Graphics.Rendering.Chart.Backend

This module provides the API for drawing operations abstracted to drive arbitrary Backend.

The backend Monad

type BackendProgram a = Program ChartBackendInstr a

A BackendProgram provides the capability to render a chart somewhere.

The coordinate system of the backend has its initial origin (0,0) in the top left corner of the drawing plane. The x-axis points towards the top right corner and the y-axis points towards the bottom left corner. The unit used by coordinates, the font size, and lengths is the always the same, but depends on the backend. All angles are measured in radians.

The line, fill and font style are set to their default values initially.

Information about the semantics of the instructions can be found in the documentation of ChartBackendInstr.

Backend Operations

fillPath :: Path -> BackendProgram ()

Fill the given path using the current FillStyle. The given path will be closed prior to filling. This function does not perform alignment operations on the path. See Path for the exact semantic of paths.

strokePath :: Path -> BackendProgram ()

Stroke the outline of the given path using the current LineStyle. This function does not perform alignment operations on the path. See Path for the exact semantic of paths.

drawText :: Point -> String -> BackendProgram ()

Draw a single-line textual label anchored by the baseline (vertical) left (horizontal) point. Uses the current FontStyle for drawing.

textSize :: String -> BackendProgram TextSize

Calculate a TextSize object with rendering information about the given string without actually rendering it.

withTransform :: Matrix -> BackendProgram a -> BackendProgram a

Apply the given transformation in this local environment when drawing. The given transformation is applied after the current transformation. This means both are combined.

withClipRegion :: Rect -> BackendProgram a -> BackendProgram a

Use the given clipping rectangle when drawing in this local environment. The new clipping region is intersected with the given clip region. You cannot escape the clip!

withFontStyle :: FontStyle -> BackendProgram a -> BackendProgram a

Use the given font style in this local environment when drawing text.

An implementing backend is expected to guarentee to support the following font families: serif, sans-serif and monospace;

If the backend is not able to find or load a given font it is required to fall back to a custom fail-safe font and use it instead.

withFillStyle :: FillStyle -> BackendProgram a -> BackendProgram a

Use the given fill style in this local environment when filling paths.

withLineStyle :: LineStyle -> BackendProgram a -> BackendProgram a

Use the given line style in this local environment when stroking paths.

Backend Helpers

getPointAlignFn :: BackendProgram (Point -> Point)

Get the point alignment function

getCoordAlignFn :: BackendProgram (Point -> Point)

Get the coordinate alignment function

Text Metrics

data TextSize

Text metrics returned by textSize.

Constructors

TextSize

Fields

• textSizeWidth :: Double

  The total width of the text.

• textSizeAscent :: Double

  The ascent or space above the baseline.

• textSizeDescent :: Double

  The decent or space below the baseline.

• textSizeYBearing :: Double

  The Y bearing.

• textSizeHeight :: Double

  The total height of the text.

Instances

Eq TextSize

Methods

(==) :: TextSize -> TextSize -> Bool

(/=) :: TextSize -> TextSize -> Bool

Show TextSize

Methods

showsPrec :: Int -> TextSize -> ShowS

show :: TextSize -> String

showList :: [TextSize] -> ShowS

Line Types

data LineCap

The different supported line ends.

Constructors

LineCapButt

Just cut the line straight.

LineCapRound

Make a rounded line end.

LineCapSquare

Make a square that ends the line.

Instances

Eq LineCap

Methods

(==) :: LineCap -> LineCap -> Bool

(/=) :: LineCap -> LineCap -> Bool

Ord LineCap

Methods

compare :: LineCap -> LineCap -> Ordering

(<) :: LineCap -> LineCap -> Bool

(<=) :: LineCap -> LineCap -> Bool

(>) :: LineCap -> LineCap -> Bool

(>=) :: LineCap -> LineCap -> Bool

max :: LineCap -> LineCap -> LineCap

min :: LineCap -> LineCap -> LineCap

Show LineCap

Methods

showsPrec :: Int -> LineCap -> ShowS

show :: LineCap -> String

showList :: [LineCap] -> ShowS

data LineJoin

The different supported ways to join line ends.

