Graphics Libraries (HGL package)ContentsIndex
Graphics.SOE
Portabilitynon-portable (requires concurrency)
Stabilitystable
Maintainerlibraries@haskell.org
Contents
Getting started
Windows
General windows
Drawing
Color
Drawing text
Drawing shapes
Regions
User interaction
Keyboard events
Mouse events
General events
Time
Description

The graphics library used in The Haskell School of Expression, by Paul Hudak, cf http://www.haskell.org/soe/.

Notes:

  • This module is called SOEGraphics in the book. It is a cut down version of Graphics.HGL, with the interface frozen to match the book.
  • In chapters 13, 17 and 19 of the book, there are imports of modules Win32Misc and Word. These should be omitted, as timeGetTime and word32ToInt are provided by this module.
Synopsis
runGraphics :: IO () -> IO ()
type Title = String
type Size = (Int, Int)
data Window
openWindow :: Title -> Size -> IO Window
getWindowSize :: Window -> IO Size
clearWindow :: Window -> IO ()
drawInWindow :: Window -> Graphic -> IO ()
drawInWindowNow :: Window -> Graphic -> IO ()
setGraphic :: Window -> Graphic -> IO ()
closeWindow :: Window -> IO ()
openWindowEx :: Title -> Maybe Point -> Maybe Size -> RedrawMode -> Maybe Word32 -> IO Window
data RedrawMode
drawGraphic :: RedrawMode
drawBufferedGraphic :: RedrawMode
type Graphic = Draw ()
emptyGraphic :: Graphic
overGraphic :: Graphic -> Graphic -> Graphic
overGraphics :: [Graphic] -> Graphic
data Color
= Black
| Blue
| Green
| Cyan
| Red
| Magenta
| Yellow
| White
withColor :: Color -> Graphic -> Graphic
text :: Point -> String -> Graphic
type Point = (Int, Int)
ellipse :: Point -> Point -> Graphic
shearEllipse :: Point -> Point -> Point -> Graphic
line :: Point -> Point -> Graphic
polygon :: [Point] -> Graphic
polyline :: [Point] -> Graphic
polyBezier :: [Point] -> Graphic
type Angle = Double
arc :: Point -> Point -> Angle -> Angle -> Graphic
data Region
createRectangle :: Point -> Point -> Region
createEllipse :: Point -> Point -> Region
createPolygon :: [Point] -> Region
andRegion :: Region -> Region -> Region
orRegion :: Region -> Region -> Region
xorRegion :: Region -> Region -> Region
diffRegion :: Region -> Region -> Region
drawRegion :: Region -> Graphic
getKey :: Window -> IO Char
getLBP :: Window -> IO Point
getRBP :: Window -> IO Point
data Event
= Key {
char :: Char
isDown :: Bool
}
| Button {
pt :: Point
isLeft :: Bool
isDown :: Bool
}
| MouseMove {
pt :: Point
}
| Resize
| Closed
maybeGetWindowEvent :: Window -> IO (Maybe Event)
getWindowEvent :: Window -> IO Event
Word32
getWindowTick :: Window -> IO ()
timeGetTime :: IO Word32
word32ToInt :: Word32 -> Int
Getting started
runGraphics :: IO () -> IO ()
Initialize the system to do graphics, run an action while collecting user interface events and forwarding them to the action, and then clean up everything else at the end. The other functions of the library may only be used inside runGraphics.
Windows
type Title = String
Title of a window.
type Size = (Int, Int)
A (width, height) pair, both measured in pixels.
data Window
openWindow :: Title -> Size -> IO Window
Create a window with the given title and size.
getWindowSize :: Window -> IO Size
The current size of the window.
clearWindow :: Window -> IO ()
Erase all drawing in the window. (That is, set the Graphic held by the window to emptyGraphic.)
drawInWindow :: Window -> Graphic -> IO ()
Draw the given graphic on the window, on top of anything that is already there. (That is, combine the given Graphic and the one held by the window using overGraphic, store the result in the window, and display it.)
drawInWindowNow :: Window -> Graphic -> IO ()
Another name for drawInWindow, retained for backwards compatibility.
setGraphic :: Window -> Graphic -> IO ()
Set the current drawing in a window.
closeWindow :: Window -> IO ()
Close the window.
General windows
openWindowEx
:: Titlethe title of the window
-> Maybe Pointthe initial position of the window
-> Maybe Sizethe initial size of the window
-> RedrawModehow to display a graphic on the window
-> Maybe Word32optionally attach a timer to the window, with the specified time (in milliseconds) between ticks.
-> IO Window
an extended version of openWindow.
data RedrawMode
How to draw in a window.
drawGraphic :: RedrawMode
Draw directly to the window (slightly faster than drawBufferedGraphic, but more prone to flicker).
drawBufferedGraphic :: RedrawMode
Use a double buffer to reduce flicker and thus improve the look of animations.
Drawing
