diagrams / diagrams-svg

An SVG backend for diagrams

diagrams-svg )

diagrams-svg is a an SVG backend for diagrams. Diagrams is a powerful, flexible, declarative domain-specific language for creating vector graphics, using the Haskell programming language.

diagrams-svg is the default out-of-the box backend that comes with the diagrams framework, and supports most features defined in diagrams-lib.

Installation

cabal update && cabal install diagrams-svg

Usage

A simple example that uses diagrams-svg to draw a square.

import Diagrams.Prelude
import Diagrams.Backend.SVG.CmdLine

b1 :: Diagram B
b1 = square 20 # lw 0.002

main = mainWith (pad 1.1 b1)

Save this to file named Square.hs and compile this program:

ghc --make Square.hs

This will generate an executable which, when run produces an SVG file. Run the executable with the --help option to find out more about how to call it.

$ ./Square --help
./Square

Usage: ./Square [-w|--width WIDTH] [-h|--height HEIGHT] [-o|--output OUTPUT] [--loop] [-s|--src ARG] [-i|--interval INTERVAL]
  Command-line diagram generation.

Available options:
  -?,--help                Show this help text
  -w,--width WIDTH         Desired WIDTH of the output image
  -h,--height HEIGHT       Desired HEIGHT of the output image
  -o,--output OUTPUT       OUTPUT file
  -l,--loop                Run in a self-recompiling loop
  -s,--src ARG             Source file to watch
  -i,--interval INTERVAL   When running in a loop, check for changes every INTERVAL seconds.
  -p,--pretty              Pretty print the SVG output

You must pass an output file name with a .svg extension to generate the SVG file.

$ ./Square -o square.svg

The command above generates the SVG file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
    "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" version="1.1" width="22.0" height="22.0" viewBox="0 0 22 22">
  <g>
    <g stroke="rgb(0,0,0)" stroke-opacity="1.0" fill="rgb(0,0,0)" fill-opacity="0.0" stroke-width="2.0e-3">
       <path d="M 21.0,21.0 l -2.220446049250313e-15,-20.0 h -20.0 l -2.220446049250313e-15,20.0 Z" />
    </g>
  </g>
</svg>

diagrams-svg's Issues

Support hyperlinks

See the discussion here:

https://groups.google.com/forum/#!topic/diagrams-discuss/YBiZmSCBQLU

Font size not applied properly in composite diagram

Applying fontSize to a composite diagram doesn't render properly:

rightSize = square 3 <> text "hi" # fontSizeL 2
wrongSize = (square 3 <> text "hi") # fontSizeL 2

Inspecting the SVG output shows the correct size is applied in an outer group but the Recommended size is used in an inner group and that's what gets shown. I suspect this is from the recent changes to Measure. It doesn't happen in the rasterific or pgf backends.

Support for GHC-8.8

As far as I can tell, this is currently only blocked on

• svg-builder, which diagrams/svg-builder#10 takes care of

and

• diagrams-lib, for which there is diagrams/diagrams-lib#343 which needs to be improved though AFAICT.

implement text rendering

Why is the viewport rounded?

In https://github.com/diagrams/diagrams-svg/blob/master/src/Graphics/Rendering/SVG.hs#L95 the width and height are rounded, which results in a viewport that ever so slightly clips the diagram. Is there any reason to do this rounding, and not use the exact dimensions?

Implement line join attribute

SVG backend fills lines again

Consider:

dia = pentagon 1 # strokeLine # fc green

This should produce an empty pentagon, but it produces a green one.

I'm guessing this was introduced during the conversion to use RTree?

Switch to using blaze-svg combinators

Allow xml references

When I have a green circle and want to duplicate it to many translated positions, then the circle's svg source will get textually duplicated. When the duplicand has a lot of source this can get very verbose. Any chance to use xml references optionally to refer to the original?

implement line dashing

Put `clip path`, `gradients`, etc in defs tag.

Font family support

Applying SVG Attribute via SVGOptions' _svgDefinitions Fails

I'm trying to use renderPretty' with SVGOptions to apply the SVG attribute "xMinYMin" via _svgDefinitions.
It fails in version 1.3.1.4 due to a change to 'Maybe SvgM'

Gradient is not applied to text

Using a linear gradient to fill some text does not work.

This is specific for the SVG backend as it works for the rasterific backend. Here is a minimal working example:

{-# LANGUAGE NoMonomorphismRestriction #-}

import Diagrams.Prelude
import Diagrams.Backend.SVG.CmdLine

stops = mkStops [(gray, 0, 1), (white, 0.5, 1), (purple, 1, 1)]
gradient = mkLinearGradient stops ((-0.5) ^& 0) (0.5 ^& 0) GradPad

text1 :: Diagram B 
text1 = rect 20 8 <> text "Hello" # fontSize (local 4) # fillTexture  gradient

main = mainWith text1

Replacing GradPad with GradRepeat shows a gradient applied to the text though.

