| gtk-0.11.2: Binding to the Gtk+ graphical user interface library. | Contents | Index
Graphics.UI.Gtk.General.General |
Portability | portable (depends on GHC)
Stability | provisional
Maintainer | gtk2hs-users@lists.sourceforge.net
Contents
Initialisation Support for OS threads Main event loop Less commonly used event loop functions Grab widgets Timeout and idle callbacks
Description
library initialization, main event loop, and events
Synopsis
initGUI :: IO [String]
unsafeInitGUIForThreadedRTS :: IO [String]
postGUISync :: IO a -> IO a
postGUIAsync :: IO () -> IO ()
threadsEnter :: IO ()
threadsLeave :: IO ()
mainGUI :: IO ()
mainQuit :: IO ()
eventsPending :: IO Int
mainLevel :: IO Int
mainIteration :: IO Bool
mainIterationDo :: Bool -> IO Bool
mainDoEvent :: EventM t ()
grabAdd :: WidgetClass wd => wd -> IO ()
grabGetCurrent :: IO (Maybe Widget)
grabRemove :: WidgetClass w => w -> IO ()
type Priority = Int
priorityLow :: Int
priorityDefaultIdle :: Int
priorityHighIdle :: Int
priorityDefault :: Int
priorityHigh :: Int
timeoutAdd :: IO Bool -> Int -> IO HandlerId
timeoutAddFull :: IO Bool -> Priority -> Int -> IO HandlerId
timeoutRemove :: HandlerId -> IO ()
idleAdd :: IO Bool -> Priority -> IO HandlerId
idleRemove :: HandlerId -> IO ()
inputAdd :: FD -> [IOCondition] -> Priority -> IO Bool -> IO HandlerId
inputRemove :: HandlerId -> IO ()
data IOCondition
= IOIn
| IOOut
| IOPri
| IOErr
| IOHup
| IOInvalid
type HandlerId = CUInt
type FD = Int
Initialisation
initGUI :: IO [String]
Initialize the GUI. This must be called before any other function in the Gtk2Hs library. This function initializes the GUI toolkit and parses all Gtk specific arguments. The remaining arguments are returned. If the initialization of the toolkit fails for whatever reason, an exception is thrown. Throws: `error "Cannot initialize GUI."` If you want to use Gtk2Hs and in a multi-threaded application then it is your obligation to ensure that all calls to Gtk+ happen in a single OS thread. If you want to make calls to Gtk2Hs functions from a Haskell thread other than the one that calls this functions and `mainGUI` then you will have to 'post' your GUI actions to the main GUI thread. You can do this using `postGUISync` or `postGUIAsync`. See also `threadsEnter`.
Support for OS threads
unsafeInitGUIForThreadedRTS :: IO [String]
postGUISync :: IO a -> IO a
Post an action to be run in the main GUI thread. The current thread blocks until the action completes and the result is returned.
postGUIAsync :: IO () -> IO ()
Post an action to be run in the main GUI thread. The current thread continues and does not wait for the result of the action.
threadsEnter :: IO ()
Acquire the global Gtk lock. During normal operation, this lock is held by the thread from which all interaction with Gtk is performed. When calling `mainGUI`, the thread will release this global lock before it waits for user interaction. During this time it is, in principle, possible to use a different OS thread (any other Haskell thread that is bound to the Gtk OS thread will be blocked anyway) to interact with Gtk by explicitly acquiring the lock, calling Gtk functions and releasing the lock. However, the Gtk functions that are called from this different thread may not trigger any calls to the OS since this will lead to a crash on Windows (the Win32 API can only be used from a single thread). Since it is very hard to tell which function only interacts on Gtk data structures and which function call actual OS functions, it is best not to use this feature at all. A better way to perform updates in the background is to spawn a Haskell thread and to perform the update to Gtk widgets using `postGUIAsync` or `postGUISync`. These will execute their arguments from the main loop, that is, from the OS thread of Gtk, thereby ensuring that any Gtk and OS function can be called.
threadsLeave :: IO ()
Release the global Gtk lock. The use of this function is not recommended. See `threadsEnter`.
Main event loop
mainGUI :: IO ()
Run the Gtk+ main event loop.
mainQuit :: IO ()
Exit the main event loop.
