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|
{-# LANGUAGE GADTs #-}
-----------------------------------------------------------------------------
-- |
-- Module : Graphics.Rendering.Chart.Backend.Impl
-- Copyright : (c) Tim Docker 2014
-- License : BSD-style (see chart/COPYRIGHT)
--
-- This module provides the implementation details common to all 'ChartBackend's.
module Graphics.Rendering.Chart.Backend.Impl where
import Control.Monad.Reader
import Control.Monad.Operational
import Graphics.Rendering.Chart.Geometry
import Graphics.Rendering.Chart.Backend.Types
-- -----------------------------------------------------------------------
-- Rendering Backend Class
-- -----------------------------------------------------------------------
-- | 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'
--
data ChartBackendInstr a where
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
-- | 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 ChartBackend a = Program ChartBackendInstr a
-- | 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.
strokePath :: Path -> ChartBackend ()
strokePath p = singleton (StrokePath p)
-- | 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.
fillPath :: Path -> ChartBackend ()
fillPath p = singleton (FillPath p)
-- | Calculate a 'TextSize' object with rendering information
-- about the given string without actually rendering it.
textSize :: String -> ChartBackend TextSize
textSize text = singleton (GetTextSize text)
-- | Draw a single-line textual label anchored by the baseline (vertical)
-- left (horizontal) point. Uses the current 'FontStyle' for drawing.
drawText :: Point -> String -> ChartBackend ()
drawText p text = singleton (DrawText p text)
-- | Apply the given transformation in this local
-- environment when drawing. The given transformation
-- is applied after the current transformation. This
-- means both are combined.
withTransform :: Matrix -> ChartBackend a -> ChartBackend a
withTransform t p = singleton (WithTransform t p)
-- | 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.
withFontStyle :: FontStyle -> ChartBackend a -> ChartBackend a
withFontStyle fs p = singleton (WithFontStyle fs p)
-- | Use the given fill style in this local
-- environment when filling paths.
withFillStyle :: FillStyle -> ChartBackend a -> ChartBackend a
withFillStyle fs p = singleton (WithFillStyle fs p)
-- | Use the given line style in this local
-- environment when stroking paths.
withLineStyle :: LineStyle -> ChartBackend a -> ChartBackend a
withLineStyle ls p = singleton (WithLineStyle ls p)
-- | 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!
withClipRegion :: Rect -> ChartBackend a -> ChartBackend a
withClipRegion c p = singleton (WithClipRegion c p)
-- -----------------------------------------------------------------------
-- Rendering Utility Functions
-- -----------------------------------------------------------------------
-- | Get the point alignment function
getPointAlignFn :: ChartBackend (Point->Point)
getPointAlignFn = liftM afPointAlignFn (singleton GetAlignments)
-- | Get the coordinate alignment function
getCoordAlignFn :: ChartBackend (Point->Point)
getCoordAlignFn = liftM afCoordAlignFn (singleton GetAlignments)
|
