Graphics.UI.GLUT.Window

GLUT supports two types of windows: top-level windows and subwindows. Both types support OpenGL rendering and GLUT callbacks. There is a single identifier space for both types of windows.

Window identifiers

data Window

An opaque identifier for a top-level window or a subwindow.

Instances

Eq Window

Ord Window

Show Window

Creating and destroying (sub-)windows

Each created window has a unique associated OpenGL context. State changes to a window's associated OpenGL context can be done immediately after the window is created.

The display state of a window is initially for the window to be shown. But the window's display state is not actually acted upon until Graphics.UI.GLUT.Begin.mainLoop is entered. This means until Graphics.UI.GLUT.Begin.mainLoop is called, rendering to a created window is ineffective because the window can not yet be displayed.

The value returned by createWindow and createSubWindow is a unique identifier for the window, which can be used with currentWindow.

createWindow

Arguments

:: String

The window name

-> IO Window

The identifier for the newly created window

Create a top-level window. The given name will be provided to the window system as the window's name. The intent is that the window system will label the window with the name.Implicitly, the current window is set to the newly created window.

X Implementation Notes: The proper X Inter-Client Communication Conventions Manual (ICCCM) top-level properties are established. The WM_COMMAND property that lists the command line used to invoke the GLUT program is only established for the first window created.

createSubWindow

Arguments

:: Window

Identifier of the subwindow's parent window.

-> Position

Window position in pixels relative to parent window's origin.

-> Size

Window size in pixels

-> IO Window

The identifier for the newly created subwindow

Create a subwindow of the identified window with the given relative position and size. Implicitly, the current window is set to the newly created subwindow. Subwindows can be nested arbitrarily deep.

destroyWindow :: Window -> IO ()

Destroy the specified window and the window's associated OpenGL context, logical colormap (if the window is color index), and overlay and related state (if an overlay has been established). Any subwindows of the destroyed window are also destroyed by destroyWindow. If the specified window was the current window, the current window becomes invalid (currentWindow will contain Nothing).

parentWindow :: GettableStateVar (Maybe Window)

Contains the current window\'s parent. If the current window is a top-level window, Nothing is returned.

numSubWindows :: GettableStateVar Int

Contains the number of subwindows the current window has, not counting children of children.

Manipulating the current window

currentWindow :: StateVar (Maybe Window)

Controls the current window. It does not affect the layer in use for the window; this is done using Graphics.UI.GLUT.Overlay.layerInUse. Contains Nothing if no windows exist or the previously current window was destroyed. Setting the current window to Nothing is a no-op.

Re-displaying and double buffer management

postRedisplay :: Maybe Window -> IO ()

Mark the normal plane of given window (or the current window, if none is supplied) as needing to be redisplayed. The next iteration through Graphics.UI.GLUT.Begin.mainLoop, the window's display callback will be called to redisplay the window's normal plane. Multiple calls to postRedisplay before the next display callback opportunity generates only a single redisplay callback. postRedisplay may be called within a window's display or overlay display callback to re-mark that window for redisplay.

Logically, normal plane damage notification for a window is treated as a postRedisplay on the damaged window. Unlike damage reported by the window system, postRedisplay will not set to true the normal plane's damaged status (see Graphics.UI.GLUT.State.damaged).

Also, see Graphics.UI.GLUT.Overlay.postOverlayRedisplay.

swapBuffers :: IO ()

Mark the normal plane of the given window as needing to be redisplayed, otherwise the same as postRedisplay.

The advantage of this routine is that it saves the cost of using currentWindow (entailing an expensive OpenGL context switch), which is particularly useful when multiple windows need redisplays posted at the same time.

Perform a buffer swap on the layer in use for the current window. Specifically, swapBuffers promotes the contents of the back buffer of the layer in use of the current window to become the contents of the front buffer. The contents of the back buffer then become undefined. The update typically takes place during the vertical retrace of the monitor, rather than immediately after swapBuffers is called.

An implicit Graphics.Rendering.OpenGL.GL.FlushFinish.flush is done by swapBuffers before it returns. Subsequent OpenGL commands can be issued immediately after calling swapBuffers, but are not executed until the buffer exchange is completed.

If the layer in use is not double buffered, swapBuffers has no effect.

Changing the window geometry

Note that the requests by windowPosition, windowSize, and fullScreen are not processed immediately. A request is executed after returning to the main event loop. This allows multiple requests to the same window to be coalesced.

windowPosition and windowSize requests on a window will disable the full screen status of the window.

windowPosition :: StateVar Position

Controls the position of the current window. For top-level windows, parameters of Position are pixel offsets from the screen origin. For subwindows, the parameters are pixel offsets from the window's parent window origin.

In the case of top-level windows, setting windowPosition is considered only a request for positioning the window. The window system is free to apply its own policies to top-level window placement. The intent is that top-level windows should be repositioned according to the value of windowPosition.

windowSize :: StateVar Size

Controls the size of the current window. The parameters of Size are size extents in pixels. The width and height must be positive values.