Less commonly used event loop functions
eventsPending :: IO Int
Inquire the number of events pending on the event queue
mainLevel :: IO Int
Inquire the main loop level. Callbacks that take more time to process can call `mainIteration` to keep the GUI responsive. Each time the main loop is restarted this way, the main loop counter is increased. This function returns this counter.
mainIteration :: IO Bool
Process an event, block if necessary. Returns `True` if `mainQuit` was called while processing the event.
mainIterationDo :: Bool -> IO Bool
Process a single event. Called with `True`, this function behaves as `mainIteration` in that it waits until an event is available for processing. It will return immediately, if passed `False`. Returns `True` if the `mainQuit` was called while processing the event.
mainDoEvent :: EventM t ()
Processes a single GDK event. This is public only to allow filtering of events between GDK and GTK+. You will not usually need to call this function directly. While you should not call this function directly, you might want to know how exactly events are handled. So here is what this function does with the event: 1. Compress enterleave notify events. If the event passed build an enterleave pair together with the next event (peeked from GDK) both events are thrown away. This is to avoid a backlog of (de-)highlighting widgets crossed by the pointer. 2. Find the widget which got the event. If the widget can't be determined the event is thrown away unless it belongs to a INCR transaction. In that case it is passed to selectionIncrEvent. 3. Then the event is passed on a stack so you can query the currently handled event with getCurrentEvent. 4. The event is sent to a widget. If a grab is active all events for widgets that are not in the contained in the grab widget are sent to the latter with a few exceptions: Deletion and destruction events are still sent to the event widget for obvious reasons. Events which directly relate to the visual representation of the event widget. Leave events are delivered to the event widget if there was an enter event delivered to it before without the paired leave event. Drag events are not redirected because it is unclear what the semantics of that would be. Another point of interest might be that all key events are first passed through the key snooper functions if there are any. Read the description of keySnooperInstall if you need this feature. 5. After finishing the delivery the event is popped from the event stack.
Grab widgets
grabAdd :: WidgetClass wd => wd -> IO ()
add a grab widget
grabGetCurrent :: IO (Maybe Widget)
inquire current grab widget
grabRemove :: WidgetClass w => w -> IO ()
remove a grab widget
Timeout and idle callbacks
type Priority = Int
Priorities for installing callbacks.
priorityLow :: Int
priorityDefaultIdle :: Int
priorityHighIdle :: Int
priorityDefault :: Int
priorityHigh :: Int
timeoutAdd :: IO Bool -> Int -> IO HandlerId
Sets a function to be called at regular intervals, with the default priority `priorityDefault`. The function is called repeatedly until it returns `False`, after which point the timeout function will not be called again. The first call to the function will be at the end of the first interval. Note that timeout functions may be delayed, due to the processing of other event sources. Thus they should not be relied on for precise timing. After each call to the timeout function, the time of the next timeout is recalculated based on the current time and the given interval (it does not try to 'catch up' time lost in delays). This function differs from `timeoutAdd` in that the action will be executed within the global Gtk+ lock. It is therefore possible to call Gtk+ functions from the action.
timeoutAddFull :: IO Bool -> Priority -> Int -> IO HandlerId
Sets a function to be called at regular intervals, with the given priority. The function is called repeatedly until it returns `False`, after which point the timeout function will not be called again. The first call to the function will be at the end of the first interval. Note that timeout functions may be delayed, due to the processing of other event sources. Thus they should not be relied on for precise timing. After each call to the timeout function, the time of the next timeout is recalculated based on the current time and the given interval (it does not try to 'catch up' time lost in delays). This function differs from `timeoutAddFull` in that the action will be executed within the global Gtk+ lock. It is therefore possible to call Gtk+ functions from the action.
timeoutRemove :: HandlerId -> IO ()
Remove a previously added timeout handler by its `HandlerId`.
idleAdd :: IO Bool -> Priority -> IO HandlerId
Add a callback that is called whenever the system is idle. A priority can be specified via an integer. This should usually be `priorityDefaultIdle`. If the function returns `False` it will be removed. This function differs from `idleAdd` in that the action will be executed within the global Gtk+ lock. It is therefore possible to call Gtk+ functions from the action.
idleRemove :: HandlerId -> IO ()
Remove a previously added idle handler by its `HandlerId`.
inputAdd
:: FD | a file descriptor
-> [IOCondition] | the condition to watch for
-> Priority | the priority of the event source
-> IO Bool | the function to call when the condition is satisfied. The function should return False if the event source should be removed.
-> IO HandlerId | the event source id
Adds the file descriptor into the main event loop with the given priority. This function differs from `inputAdd` in that the action will be executed within the global Gtk+ lock. It is therefore possible to call Gtk+ functions from the action.
inputRemove :: HandlerId -> IO ()
data IOCondition
Flags representing a condition to watch for on a file descriptor. `IOIn` There is data to read. [`IOOut`] Data can be written (without blocking). [`IOPri`] There is urgent data to read. [`IOErr`] Error condition. [`IOHup`] Hung up (the connection has been broken, usually for pipes and sockets). [`IOInvalid`] Invalid request. The file descriptor is not open.
Constructors
IOIn |
IOOut |
IOPri |
IOErr |
IOHup |
IOInvalid |
Instances
Bounded IOCondition |
Enum IOCondition |
Eq IOCondition |
Flags IOCondition |
type HandlerId = CUInt
type FD = Int
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