Constructors

LineJoinMiter

Extends the outline until they meet each other.

LineJoinRound

Draw a circle fragment to connet line end.

LineJoinBevel

Like miter, but cuts it off if a certain threshold is exceeded.

Instances

Eq LineJoin

Methods

(==) :: LineJoin -> LineJoin -> Bool

(/=) :: LineJoin -> LineJoin -> Bool

Ord LineJoin

Methods

compare :: LineJoin -> LineJoin -> Ordering

(<) :: LineJoin -> LineJoin -> Bool

(<=) :: LineJoin -> LineJoin -> Bool

(>) :: LineJoin -> LineJoin -> Bool

(>=) :: LineJoin -> LineJoin -> Bool

max :: LineJoin -> LineJoin -> LineJoin

min :: LineJoin -> LineJoin -> LineJoin

Show LineJoin

Methods

showsPrec :: Int -> LineJoin -> ShowS

show :: LineJoin -> String

showList :: [LineJoin] -> ShowS

data LineStyle

Data type for the style of a line.

Constructors

LineStyle

Fields

• _line_width :: Double

  The thickness of a line in device units.

• _line_color :: AlphaColour Double

  The color of a line.

• _line_dashes :: [Double]

  The dash pattern. Every value at a even index gives a dash width and every value at a odd index gives a gap width in device units.

• _line_cap :: LineCap

  How to end a line.

• _line_join :: LineJoin

  How to connect two lines.

Instances

Eq LineStyle

Methods

(==) :: LineStyle -> LineStyle -> Bool

(/=) :: LineStyle -> LineStyle -> Bool

Show LineStyle

Methods

showsPrec :: Int -> LineStyle -> ShowS

show :: LineStyle -> String

showList :: [LineStyle] -> ShowS

Default LineStyle

The default line style.

Methods

def :: LineStyle

line_width :: Lens' LineStyle Double

line_color :: Lens' LineStyle (AlphaColour Double)

line_dashes :: Lens' LineStyle [Double]

line_cap :: Lens' LineStyle LineCap

line_join :: Lens' LineStyle LineJoin

Fill Types

newtype FillStyle

Abstract data type for a fill style.

The contained action sets the required fill style in the rendering state.

Constructors

FillStyleSolid

Fields

• _fill_color :: AlphaColour Double

Instances

Eq FillStyle

Methods

(==) :: FillStyle -> FillStyle -> Bool

(/=) :: FillStyle -> FillStyle -> Bool

Show FillStyle

Methods

showsPrec :: Int -> FillStyle -> ShowS

show :: FillStyle -> String

showList :: [FillStyle] -> ShowS

Default FillStyle

The default fill style.

Methods

def :: FillStyle

Font and Text Types

data FontWeight

The possible weights of a font.

Constructors

FontWeightNormal

Normal font style without weight.

FontWeightBold

Bold font.

Instances

Eq FontWeight

Methods

(==) :: FontWeight -> FontWeight -> Bool

(/=) :: FontWeight -> FontWeight -> Bool

Ord FontWeight

Methods

compare :: FontWeight -> FontWeight -> Ordering

(<) :: FontWeight -> FontWeight -> Bool

(<=) :: FontWeight -> FontWeight -> Bool

(>) :: FontWeight -> FontWeight -> Bool

(>=) :: FontWeight -> FontWeight -> Bool

max :: FontWeight -> FontWeight -> FontWeight

min :: FontWeight -> FontWeight -> FontWeight

Show FontWeight

Methods

showsPrec :: Int -> FontWeight -> ShowS

show :: FontWeight -> String

showList :: [FontWeight] -> ShowS

Default FontWeight

The default font weight.

Methods

def :: FontWeight

data FontSlant

The possible slants of a font.

Constructors

FontSlantNormal

Normal font style without slant.

FontSlantItalic

With a slight slant.

FontSlantOblique

With a greater slant.

