An Object a is a pointer to an object of type a. The a parameter is used to encode the inheritance relation. When the type parameter is unit (), it denotes an object of exactly that class, when the parameter is a type variable a, it specifies an object that is at least an instance of that class. For example in wxWidgets, we have the following class hierarchy:

EvtHandler
  |- Window
       |- Frame
       |- Control
           |- Button
           |- Radiobox

In wxHaskell, all the creation functions will return objects of exactly that class and use the () type:

frameCreate :: Window a -> ... -> IO (Frame ())
buttonCreate :: Window a -> ... -> IO (Button ())
...

In contrast, all the this (or self) pointers of methods can take objects of any instance of that class and have a type variable, for example:

windowSetClientSize :: Window a -> Size -> IO ()
controlSetLabel     :: Control a -> String -> IO ()
buttonSetDefault    :: Button a -> IO ()

This means that we can use windowSetClientSize on any window, including buttons and frames, but we can only use controlSetLabel on controls, not including frames.

In wxHaskell, this works since a Frame () is actually a type synonym for Window (CFrame ()) (where CFrame is an abstract data type). We can thus pass a value of type Frame () to anything that expects some Window a. For a button this works too, as it is a synonym for Control (CButton ()) which is in turn a synonym for Window (CControl (CButton ())). Note that we can't pass a frame to something that expects a value of type Control a. Of course, a Window a is actually a type synonym for EvtHandler (CWindow a). If you study the documentation in Graphics.UI.WX.Classes closely, you can discover where this chain ends :-).

Objects are not automatically deleted. Normally you can use a delete function like windowDelete to delete an object. However, almost all objects in the wxWidgets library are automatically deleted by the library. The only objects that should be used with care are resources as bitmaps, fonts and brushes.

A null object. Use with care.

Test for null object.

Cast an object to another type. Use with care.

Is this a managed object?

Delete a wxObject, works for managed and unmanaged objects.

Create an unmanaged object.

Create a managed object that will be deleted using |wxObject_SafeDelete|.

Do something with the object pointer.

Extract the object pointer and raise an exception if NULL. Otherwise continue with the valid pointer.

Return an unmanaged object.

Create a managed object that will be deleted using |wxObject_SafeDelete|.

Finalize a managed object manually. (No effect on unmanaged objects.)

Remove the finalizer on a managed object. (No effect on unmanaged objects.)

An Id is used to identify objects during event handling.

A Style is normally used as a flag mask to specify some window style

An EventId is identifies specific events.

Convert a Haskell Bool to its numeric representation

Convert a Boolean in numeric representation to a Haskell value

A point has an x and y coordinate. Coordinates are normally relative to the upper-left corner of their view frame, where a positive x goes to the right and a positive y to the bottom of the view.

Construct a point.

Shorter function to construct a point.

Point at the origin.

A null point is not a legal point (x and y are -1) and can be used for some wxWidgets functions to select a default point.

A Size has a width and height.

Short function to construct a size

A null size is not a legal size (width and height are -1) and can be used for some wxWidgets functions to select a default size.

A vector with an x and y delta.

Construct a vector.

Short function to construct a vector.

A zero vector

A null vector has a delta x and y of -1 and can be used for some wxWidgets functions to select a default vector.

A rectangle is defined by the left x coordinate, the top y coordinate, the width and the height.

Create a rectangle at a certain (upper-left) point with a certain size.

Construct a (positive) rectangle between two (arbitrary) points.

Create a rectangle of a certain size with the upper-left corner at (pt 0 0).

An empty rectangle at (0,0).

An null rectangle is not a valid rectangle (Rect -1 -1 -1 -1) but can used for some wxWidgets functions to select a default rectangle. (i.e. frameCreate).

Get the size of a rectangle.

An abstract data type to define colors.

Note: Haddock 0.8 and 0.9 doesn't support GeneralizedNewtypeDeriving. So, This class doesn't have IArray class's unboxed array instance now. If you want to use this type with unboxed array, you must write code like this.

{-# LANGUAGE GeneralizedNewtypeDeriving, StandaloneDeriving, MultiParamTypeClasses #-}
import Graphics.UI.WXCore.WxcTypes
...
deriving instance IArray UArray Color

We can't derive MArray class's unboxed array instance this way. This is a bad point of current MArray class definition.

