Renders the drawing as PNG or SVG, depending on the file extension.

Argument to coordinateSystem to pick zero location and axis direction.

Choose a coordinate system.

Render pictures for Haddock with doctests. Nomenclature: the FilePath for Foo.Bar.Baz is Foo/Bar/Baz/pic_name.svg.

Prints status information about the generated file so that doctests fail when the file contents change. Inspect the new output and update the output if the result is OK.

Vec2-friendly version of Cairo’s moveTo.

Vec2-friendly version of Cairo’s lineTo.

Sketch a shape that can then be made visible by drawing functions such as stroke or fill.

For sketching arrows.

Circles are not an instance of Transform, because e.g. shearing a circle yields an Ellipse. To transform circles, convert them to an ellipse first with toEllipse.

sketch a cross like ×. Sometimes useful to decorate a line with for e.g. strikethrough effects, or to contrast the o in tic tac toe.

When drawn with the same radius, it combines to ⨂ with a Circle.

Sketch part of a circle.

Sketch part of a circle.

American English type synonym

American English type synonym

Anything we can instruct Cairo to set its color to.

Temporarily draw using a different composition operator, such as OperatorClear to delete part of an image.

Open a new Cairo scope to allow local parameter changes. When the scope closes, the parameters are reset. Cairo documentation hides what actually is in the parameter state remarkably well; the state thus includes (source):

• Drawing operator (withOperator)
• Tolerance (setTolerance)
• Antialiasing (setAntialias)
• Line style (setLineWidth, setLineCap, setLineJoin, setMiterLimit, setDash)
• Fill rule (setFillRule)
• Font face, scaling, options
• Clipping (clip)
• Pattern (includes colors/setColor, gradients/withLinearPattern etc.)
• Tranformation matrix (translate etc.)

For example, we can paint the first block with a wide style, the second one dashed, and afterwards fall back to the implicit defaults:

>>> :{
haddockRender "Draw/cairoScope.svg" 200 40 $ \_ -> do
    let line = Line (Vec2 10 0) (Vec2 190 0)
    cairoScope $ do
        C.translate 0 30
        setLineWidth 3
        setColor (mma 1)
        sketch line
        stroke
    cairoScope $ do
        C.translate 0 20
        setDash [5,3] 0
        setColor (mma 2)
        sketch line
        stroke
    C.translate 0 10
    sketch line
    stroke
:}
Generated file: size 2KB, crc32: 0x2d7bee90

Render something as a group, as in encapsulate it in pushGroup and popGroupToSource. This function semantically includes a call cairoScope.

grouped is commonly used to avoid a less transparent area when overlapping two transparent areas.

The naive way has the intersection of the two circles darker,

do
    setSourceRGBA 0 0 0 0.5
    sketch (Circle (Vec2 0 0) 10)
    fill
    sketch (Circle (Vec2 7 0) 10)
    fill

On the other hand this will have the combination of the entire combined shape drawn with 0.5 alpha:

grouped (paintWithAlpha 0.5) $ do
    setSourceRGBA 0 0 0 1
    sketch (Circle (Vec2 0 0) 10)
    fill
    sketch (Circle (Vec2 7 0) 10)
    fill

Draw a caresian coordinate system in range (x,x') (y,y'). Very useful for prototyping.

(image code)

Like cartesianCoordinateSystem, but with polar coordinates.

(image code)

>>> :{
haddockRender "Draw/radialCoordinateSystem.svg" 250 250 $ \_ -> do
    C.translate 50 50
    radialCoordinateSystem def
:}
Generated file: size 26KB, crc32: 0x9b68b36

Translate between Cairo and our matrix representation for transformations.

Cairo does its transformation in inverse: we transform the geometry, Cairo transforms the canvas. fromCairoMatrix and toCairoMatrix translate between the worlds, so that conceptually both of these yield the same output:

trafo :: Transformation

sketch (Transform trafo geometry)
--
transform (fromCairoMatrix trafo) >> sketch geometry

Note that Cairo’s transform does more than just moving around lines: it also scales other properties such as line width, so the pictures described above might have some differences.

Useful Cairo functions for working with this are

transform :: Matrix -> Render ()
setMatrix :: Matrix -> Render ()
getMatrix :: Render Matrix

See fromCairoMatrix’ documentation, of which toCairoMatrix is the inverse.

for_ is traverse_ with its arguments flipped. For a version that doesn't ignore the results see for. This is forM_ generalised to Applicative actions.

for_ is just like forM_, but generalised to Applicative actions.

Examples

>>> for_ [1..4] print
1
2
3
4