diagrams-cairo-0.6: Cairo backend for diagrams drawing EDSL

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This module provides convenience functions for querying information from cairo. In particular, this provides utilities for information about fonts, and creating text primitives with bounds based on the font being used. To render text with automatically determined envelopes, use textLineBounded, textLineBoundedIO, textVisualBounded, or textVisualBoundedIO.

Many of these functions take a Style R2 parameter, determining the style to apply to the text before rendering / querying information about the text. These Style R2 parameters can be created a variety of ways, but the most direct will likely be by applying style-transforming functions such as font, fontSize, fontSlant, and fontWeight to mempty. This works because there are instances of HasStyle and Monoid for Style v.



These create diagrams instantiated with extents-based envelopes

textLineBoundedIO :: Style R2 -> String -> IO (Diagram Cairo R2)Source

Creates text diagrams with their envelopes set such that using vcat . map (textLineBounded style) stacks them in the way that the font designer intended.

textVisualBoundedIO :: Style R2 -> String -> IO (Diagram Cairo R2)Source

Creates a text diagram with its envelope set to enclose the glyphs of the text, including leading (though not trailing) whitespace.


These are convenient unsafe variants of the above operations postfixed with "IO". They should be pretty well-behaved as the results just depend on the parameters and the font information (which ought to stay the same during a given execution).


Data Structures

data TextExtents Source

A more convenient data structure for the results of a text-extents query.




bearing :: R2
textSize :: R2
advance :: R2

data FontExtents Source

A more convenient data structure for the results of a font-extents query.




getTextExtents :: Style R2 -> String -> Render TextExtentsSource

Get the extents of a string of text, given a style to render it with.

getFontExtents :: Style R2 -> Render FontExtentsSource

Gets the intrinsic extents of a font.

getExtents :: Style R2 -> String -> Render (FontExtents, TextExtents)Source

Gets both the FontExtents and TextExtents of the string with the a particular style applied. This is more efficient than calling both getFontExtents and getTextExtents.

kerningCorrectionIO :: Style R2 -> Char -> Char -> IO DoubleSource

Queries the amount of horizontal offset that needs to be applied in order to position the second character properly, in the event that it is hcat-ed baselineText.


queryCairo :: Render a -> IO aSource

Executes a cairo action on a dummy, zero-size image surface, in order to query things like font information.

unsafeCairo :: Render a -> aSource

Unsafely invokes queryCairo.

cairoWithStyle :: Render a -> Style R2 -> Render aSource

Executes the given cairo action, with styling applied. This does not do all styling - just attributes that are processed by "cairoMiscStyle", which does clip, fill color, fill rule, and, importantly for this module, font face, style, and weight.