Implement clipping

Small floats are being rendered in exponential form and ignored

Anything below 0.1 gets written out in exponential form i.e: "1e-2". Appearantly svg cannot parse a float in that form ... at least for stroke width, and some other attributes.

Fill color needs to be explicitly specified for text nodes

diagrams-svg uses a transparent fill color by default. diagrams text primitives use only fills, and set the <stroke> attribute to none to get around some other rendering issues. This leads to a situation where if we do not set a fill color explicitly, a lot of times there is no visible output.

Line width not handled properly by some browsers

{-# LANGUAGE NoMonomorphismRestriction #-}

import Diagrams.Prelude
import Diagrams.Backend.SVG.CmdLine

illustrateBezier c0 c1 c2 c3 x2 x3
    = endpt  # translate x3
    <> l3a
    <> fromSegments [bezier3 c3 c0 x3, bezier3 c1 c2 x2]
  where
    dashed  = dashing [0.1,0.1] 0
    endpt   = circle 0.05 # fc red  # lw 0
    l3a     = fromOffsets [r2 (1, 2)] # translate (r2 (1, 1)) # dashed

x2      = r2 (3,-1) :: R2         -- endpoint
x3      = r2 (1, 1) :: R2         -- endpoint
[c0,c1,c2,c3,c4] = map r2 [(-1, -3), (1,2), (2,0), (-3,0), (-1, -2)]   -- control points

example = illustrateBezier c0 c1 c2 (-c2) x2 x3

main = defaultMain example

Replacing SVG.CmdLine by Cairo.CmdLine produces what I would expect but SVG gives extremely wide lines as you can see in the diagrams.

implement text attributes

Examples:

• font size
• font weight
• font slant

Drawing a circle produes a path and not a circle.

I'm doing the tutorial and the first example of drawing a circle produces an svg file which represents a circle as a path, instead of representing a circle as a circle element.

I would like to be leveraging the compactness of svg, and drawing a path for a circle seems to negate the inherent efficiency of the svg format.

(Viewing the circle in the browser the path of the circle is noticeably imperfect.)

feature idea: on mouseover support

i've noticed that svg's have an on mouseover operation that can be supported,
this might be worth supporting in diagrams-svg (would that entail adding it to blaze svg?)

i've not dug around to see what needs to be changed to add this (if feasible), but i figured that this might be interesting for other folks too, so I'm adding it here

Add function of type FilePath -> SizeSpec2D -> Diagram -> IO ()

That is, something you could just call from ghci or from within some other program to write out a diagram to a file, instead of creating a standalone executable with defaultMain.

(Note, something like this should probably go in diagrams-cairo as well.)

implement line cap

Implement fill rule

Transformation returned by adjustDia is flipped

https://github.com/diagrams/diagrams-svg/blob/master/src/Diagrams/Backend/SVG.hs#L260

While cargo-culting code from here to diagrams-reflex, I noticed that we flip the Diagram in adjustDia, but don't flip the Transformation.

Writing this down so I remember to get back to it.

Freezing does not appear to work with the SVG backend

(Reported by Derrick Lin, moved here from http://code.google.com/p/diagrams/issues/detail?id=89)

What steps will reproduce the problem?

1. Install diagrams with the SVG backend
2. Do the diagrams tutorial
3. Be puzzled when you hit the Freezing section

What is the expected output? What do you see instead?
"On the left is an untransformed circle drawn with a line 0.1 units thick. The next circle is a scaled version of the first: notice how the line thickness is the same. The third circle was produced by first freezing, then scaling the first circle, resulting in a line twice as thick. The last two circles illustrate a non-uniform scale applied to an unfrozen circle (which is drawn with a uniform line) and to a frozen one (in which the line gets thicker and thinner according to the non-uniform scale)."

Sadly the line thickness is the same between the frozen and unfrozen versions.

What version of the product are you using? On what operating system?
OSX Snow Leopard (10.6), newest diagrams (0.5).

Please provide any additional information below.
Discovered at hac-phi.

SVG backend doesn't fill loops if they occur in the same subtree as a line

It looks like #42 was a bit more subtle than I thought. See the last line of http://projects.haskell.org/diagrams/backend-tests/all-index.html .

The problem is that a style node may occur at the root of a subtree which contains both lines and loops. In that case it seems that the only possible solution is to actually split the style node and push fill attributes down until they are over a subtree which contains only loops.

In fact, perhaps we even ought to do this as a compilation pass, in diagrams-core. We could make sure that fill attributes are only ever at the root of subtrees containing all loops. Then backends wouldn't have to worry about it at all, but could simply issue a fill attribute when they see it.

