SDL.Cairo.Canvas

This module defines the Canvas monad, which is a convenience wrapper around the underlying Cairo rendering and can be used with the same textures created by createCairoTexture. You can also mix both, if the need arises.

The Canvas API imitates most of the drawing functions of the Processing language. See http://processing.org/reference for comparison. While having the Processing spirit, this module does not aim for a perfect mapping and deviates where necessary or appropriate. Nevertheless most Processing examples should be trivial to port to the Canvas API. Example:

import SDL
import Linear.V2 (V2(..))
import SDL.Cairo
import SDL.Cairo.Canvas

main :: IO ()
main = do
  initialize [InitEverything]
  window <- createWindow "SDL2 Cairo Canvas" defaultWindow
  renderer <- createRenderer window (-1) defaultRenderer
  texture <- createCairoTexture' renderer window

  withCanvas texture $ do
    background $ gray 102
    fill $ red 255 !@ 128
    noStroke
    rect $ D 200 200 100 100
    stroke $ green 255 !@ 128
    fill $ blue 255 !@ 128
    rect $ D 250 250 100 100
    triangle (V2 400 300) (V2 350 400) (V2 400 400)

  copy renderer texture Nothing Nothing
  present renderer
  delay 5000

Entry point

data Canvas a

wrapper around the Cairo Render monad, providing a Processing-style API

Instances

Monad Canvas

Functor Canvas

Applicative Canvas

MonadIO Canvas

withCanvas :: Texture -> Canvas a -> IO a

draw on a SDL texture using the Canvas monad

getCanvasSize :: Canvas (V2 Double)

get size of the canvas (Processing: width(), height())

renderCairo :: Render () -> Canvas ()

execute a raw Cairo Render action

Color and Style

type Color = V4 Byte

RGBA Color is just a byte vector. Colors can be added, subtracted, etc.

type Byte = Word8

gray :: Byte -> Color

create opaque gray color

red :: Byte -> Color

create opaque red color

green :: Byte -> Color

create opaque green color

blue :: Byte -> Color

create opaque blue color

rgb :: Byte -> Byte -> Byte -> Color

create opaque mixed color

(!@) :: Color -> Byte -> Color

set transparency of color (half red would be: red 255 !@ 128)

stroke :: Color -> Canvas ()

set current stroke color

fill :: Color -> Canvas ()

set current fill color

noStroke :: Canvas ()

disable stroke (-> shapes without borders!), reenabled by using stroke

noFill :: Canvas ()

disable fill (-> shapes are not filled!), reenabled by using fill

strokeWeight :: Double -> Canvas ()

set line width for shape borders etc.

strokeJoin :: LineJoin -> Canvas ()

set the style of connections between lines of shapes

strokeCap :: LineCap -> Canvas ()

set the style of the line caps

Coordinates

data Dim

position and size representation (X Y W H)

Constructors

D Double Double Double Double

Instances

Eq Dim

Show Dim

toD :: V2 Double -> V2 Double -> Dim

create dimensions from position and size vector

centered :: Dim -> Dim

takes dimensions with centered position, returns normalized (left corner)

corners :: Dim -> Dim

takes dimensions with bottom-right corner instead of size, returns normalized (with size)

Primitives

background :: Color -> Canvas ()

clear the canvas with given color

point :: V2 Double -> Canvas ()

draw a point with stroke color (cairo emulates this with 1x1 rects!)

line :: V2 Double -> V2 Double -> Canvas ()

draw a line between two points with stroke color

triangle :: V2 Double -> V2 Double -> V2 Double -> Canvas ()

draw a triangle connecting three points

rect :: Dim -> Canvas ()

draw a rectangle

polygon :: [V2 Double] -> Canvas ()

draw a polygon connecting given points (equivalent to shape (ShapeRegular True))

shape :: ShapeMode -> [V2 Double] -> Canvas ()

draw shape along a given path using given ShapeMode. (Processing: beginShape(),vertex(),endShape())

data ShapeMode

Shape mode to use

Constructors

ShapeRegular Bool

regular path. flag decides whether the first and last point are connected

ShapePoints

just draw the points, no lines

ShapeLines

interpret points as pairs, draw lines

ShapeTriangles

interpret points as triples, draw triangles

ShapeTriangleStrip

draw triangle for every neighborhood of 3 points

ShapeTriangleFan

fix first point, draw triangles with every neighboring pair and first point

Instances

Eq ShapeMode

Show ShapeMode

Arcs and Curves

circle :: V2 Double -> Double -> Canvas ()

draw circle: circle leftCorner diameter

circle' :: V2 Double -> Double -> Canvas ()

draw circle: circle centerPoint diameter

arc :: Dim -> Double -> Double -> Canvas ()

draw arc: arc dimensions startAngle endAngle

ellipse :: Dim -> Canvas ()

draw ellipse

bezier :: V2 Double -> V2 Double -> V2 Double -> V2 Double -> Canvas ()

draw cubic bezier spline: bezier fstAnchor fstControl sndControl sndAnchor

bezierQ :: V2 Double -> V2 Double -> V2 Double -> Canvas ()

draw quadratic bezier spline: bezier fstAnchor control sndAnchor

Transformations

resetMatrix :: Canvas ()

replace current matrix with identity

pushMatrix :: Canvas ()

push current matrix onto the stack

popMatrix :: Canvas ()

pop a matrix

translate :: V2 Double -> Canvas ()

translate coordinate system

rotate :: Double -> Canvas ()

rotate coordinate system

scale :: V2 Double -> Canvas ()

scale coordinate system

Images

data Image

createImage :: V2 Int -> Canvas Image

create a new empty image of given size

loadImagePNG :: FilePath -> Canvas Image

load a PNG image from given path.

saveImagePNG :: Image -> FilePath -> Canvas ()

Save an image as PNG to given file path

image :: Image -> V2 Double -> Canvas ()

Render complete image on given coordinates

image' :: Image -> Dim -> Canvas ()

Render complete image inside given dimensions

blend :: Operator -> Image -> Dim -> Dim -> Canvas ()

Copy given part of image to given part of screen, using given blending operator and resizing when necessary. Use OperatorSource to copy without blending effects. (Processing: copy(),blend())

grab :: Dim -> Canvas Image

get a copy of the image from current window (Processing: get())

Text

data Font

Font definition

Constructors

Font

Fields

fontFace :: String

fontSize :: Double

fontBold :: Bool

fontItalic :: Bool

Instances

Eq Font

Show Font

textFont :: Font -> Canvas ()

set current font for text rendering

textSize :: String -> Canvas (V2 Double)

get the size of the text when rendered in current font

text :: String -> V2 Double -> Canvas ()

render text left-aligned (coordinate is top-left corner)

textC :: String -> V2 Double -> Canvas ()

render text centered (coordinate is central)

textR :: String -> V2 Double -> Canvas ()

render text right-aligned (coordinate is top-right corner)

Math

mapRange :: Double -> (Double, Double) -> (Double, Double) -> Double

map a value from one range onto another

radians :: Double -> Double

convert degrees to radians

degrees :: Double -> Double

convert radians to degrees

Misc

randomSeed :: Int -> Canvas ()

set new random seed

random :: Random a => (a, a) -> Canvas a

get new random number

getTime :: IO Time

get current system time. Use the Time accessors for specific components. (Processing: year(),month(),day(),hour(),minute(),second())

data Time

date and time as returned by getTime

Constructors

Time

Fields

year :: Int

month :: Int

day :: Int

hour :: Int

minute :: Int

second :: Int

Instances

Eq Time

Show Time

module Graphics.Rendering.Cairo