lambda-canvas-0.1: Educational drawing canvas for FP explorers.

Safe HaskellSafe-Infered

Graphics.LambdaCanvas

Contents

Synopsis

Drawing types

data PrimitiveMode

Specification of the way the vertices given during renderPrimitive are interpreted. In the description of the constructors, n is an integer count starting at one, and N is the total number of vertices specified.

Constructors

Points

Treats each vertex as a single point. Vertex n defines point n. N points are drawn.

Lines

Treats each pair of vertices as an independent line segment. Vertices 2n-1 and 2n define line n. N/2 lines are drawn.

LineLoop

Draws a connected group of line segments from the first vertex to the last, then back to the first. Vertices n and n+1 define line n. The last line, however, is defined by vertices N and 1. N lines are drawn.

LineStrip

Draws a connected group of line segments from the first vertex to the last. Vertices n and n+1 define line n. N-1 lines are drawn.

Triangles

Treats each triplet of vertices as an independent triangle. Vertices 3n-2, 3n-1, and 3n define triangle n. N\3/ triangles are drawn.

TriangleStrip

Draws a connected group of triangles. One triangle is defined for each vertex presented after the first two vertices. For odd n, vertices n, n+1, and n+2 define triangle n. For even n, vertices n+1, n, and n+2 define triangle n. N-2 triangles are drawn.

TriangleFan

Draws a connected group of triangles. One triangle is defined for each vertex presented after the first two vertices. Vertices 1, n+1, and n+2 define triangle n. N-2 triangles are drawn.

Quads

Treats each group of four vertices as an independent quadrilateral. Vertices 4n-3, 4n-2, 4n-1, and 4n define quadrilateral n. N/4 quadrilaterals are drawn.

QuadStrip

Draws a connected group of quadrilaterals. One quadrilateral is defined for each pair of vertices presented after the first pair. Vertices 2n-1, 2n, 2n+2, and 2n+1 define quadrilateral n. N/2-1 quadrilaterals are drawn. Note that the order in which vertices are used to construct a quadrilateral from strip data is different from that used with independent data.

Polygon

Draws a single, convex polygon. Vertices 1 through N define this polygon.

Drawing functions

animate :: String -> (POSIXTime -> IO ()) -> IO ()Source

Create a canvas suitable for animation. The drawing block is invoked on each redisplay and is passed the current timestamp.

draw :: String -> IO () -> IO ()Source

Create a canvas suitable for drawing a static picture. The drawing block is invoked on each redisplay.

put :: PrimitiveMode -> [Point] -> IO ()Source

Draw a primitive from a set of a vertices on screen.

Utility functions

stepOf :: Num a => Integer -> POSIXTime -> aSource

Given an amount of steps and a timestamp, calculate current step number. Step numbers begin with 0.