type Graphic = Draw ()
An abstract representation of an image.
emptyGraphic :: Graphic
An empty drawing.
overGraphic :: Graphic -> Graphic -> Graphic
A composite drawing made by overlaying the first argument on the second.
overGraphics :: [Graphic] -> Graphic
Overlay a list of drawings.
Color
data Color
Named colors.
Constructors
Black
Blue
Green
Cyan
Red
Magenta
Yellow
White
show/hide Instances
withColor :: Color -> Graphic -> Graphic
Set the default drawing color for a Graphic.
Drawing text
text :: Point -> String -> Graphic
Render a String positioned relative to the specified Point.
Drawing shapes
type Point = (Int, Int)
A position within a window, measured in pixels to the right and down from the top left corner.
ellipse
:: Pointa corner of the rectangle bounding the ellipse.
-> Pointthe opposite corner of the rectangle bounding the ellipse.
-> Graphica filled shape
A filled ellipse that fits inside a rectangle defined by two Points on the window.
shearEllipse
:: Pointa corner of the bounding parallelogram.
-> Pointanother corner of the parallelogram, adjacent to the first.
-> Pointanother corner of the parallelogram, adjacent to the first and thus opposite to the second.
-> Graphica filled shape
A filled sheared ellipse that fits inside a parallelogram defined by three Points on the window. This function is implemented using polygons on both Win32 and X11.
line :: Point -> Point -> Graphic
A line between two Points.
polygon :: [Point] -> Graphic
A filled polygon defined by a list of Points.
polyline :: [Point] -> Graphic
A series of lines through a list of Points.
polyBezier :: [Point] -> Graphic
A series of (unfilled) Bezier curves defined by a list of 3n+1 control Points. This function is not supported on X11 (it yields an error message and a polyline).
type Angle = Double
An angle in degrees (0 to 360).
arc
:: Pointa corner of the rectangle bounding the ellipse.
-> Pointthe opposite corner of the rectangle bounding the ellipse.
-> Anglethe start angle of the arc, measured counter-clockwise from the horizontal.
-> Anglethe extent of the arc, measured counter-clockwise from the start angle.
-> Graphica filled shape
A filled arc from an ellipse.
Regions
data Region
createRectangle :: Point -> Point -> Region
A rectangular region, with the given points as opposite corners.
createEllipse :: Point -> Point -> Region
An elliptical region that fits in the rectangle with the given points as opposite corners.
createPolygon :: [Point] -> Region
A polygonal region defined by a list of Points.
andRegion :: Region -> Region -> Region
The intersection of two regions.
orRegion :: Region -> Region -> Region
The union of two regions.
xorRegion :: Region -> Region -> Region
The symmetric difference of two regions.
diffRegion :: Region -> Region -> Region
The part of the first region that is not also in the second.
drawRegion :: Region -> Graphic
Draw a Region in the current color.
User interaction
Keyboard events
getKey :: Window -> IO Char
Wait until a key is pressed and released, and return the corresponding character.
Mouse events
getLBP :: Window -> IO Point
Wait for a press of the left mouse button, and return the position of the mouse cursor.
getRBP :: Window -> IO Point
Wait for a press of the right mouse button, and return the position of the mouse cursor.
General events
data Event
User interface events
Constructors
Keyoccurs when a key was pressed or released.
char :: Charcharacter corresponding to the key
isDown :: Boolif True, the key was pressed; otherwise it was released
Buttonoccurs when a mouse button is pressed or released.
pt :: Pointthe position of the mouse cursor
isLeft :: Boolif True, it was the left button
isDown :: Boolif True, the button was pressed; otherwise it was released
MouseMoveoccurs when the mouse is moved inside the window.
pt :: Pointthe position of the mouse cursor
Resizeoccurs when the window is resized. The new window size can be discovered using getWindowSize.
Closedoccurs when the window is closed.
show/hide Instances
maybeGetWindowEvent :: Window -> IO (Maybe Event)
Return a pending eventin the window, if any.
getWindowEvent :: Window -> IO Event
Wait for the next event in the window.
Time
Word32
getWindowTick :: Window -> IO ()
Wait for the next tick event from the timer on the given window.
timeGetTime :: IO Word32
The current time of day (in milliseconds).
word32ToInt :: Word32 -> Int
An obsolete special case of fromIntegral.
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