowmaker, for example this could be a user specified gradient.
initWithAttributes:
attributes
Initializes the server. This typically causes the receiver to connect to the display (e.g. XOpenDisplay () on an X-Windows server).
removeDragTypes:
types
fromWindow:
win
Remove (decrement count by 1) each drag type from those registered for the window. If this results in a change to the types registered in the counted set, return `YES`, otherwise return `NO`. If given 'nil' as the array of types, remove ALL. Subclasses should override this method, call 'super' and take appropriate action if the method returns 'YES'.
resolutionForScreen:
screen
Returns the resolution, in points, for the indicated screen of the display.
restrictWindow:
win
toImage:
image
Description forthcoming.
screenList
Returns an array of NSNumbers, where each number describes a screen that is available on this display. The default screen is listed first.
serverDevice
Returns a display dependant pointer that describes the internal connection to the display. On X-Windows, for example, this is a pointer to the `Display` variable.
slideImage:
image
from:
from
to:
to
Description forthcoming.
windowDepthForScreen:
screen
Returns the default depth of windows that are created on screen.
windowDevice:
win
Returns a display dependant pointer that describes the internal window representation for win. On X-Windows, for example, this is a pointer to the `Window` variable.
Software documentation for the GSDisplayServer(EventOps) category
GNUstepGUI/GSDisplayServer.h
Description forthcoming.
_printEventQueue
Warning the underscore at the start of the name of this method indicates that it is private, for internal use only, and you should not use the method in your code.
discardEventsMatchingMask:
mask
beforeEvent:
limit
Steps through the event queue and removes all events whose timestamp is earlier than that of limit wand which match the supplied mask of event types.
getEventMatchingMask:
mask
beforeDate:
limit
inMode:
mode
dequeue:
flag
Scans through the event queue to find the first event whose type matches mask. If no event is found, then the current run loop is run in the specified mode to allow more events to arrive.
If a matching event is found, it is returned and either removed from or left in the queue according to flag.
If no matching event is found and the limit date is reached, this method returns `nil`.
postEvent:
anEvent
atStart:
flag
Posts an event to the event queue. The value of flag determines whether the event is inserted at the start of the queue or appended at the end.
Software documentation for the GSDisplayServer(WindowOps) category
GNUstepGUI/GSDisplayServer.h
Description forthcoming.
_setWindowOwnedByServer:
win
Warning the underscore at the start of the name of this method indicates that it is private, for internal use only, and you should not use the method in your code.
Tells the receiver that it owns the window described by win. Concrete subclasses must call this function when creating a window. Do not call this method in any other case, particularly for a window that has already been created
appOwnsMiniwindow
Returns `YES` if the application should create the miniwindow counterpart to the full size window and own it. Some display systems handle the miniwindow themselves. In this case the backend subclass should override this method to return `NO`.
capturemouse:
win
Grabs the pointer device so that all future mouse events will be directed only to the window win. If successful, the return value is `YES` and this message must be balanced by a -releasemouse message.
docedited:
edited
:
win
Sets the document edited flag for the window
flushwindowrect:
rect
:
win
Causes buffered graphics to be flushed to the screen. The value of rect is expressed in OpenStep window coordinates.
freecursor:
cid
Free the cursor given by the cid representation.
hideApplication:
win
Ask the window manager to hide all the application windows for us. Return whether they have been hidden.
hidecursor
Hides the cursor
imagecursor:
hotp
:
image
:
cid
Create a cursor from an image. Returns a pointer to the internal device representation that can be used later to make this cursor the current one
miniwindow:
win
Miniaturizes the window
mouseLocationOnScreen:
aScreen
window:
win
Returns the current mouse location on aScreen. If the pointer is not on aScreen, this method acts like -mouselocation . If aScreen is -1, then the location of the mouse on any screen is returned. The win pointer returns the window number of the GNUstep window that the mouse is in or 0 if it is not in a window.
The location is expressed as an offset from the bottom left corner of the screen.
mouselocation
Returns the current mouse location on the default screen. If the pointer is not on the default screen, an invalid point (-1,-1} is returned.
The location is expressed as an offset from the bottom left corner of the screen.
movewindow:
loc
:
win
Moves the bottom left corner of the window (including any border) to loc.
The position is expressed as an offset from the bottom left corner of the screen.
nativeWindow:
winref
:
frame
:
type
:
style
:
screen
Create all the backend structures for a reference to a native window and return the extend, backing type, style and screen for that window.
orderwindow:
op
:
otherWin
:
win

Causes the window to be ordered onto or off the screen depending on the value of op. The window is ordered relative to otherWin .