Instances

Eq FontSlant

Methods

(==) :: FontSlant -> FontSlant -> Bool

(/=) :: FontSlant -> FontSlant -> Bool

Ord FontSlant

Methods

compare :: FontSlant -> FontSlant -> Ordering

(<) :: FontSlant -> FontSlant -> Bool

(<=) :: FontSlant -> FontSlant -> Bool

(>) :: FontSlant -> FontSlant -> Bool

(>=) :: FontSlant -> FontSlant -> Bool

max :: FontSlant -> FontSlant -> FontSlant

min :: FontSlant -> FontSlant -> FontSlant

Show FontSlant

Methods

showsPrec :: Int -> FontSlant -> ShowS

show :: FontSlant -> String

showList :: [FontSlant] -> ShowS

Default FontSlant

The default font slant.

Methods

def :: FontSlant

data FontStyle

Data type for a font.

Constructors

FontStyle

Fields

• _font_name :: String

  The font family or font face to use.

• _font_size :: Double

  The height of the rendered font in device coordinates.

• _font_slant :: FontSlant

  The slant to render with.

• _font_weight :: FontWeight

  The weight to render with.

• _font_color :: AlphaColour Double

  The color to render text with.

Instances

Eq FontStyle

Methods

(==) :: FontStyle -> FontStyle -> Bool

(/=) :: FontStyle -> FontStyle -> Bool

Show FontStyle

Methods

showsPrec :: Int -> FontStyle -> ShowS

show :: FontStyle -> String

showList :: [FontStyle] -> ShowS

Default FontStyle

The default font style.

Methods

def :: FontStyle

data HTextAnchor

Possible horizontal anchor points for text.

Constructors

HTA_Left

HTA_Centre

HTA_Right

Instances

Eq HTextAnchor

Methods

(==) :: HTextAnchor -> HTextAnchor -> Bool

(/=) :: HTextAnchor -> HTextAnchor -> Bool

Ord HTextAnchor

Methods

compare :: HTextAnchor -> HTextAnchor -> Ordering

(<) :: HTextAnchor -> HTextAnchor -> Bool

(<=) :: HTextAnchor -> HTextAnchor -> Bool

(>) :: HTextAnchor -> HTextAnchor -> Bool

(>=) :: HTextAnchor -> HTextAnchor -> Bool

max :: HTextAnchor -> HTextAnchor -> HTextAnchor

min :: HTextAnchor -> HTextAnchor -> HTextAnchor

Show HTextAnchor

Methods

showsPrec :: Int -> HTextAnchor -> ShowS

show :: HTextAnchor -> String

showList :: [HTextAnchor] -> ShowS

data VTextAnchor

Possible vertical anchor points for text.

Constructors

VTA_Top

VTA_Centre

VTA_Bottom

VTA_BaseLine

Instances

Eq VTextAnchor

Methods

(==) :: VTextAnchor -> VTextAnchor -> Bool

(/=) :: VTextAnchor -> VTextAnchor -> Bool

Ord VTextAnchor

Methods

compare :: VTextAnchor -> VTextAnchor -> Ordering

(<) :: VTextAnchor -> VTextAnchor -> Bool

(<=) :: VTextAnchor -> VTextAnchor -> Bool

(>) :: VTextAnchor -> VTextAnchor -> Bool

(>=) :: VTextAnchor -> VTextAnchor -> Bool

max :: VTextAnchor -> VTextAnchor -> VTextAnchor

min :: VTextAnchor -> VTextAnchor -> VTextAnchor

Show VTextAnchor

Methods

showsPrec :: Int -> VTextAnchor -> ShowS

show :: VTextAnchor -> String

showList :: [VTextAnchor] -> ShowS

font_name :: Lens' FontStyle String

font_size :: Lens' FontStyle Double

font_slant :: Lens' FontStyle FontSlant

font_weight :: Lens' FontStyle FontWeight

font_color :: Lens' FontStyle (AlphaColour Double)

type AlignmentFn = Point -> Point

A function to align points for a certain rendering device.

data AlignmentFns

Holds the point and coordinate alignment function.

vectorAlignmentFns :: AlignmentFns

Alignment to render on vector based graphics.

bitmapAlignmentFns :: AlignmentFns

Alignment to render on raster based graphics.