In the case of top-level windows, setting windowSize is considered only a request for sizing the window. The window system is free to apply its own policies to top-level window sizing. The intent is that top-level windows should be reshaped according to the value of windowSize. Whether a reshape actually takes effect and, if so, the reshaped dimensions are reported to the program by a reshape callback.

fullScreen :: IO ()

Request that the current window be made full screen. The exact semantics of what full screen means may vary by window system. The intent is to make the window as large as possible and disable any window decorations or borders added the window system. The window width and height are not guaranteed to be the same as the screen width and height, but that is the intent of making a window full screen.

fullScreen is defined to work only on top-level windows.

X Implementation Notes: In the X implementation of GLUT, full screen is implemented by sizing and positioning the window to cover the entire screen and posting the _MOTIF_WM_HINTS property on the window requesting absolutely no decorations. Non-Motif window managers may not respond to _MOTIF_WM_HINTS.

fullScreenToggle :: IO ()

(freeglut only) Toggle between windowed and full screen mode.

Manipulating the stacking order

pushWindow and popWindow work on both top-level windows and subwindows. The effect of pushing and popping windows does not take place immediately. Instead the push or pop is saved for execution upon return to the GLUT event loop. Subsequent pop or push requests on a window replace the previously saved request for that window. The effect of pushing and popping top-level windows is subject to the window system's policy for restacking windows.

pushWindow :: IO ()

Change the stacking order of the current window relative to its siblings (lowering it).

popWindow :: IO ()

Change the stacking order of the current window relative to its siblings, bringing the current window closer to the top.

Managing a window's display status

data WindowStatus

The display status of a window.

Constructors

Shown

Hidden

Iconified

Instances

Eq WindowStatus

Ord WindowStatus

Show WindowStatus

windowStatus :: SettableStateVar WindowStatus

Controls the display status of the current window.

Note that the effect of showing, hiding, and iconifying windows does not take place immediately. Instead the requests are saved for execution upon return to the GLUT event loop. Subsequent show, hide, or iconification requests on a window replace the previously saved request for that window. The effect of hiding, showing, or iconifying top-level windows is subject to the window system's policy for displaying windows. Subwindows can't be iconified.

Changing the window/icon title

windowTitle and iconTitle should be set only when the /current window/ is a top-level window. Upon creation of a top-level window, the window and icon names are determined by the name given to createWindow. Once created, setting windowTitle and iconTitle can change the window and icon names respectively of top-level windows. Each call requests the window system change the title appropriately. Requests are not buffered or coalesced. The policy by which the window and icon name are displayed is window system dependent.

windowTitle :: SettableStateVar String

Controls the window title of the current top-level window.

iconTitle :: SettableStateVar String

Controls the icon title of the current top-level window.

Cursor management

data Cursor

The different cursor images GLUT supports.

Constructors

RightArrow

Arrow pointing up and to the right.

LeftArrow

Arrow pointing up and to the left.

Info

Pointing hand.

Destroy

Skull & cross bones.

Help

Question mark.

Cycle

Arrows rotating in a circle.

Spray

Spray can.

Wait

Wrist watch.

Text

Insertion point cursor for text.

Crosshair

Simple cross-hair.

UpDown

Bi-directional pointing up & down.

LeftRight

Bi-directional pointing left & right.

TopSide

Arrow pointing to top side.

BottomSide

Arrow pointing to bottom side.

LeftSide

Arrow pointing to left side.

RightSide

Arrow pointing to right side.

TopLeftCorner

Arrow pointing to top-left corner.

TopRightCorner

Arrow pointing to top-right corner.

BottomRightCorner

Arrow pointing to bottom-left corner.

BottomLeftCorner

Arrow pointing to bottom-right corner.

Inherit

Use parent's cursor.

None

Invisible cursor.

FullCrosshair

Full-screen cross-hair cursor (if possible, otherwise Crosshair).

Instances

Eq Cursor

Ord Cursor

Show Cursor

cursor :: StateVar Cursor

Change the cursor image of the current window. Each call requests the window system change the cursor appropriately. The cursor image when a window is created is Inherit. The exact cursor images used are implementation dependent. The intent is for the image to convey the meaning of the cursor name. For a top-level window, Inherit uses the default window system cursor.

X Implementation Notes: GLUT for X uses SGI's _SGI_CROSSHAIR_CURSOR convention to access a full-screen cross-hair cursor if possible.

pointerPosition :: SettableStateVar Position

Setting pointerPosition warps the window system's pointer to a new location relative to the origin of the current window by the specified pixel offset, which may be negative. The warp is done immediately.

If the pointer would be warped outside the screen's frame buffer region, the location will be clamped to the nearest screen edge. The window system is allowed to further constrain the pointer's location in window system dependent ways.

Good advice from Xlib's XWarpPointer man page: "There is seldom any reason for calling this function. The pointer should normally be left to the user."