Graphics.UI.GIO.Canvas

Portability	portable
Stability	provisional
Maintainer	ka2_mail@yahoo.com

Contents

Canvas
Drawing primitives
Transform
Font metrics
Internal

Description

Widgets that can be (re)painted are an instance of the Paint class. By setting the paint attribute, a custom paint function can be specified. For example:

 do w <- window [paint =: mypaint]
    ...
 where
   mypaint canvas updateFrame updateAreas
     = do setCanvasPen canvas [color =: red]
          fillRect (rect (pt 10 10) (pt 20 20)) canvas
          setCanvasPen canvas [color =: blue, thickness =: 10]
          drawLine (pt 20 20) (pt 30 30) canvas

A paint function (of type PaintFunction) takes three arguments, the canvas (of type Canvas), the bounding rectangle of the update frame and all areas that need to be repainted.

Synopsis

data Canvas

data CanvasPen

setCanvasPen :: Canvas -> [Prop CanvasPen] -> IO ()

getCanvasPen :: Canvas -> Attr CanvasPen a -> IO a

paintInBitmap :: Bitmap -> Pen -> (Canvas -> IO a) -> IO a

drawPoint :: Point -> Canvas -> IO ()

drawString :: Point -> String -> Canvas -> IO ()

drawLine :: Point -> Point -> Canvas -> IO ()

drawPolyline :: [Point] -> Canvas -> IO ()

drawRect :: Rect -> Canvas -> IO ()

fillRect :: Rect -> Canvas -> IO ()

drawOval :: Rect -> Canvas -> IO ()

drawEllipse :: Point -> Int -> Int -> Canvas -> IO ()

drawCircle :: Point -> Int -> Canvas -> IO ()

fillOval :: Rect -> Canvas -> IO ()

fillEllipse :: Point -> Int -> Int -> Canvas -> IO ()

fillCircle :: Point -> Int -> Canvas -> IO ()

drawCurve :: Rect -> Float -> Float -> Canvas -> IO ()

drawArc :: Point -> Int -> Int -> Float -> Float -> Canvas -> IO ()

fillPie :: Point -> Int -> Int -> Float -> Float -> Canvas -> IO ()

drawPolygon :: [Point] -> Canvas -> IO ()

drawBitmap :: Point -> Bitmap -> Canvas -> IO ()

rotateCanvas :: Double -> Canvas -> IO ()

scaleCanvas :: Double -> Double -> Canvas -> IO ()

shearCanvas :: Double -> Double -> Canvas -> IO ()

translateCanvas :: Double -> Double -> Canvas -> IO ()

fontMetrics :: Font -> Attr Canvas FontMetrics

fontCharWidth :: Font -> Char -> Attr Canvas Int

fontStringWidth :: Font -> String -> Attr Canvas Int

canvasFontMetrics :: Attr Canvas FontMetrics

canvasFontCharWidth :: Char -> Attr Canvas Int

canvasFontStringWidth :: String -> Attr Canvas Int

withCanvas :: BufferMode -> Pen -> CanvasHandle -> (Canvas -> IO a) -> IO a

Canvas

data Canvas

A canvas is an area on which you can draw objects.

data CanvasPen

Instances

Drawn CanvasPen

HasFont CanvasPen

setCanvasPen :: Canvas -> [Prop CanvasPen] -> IO ()

getCanvasPen :: Canvas -> Attr CanvasPen a -> IO a

paintInBitmap :: Bitmap -> Pen -> (Canvas -> IO a) -> IO a

The paintInBitmap executes the given function with canvas associated with given Bitmap.

Drawing primitives

drawPoint :: Point -> Canvas -> IO ()

Draws a point at the specified location.

drawString :: Point -> String -> Canvas -> IO ()

Draws the specified text string at the specified location.

drawLine :: Point -> Point -> Canvas -> IO ()

Draws a line connecting the two points specified by coordinate pairs.

drawPolyline :: [Point] -> Canvas -> IO ()

Draws a series of line segments that connect an list of points.

drawRect :: Rect -> Canvas -> IO ()

Draws a rectangle specified by a Rect.

fillRect :: Rect -> Canvas -> IO ()

Fills the interior of a rectangle specified by a Rect.

drawOval :: Rect -> Canvas -> IO ()

Draws an ellipse specified by a bounding rectangle.

drawEllipse :: Point -> Int -> Int -> Canvas -> IO ()

Draw an ellipse specified by a center point and the x- and y radius.

drawCircle :: Point -> Int -> Canvas -> IO ()

Draw an circle specified by a center point and the radius.

fillOval :: Rect -> Canvas -> IO ()

Fills the interior of an ellipse defined by a bounding rectangle specified by a Rect.

fillEllipse :: Point -> Int -> Int -> Canvas -> IO ()

Fills the interior of an ellipse specified by a center point and the x- and y radius.

fillCircle :: Point -> Int -> Canvas -> IO ()

Fills the interior of a circle specified by a center point and the radius.

drawCurve :: Rect -> Float -> Float -> Canvas -> IO ()

Draws an curve representing a portion of an ellipse specified by a Rect. The Float type arguments specifies start and end angles in radians. The curve starts at an angle start continuing in clockwise direction to the ending angle end.

drawArc :: Point -> Int -> Int -> Float -> Float -> Canvas -> IO ()

Draw an arc. The expression (arc c rx ry start end [] canvas) draws a curve on the oval defined by the center point c, the x radius rx and the y radius ry. The curve starts at an angle start (in radians) continuing in clockwise direction to the ending angle end (in radians).

fillPie :: Point -> Int -> Int -> Float -> Float -> Canvas -> IO ()

Fills the interior of a pie section defined by an ellipse specified by a by a center point and the x- and y radius and two radial lines at angles start and end. The Float arguments specifies the angles.

drawPolygon :: [Point] -> Canvas -> IO ()

Draws a polygon defined by an list of points

drawBitmap :: Point -> Bitmap -> Canvas -> IO ()

Draws the specified Bitmap at the specified location.

Transform

rotateCanvas :: Double -> Canvas -> IO ()

Rotate the canvas clockwise with an angle in radians.

scaleCanvas :: Double -> Double -> Canvas -> IO ()

Scale the canvas with a horizontal and vertical factor.

shearCanvas :: Double -> Double -> Canvas -> IO ()

Shear the canvas in a horizontal and vertical direction.

translateCanvas :: Double -> Double -> Canvas -> IO ()

Translate (or move) the canvas in a horizontal and vertical direction.

Font metrics

fontMetrics :: Font -> Attr Canvas FontMetrics

The font metrics (read-only).

 do metrics <- get canvas (fontMetrics defaultFont)

fontCharWidth :: Font -> Char -> Attr Canvas Int

The width of a character in a certain font (read-only).

fontStringWidth :: Font -> String -> Attr Canvas Int

The width of a string in a certain font (read-only).

canvasFontMetrics :: Attr Canvas FontMetrics

The font metrics of the current drawing pencil (read-only).

canvasFontCharWidth :: Char -> Attr Canvas Int

The character width in the current pen font on a canvas (read-only).

 do em <- get canvas (canvasFontCharWidth 'm')

canvasFontStringWidth :: String -> Attr Canvas Int

The string width in the current pen font on a canvas (read-only).

Internal

withCanvas :: BufferMode -> Pen -> CanvasHandle -> (Canvas -> IO a) -> IO a

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