| Graphics Libraries (HGL package) | Contents | Index
Graphics.HGL |
Portability | non-portable (requires concurrency)
Stability | provisional
Maintainer | libraries@haskell.org
Description
A simple graphics library.
Synopsis
module Graphics.HGL.Units
module Graphics.HGL.Run
module Graphics.HGL.Window
module Graphics.HGL.Draw
module Graphics.HGL.Key
module Graphics.HGL.Utils
Documentation
The Haskell Graphics Library is designed to give the programmer access to most interesting parts of the Win32 Graphics Device Interface and X11 library without exposing the programmer to the pain and anguish usually associated with using these interfaces. To give you a taste of what the library looks like, here is the obligatory "Hello World" program:
     module Main where

     import Graphics.HGL

     main :: IO ()
     main = runGraphics $
    	withWindow_ "Hello World Window" (300, 200) $ \ w -> do
    	drawInWindow w $ text (100, 100) "Hello World"
    	drawInWindow w $ ellipse (100, 80) (200, 180)
    	getKey w
Here's what each function does: `runGraphics` (defined in Graphics.HGL.Run) runs a graphical action in an appropriate environment. All the other functions of the library should be used inside `runGraphics`. `withWindow_` runs an action using a new `Window`, specifying the window title and size (300 pixels wide and 200 high). The window is closed when the action finishes. `drawInWindow` draws a `Graphic` (an abstract representation of a picture) on a `Window`. `text` creates a `Graphic` consisting of a string at the specified position. `ellipse` creates a `Graphic` consisting of an ellipse fitting inside a rectangle defined by the two points. These and other functions for defining, combining and modifying pictures are in Graphics.HGL.Draw. `getKey` waits for the user to press (and release) a key. (This is necessary here to prevent the window from closing before you have a chance to read what's on the screen.) The library is broken up into several pieces.
module Graphics.HGL.Units
module Graphics.HGL.Run
module Graphics.HGL.Window
module Graphics.HGL.Draw
module Graphics.HGL.Key
module Graphics.HGL.Utils
The module Graphics.HGL.Utils defines a number of convenience functions in terms of more primitive functions defined by other modules. For example, `withWindow_` is defined using `openWindowEx` and `closeWindow` (from Graphics.HGL.Window). `getKey` is defined using `getWindowEvent`, which waits for a range of user interface events. Instead of drawing several `Graphic` objects sequentially as in the above example, you can combine them into a single `Graphic` object using `overGraphic`.
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