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Graphics.Rendering.Chart.Backend

Contents

The backend Monad
Backend Operations
Backend Helpers
Text Metrics
Line Types
Fill Types
Font and Text Types

Description

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

Synopsis

The backend Monad

type ChartBackend a = Program ChartBackendInstr aSource

A ChartBackend 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.

type CRender a = ChartBackend aSource

Deprecated: Use the new name ChartBackend!

Alias so the old name for rendering code still works.

Backend Operations

fillPath :: Path -> ChartBackend ()Source

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 -> ChartBackend ()Source

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 -> ChartBackend ()Source

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

textSize :: String -> ChartBackend TextSize Source

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

withTransform :: Matrix -> ChartBackend a -> ChartBackend aSource

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 -> ChartBackend a -> ChartBackend aSource

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 -> ChartBackend a -> ChartBackend aSource

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 -> ChartBackend a -> ChartBackend aSource

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

withLineStyle :: LineStyle -> ChartBackend a -> ChartBackend aSource

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

Backend Helpers

getPointAlignFn :: ChartBackend (Point -> Point)Source

Get the point alignment function

getCoordAlignFn :: ChartBackend (Point -> Point)Source

Get the coordinate alignment function

Text Metrics

data TextSize Source

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
Show TextSize

Line Types

data LineCap Source

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
Ord LineCap
Show LineCap

data LineJoin Source

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
Ord LineJoin
Show LineJoin

data LineStyle Source

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
Show LineStyle
Default LineStyle	The default line style.

line_width :: Lens' LineStyle Double Source

line_color :: Lens' LineStyle (AlphaColour Double)Source

line_dashes :: Lens' LineStyle [Double]Source

line_cap :: Lens' LineStyle LineCap Source

line_join :: Lens' LineStyle LineJoin Source

Fill Types

newtype FillStyle Source

Abstract data type for a fill style.

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

Constructors

FillStyleSolid
Fields _fill_colour :: AlphaColour Double

Instances

Eq FillStyle
Show FillStyle
Default FillStyle	The default fill style.

Font and Text Types

data FontWeight Source

The possible weights of a font.

Constructors

FontWeightNormal	Normal font style without weight.
FontWeightBold	Bold font.

Instances

Eq FontWeight
Ord FontWeight
Show FontWeight
Default FontWeight	The default font weight.

data FontSlant Source

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
Ord FontSlant
Show FontSlant
Default FontSlant	The default font slant.

data FontStyle Source

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
Show FontStyle
Default FontStyle	The default font style.

defaultFontStyle :: FontStyle Source

Deprecated: Use the according Data.Default instance!

The default font style.

data HTextAnchor Source

Possible horizontal anchor points for text.

Constructors

HTA_Left
HTA_Centre
HTA_Right

Instances

Eq HTextAnchor
Ord HTextAnchor
Show HTextAnchor

data VTextAnchor Source

Possible vertical anchor points for text.

Constructors

VTA_Top
VTA_Centre
VTA_Bottom
VTA_BaseLine

Instances

Eq VTextAnchor
Ord VTextAnchor
Show VTextAnchor

font_name :: Lens' FontStyle String Source

font_size :: Lens' FontStyle Double Source

font_slant :: Lens' FontStyle FontSlant Source

font_weight :: Lens' FontStyle FontWeight Source

font_color :: Lens' FontStyle (AlphaColour Double)Source

type AlignmentFn = Point -> Point Source

A function to align points for a certain rendering device.

data AlignmentFns Source

Holds the point and coordinate alignment function.

vectorAlignmentFns :: AlignmentFns Source

Alignment to render good on vector based graphics.

bitmapAlignmentFns :: AlignmentFns Source

Alignment to render good on raster based graphics.