The effect of the various combinations of op and otherWin are:

op is NSWindowOut
The window is removed from the display and otherWinm is ignored.
op is NSWindowAbove and otherWin is zero
The window is placed above all other windows at the same level unless doing the current key window is at this level (in which case the window will be placed immediately below that).
op is NSWindowAbove and otherWin is minus one
The window is placed above all other windows at the same level even if doing that would place it above the current key window.
This is a special feature that [NSWindow -orderWindow:relativeTo:] uses to place the window correctly.
op is NSWindowBelow and otherWin is zero
The window is placed above all other windows at the same level.
op is NSWindowAbove and otherWin is a window on the display
The level of the window is set to be the same as that of otherWin and the window is placed immediately above otherWin.
op is NSWindowBelow and otherWin is a window on the display
The level of the window is set to be the same as that of otherWin and the window is placed immediately below otherWin.
placewindow:
frame
:
win
Moves and resizes the window on the screen as described by frame. The value of frame is a rectangle containing the entire window, including any border/decorations. Its position is expressed as an offset from the bottom left corner of the screen.
recolorcursor:
fg
:
bg
:
cid
Recolour the cursor given by the cid representation into having a foreground color fg and a background color bg.
releasemouse
Release a previous captured mouse from -capturemouse:
setIgnoreMouse:
ignoreMouse
:
win
Description forthcoming.
setMouseLocation:
mouseLocation
onScreen:
aScreen
Set mouse cursor position.
setParentWindow:
parentWin
forChildWindow:
childWin
Description forthcoming.
setShadow:
hasShadow
:
win
Sets the window shadow
setWindowdevice:
win
forContext:
ctxt
Sets the window device information for the NSGraphicsContext, typically by calling [NSGraphicsContext -GSSetDevice:::], although depending on the concrete implmentation, more information than this may need to be exchanged.
setalpha:
alpha
:
win
Sets the transparancy value for the whole window
setcursor:
cid
Set the cursor given by the cid representation as being the current cursor.
setcursorcolor:
fg
:
bg
:
cid
Set the cursor given by the cid representation as being the current cursor. The cursor has a foreground color fg and a background color bg. To keep the default color for the cursor, pass `nil` for fg and bg.
setinputfocus:
win
Forces focus to the window so that all key events are sent to this window
setinputstate:
state
:
win
Sets the input state for the window given by the GSWindowInputState constant. Instructs the window manager that the specified window is 'key', 'main', or just a normal window.
setmaxsize:
size
:
win
Set the maximum size (pixels) of the window
setminsize:
size
:
win
Set the minimum size (pixels) of the window
setresizeincrements:
size
:
win
Set the resize incremenet of the window
setwindowlevel:
level
:
win
Set the level of the window as in the [NSWindow -setLevel] method.
The use of window levels organises the window hierarchy into groups of windows at each level. It effects the operation of the -orderwindow::: method in the case where the position is 'above' or 'below' and the other window number is zero.
showcursor
Show a previously hidden cursor
standardcursor:
style
:
cid
Create a standard cursor (such as an arror or IBeam). Returns a pointer to the internal device representation that can be used later to make this cursor the current one
styleoffsets:
l
:
r
:
t
:
b
:
style
Returns the dimensions of window decorations added outside the drawable window frame by a window manager or equivalent. For instance, t gives the height of the title bar for the window.
If -handlesWindowDecorations returns `NO`, there are no decorations outside the drawable window frame and this method shouldn't be called.
stylewindow:
style
:
win
Sets the style of the window. See [NSWindow -styleMask] for a description of the available styles
termwindow:
win
Destroys the representation of the window and frees and memory associated with it.
titlewindow:
window_title
:
win
Sets the window title
window:
frame
:
type
:
style
Creates a window whose location and size is described by frame and whose backing store is described by type. This window is not mapped to the screen by this call.
Note that frame is the frame of the entire GNUstep window including borders, titlebar and other standard decorations.
If -handlesWindowDecorations returns `YES`, the backend will produce (and return the identifier of) a smaller drawable window inside this decorated area.
Use -styleoffsets::::: to determine the extent of the decorations and determine the size of the drawable area inside them.
window:
frame
:
type
:
style
:
screen
Like -window::: only there is an additional argument to specify which screen the window will display on
windowbacking:
type
:
win
Changes window's the backing store to type
windowbounds:
win
Returns the frame of the window on the screen.
The value of frame is a rectangle containing the entire window, including any border/decorations. Its position is expressed as an offset from the bottom left corner of the screen.
windowdepth:
win
Returns the depth of the window
windowdevice:
winNum
Sets the window device information for the current NSGraphicsContext, typically by calling [NSGraphicsContext -GSSetDevice:::], although depending on the concrete implmentation, more information than this may need to be exchanged.
windowlevel:
win
Returns the window level as in [NSWindow -level]
windowlist
Backends can override this method to return an array of window numbers ordered front to back. The front most window being the first object in the array. The default implementation returns the visible windows in an unspecified order.