Graphics.Rendering.Chart.Backend.Impl

This module provides the implementation details common to all ChartBackends.

Documentation

data ChartBackendInstr a where

The abstract drawing operation generated when using the the chart drawing API.

See the documentation of the different function for the correct semantics of each instruction:

• strokePath, fillPath
• drawText, textSize
• getPointAlignFn, getCoordAlignFn, AlignmentFns
• withTransform, withClipRegion
• withLineStyle, withFillStyle, withFontStyle

Constructors

StrokePath :: Path -> ChartBackendInstr ()

FillPath :: Path -> ChartBackendInstr ()

GetTextSize :: String -> ChartBackendInstr TextSize

DrawText :: Point -> String -> ChartBackendInstr ()

GetAlignments :: ChartBackendInstr AlignmentFns

WithTransform :: Matrix -> Program ChartBackendInstr a -> ChartBackendInstr a

WithFontStyle :: FontStyle -> Program ChartBackendInstr a -> ChartBackendInstr a

WithFillStyle :: FillStyle -> Program ChartBackendInstr a -> ChartBackendInstr a

WithLineStyle :: LineStyle -> Program ChartBackendInstr a -> ChartBackendInstr a

WithClipRegion :: Rect -> Program ChartBackendInstr a -> ChartBackendInstr a

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.

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.

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.

textSize :: String -> BackendProgram TextSize

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

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

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

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.

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.

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!

getPointAlignFn :: BackendProgram (Point -> Point)

Get the point alignment function

getCoordAlignFn :: BackendProgram (Point -> Point)

Get the coordinate alignment function