Create a color from a red/green/blue triple.

Create a color from a red/green/blue triple.

Create a color from a red/green/blue/alpha quadruple.

Create a color from a red/green/blue/alpha quadruple.

Returns a red color component

Returns a green color component

Returns a blue color component

Returns a alpha channel component

Return an Int where the three least significant bytes contain the red, green, and blue component of a color.

Set the color according to an rgb integer. (see rgbIntFromColor).

Return an Num class's numeric representation where the three least significant the red, green, and blue component of a color.

Set the color according to Integral class's numeric representation. (see rgbaIntFromColor).

deprecated: use colorIsOk instead.

Check of a color is valid (Colour::IsOk)

Temporarily store a list of storable values in memory (like with, but for multiple elements).

Identifies tree items. Note: Replaces the TreeItemId object and takes automatically care of allocation issues.

Invalid tree item.

Is a tree item ok? (i.e. not invalid).

A C string is a reference to an array of C characters terminated by NUL.

Marshal a Haskell string into a NUL terminated C string using temporary storage.

• the Haskell string may not contain any NUL characters
• the memory is freed when the subcomputation terminates (either normally or via an exception), so the pointer to the temporary storage must not be used after this.

A C wide string is a reference to an array of C wide characters terminated by NUL.

Marshal a Haskell string into a NUL terminated C wide string using temporary storage.

• the Haskell string may not contain any NUL characters
• the memory is freed when the subcomputation terminates (either normally or via an exception), so the pointer to the temporary storage must not be used after this.

Haskell type representing the C int type.

A signed integral type that can be losslessly converted to and from Ptr. This type is also compatible with the C99 type intptr_t, and can be marshalled to and from that type safely.

A Word is an unsigned integral type, with the same size as Int.

8-bit unsigned integer type

64-bit signed integer type

Haskell type representing the C double type.

Haskell type representing the C char type.

Haskell type representing the C wchar_t type.

A value of type Ptr a represents a pointer to an object, or an array of objects, which may be marshalled to or from Haskell values of type a.

The type a will often be an instance of class Storable which provides the marshalling operations. However this is not essential, and you can provide your own operations to access the pointer. For example you might write small foreign functions to get or set the fields of a C struct.

Null pointer, use with care.

Test for null.

Cast a pointer type, use with care.

The type ForeignPtr represents references to objects that are maintained in a foreign language, i.e., that are not part of the data structures usually managed by the Haskell storage manager. The essential difference between ForeignPtrs and vanilla memory references of type Ptr a is that the former may be associated with finalizers. A finalizer is a routine that is invoked when the Haskell storage manager detects that - within the Haskell heap and stack - there are no more references left that are pointing to the ForeignPtr. Typically, the finalizer will, then, invoke routines in the foreign language that free the resources bound by the foreign object.

The ForeignPtr is parameterised in the same way as Ptr. The type argument of ForeignPtr should normally be an instance of class Storable.

A value of type FunPtr a is a pointer to a function callable from foreign code. The type a will normally be a foreign type, a function type with zero or more arguments where

• the argument types are marshallable foreign types, i.e. Char, Int, Double, Float, Bool, Int8, Int16, Int32, Int64, Word8, Word16, Word32, Word64, Ptr a, FunPtr a, StablePtr a or a renaming of any of these using newtype.
• the return type is either a marshallable foreign type or has the form IO t where t is a marshallable foreign type or ().

A value of type FunPtr a may be a pointer to a foreign function, either returned by another foreign function or imported with a a static address import like

foreign import ccall "stdlib.h &free"
  p_free :: FunPtr (Ptr a -> IO ())

or a pointer to a Haskell function created using a wrapper stub declared to produce a FunPtr of the correct type. For example:

type Compare = Int -> Int -> Bool
foreign import ccall "wrapper"
  mkCompare :: Compare -> IO (FunPtr Compare)

Calls to wrapper stubs like mkCompare allocate storage, which should be released with freeHaskellFunPtr when no longer required.

To convert FunPtr values to corresponding Haskell functions, one can define a dynamic stub for the specific foreign type, e.g.

type IntFunction = CInt -> IO ()
foreign import ccall "dynamic"
  mkFun :: FunPtr IntFunction -> IntFunction