Data type for command line options need to be exported

Data types for command line options need to be exported for the Mainable instance to be composed with other Mainable instances. There might be some other nice things to have like Default instances where applicable. Also didn't we merge the changes that let us remove CPP from CmdLine?

Font scaling uses "em" units.

I'm not sure why, but font-scale attributes have "em" units. This renders as expected for me in Chrome, but not in Inkscape. I think the Inkscape rendering makes more sense but I haven't thought it through completely. If I manually remove all the "em"s Chrome and Inkscape look the same.

Add README, documentation and generate documentation on Hackage

Option to not XML-escape text

It would be nice if there was an option to not XML-escape text, so that special characters could be used, as in alignedText 0 0 "Jack&Jill had 5−4 pancakes". Currently this renders as <text ...>Jack&amp;amp;Jill had 5&amp;minus;4 pancakes</text>.

I tracked down what happens to the string that is put into alignedText during rendering. Graphics.Rendering.SVG.renderText sends the string (in a Text object) to Graphics.SVG.Core.toElement, part of the svg-builder package, which runs it through Blaze.ByteString.Builder.Html.Utf8.fromHtmlEscapedString, which is the culprit.

I'm not sure what could be done to get around this. For now my workaround is to run the svg output through sed -i "s/\&/\&/g".

Support for <foreignObject>

It would be nice if diagrams-svg could generate svg files with <foreignObject> SVG elements. This would allow, among other things, for the embedding of MathJax and KaTeX content inside svg files.

SVG backend has broken text fusion

I just started playing with diagrams again, and it's pretty great!

However, I'm running into speed issues. I have an example project here. This thing builds up maybe 900 circles, and does some transformations on them.

It takes about 9 seconds to run on my machine, even with -O2. This is too slow for any kind of live coding experience, so I decided to do some profiling. The results are here:

COST CENTRE            MODULE                             SRC                                             %time %alloc  ticks     bytes

toText                 Graphics.Svg.Path                  src/Graphics/Svg/Path.hs:26:1-63                 19.3   24.7   2600 1931550016
fmap                   Linear.V2                          src/Linear/V2.hs:131:3-34                        12.8   12.1   1719 946285224
atParam                Diagrams.Segment                   src/Diagrams/Segment.hs:(232,3)-(236,18)         10.5   10.4   1411 813761968
getEnvelope.\          Diagrams.Segment                   src/Diagrams/Segment.hs:(295,5)-(301,36)         10.2    7.7   1376 600342736

and the cost centers:

                                                                                                                                                                                        individual      inherited
COST CENTRE                                                          MODULE                               SRC                                                      no.       entries  %time %alloc   %time %alloc  ticks     bytes

MAIN                                                                 MAIN                                 <built-in>                                               13590          0    0.0    0.0   100.0  100.0      2     67600
                   withTrail                                         Diagrams.Trail                       src/Diagrams/Trail.hs:811:1-54                           44663        924    0.0    0.0    21.6   30.1      0         0
                    withTrail'                                       Diagrams.Trail                       src/Diagrams/Trail.hs:(417,1)-(418,40)                   44664        924    0.0    0.0    21.6   30.1      1         0
                     renderTrail.renderLoop                          Graphics.Rendering.SVG               src/Graphics/Rendering/SVG.hs:(113,5)-(120,10)           44665        924    0.9    3.6    21.6   30.1    119 282848416
                      renderSeg                                      Graphics.Rendering.SVG               src/Graphics/Rendering/SVG.hs:(123,1)-(128,67)           44737      52234    0.0    0.0    20.4   26.3      5       240
                       cR                                            Graphics.Svg.Path                    src/Graphics/Svg/Path.hs:(68,1)-(70,53)                  44856      52230    1.2    1.7    20.3   26.3    160 133733280
                        toText                                       Graphics.Svg.Path                    src/Graphics/Svg/Path.hs:26:1-63                         44858     313380   19.1   24.6    19.1   24.6   2578 1918235944

Dang! Looks like text fusion is broken. The implementation of toText suggests why:

toText :: RealFloat a => a -> Text
toText = toStrict . toLazyText . formatRealFloat Fixed (Just 4)

formatRealFloat returns a Data.Text.Lazy.Builder, but then the builder is immediately forced. Later, every other function in this module just Text.concats them together! But all of these are strict texts! No wonder we're missing out on fusion and everything is allocating super hard!

The fix as best I can tell is to make toText return a Builder, and then replace each instance of T.concat in Graphics.SVG.Path with toStrict . toLazy . mconcat. Or better yet, to use this same builder all the way through the SVG generation.

diagrams-svg.cabal out of sync with core and lib

Build-depends: ... monoid-extras >= 0.2 && < 0.3 ...
but core and lib depend on ... monoid-extras >= 0.3 && < 0.4

Implement opacity

Add a workaround for the Chrome stroke-width 0 bug

Chromium has a bug which renders strokes when stroke attribute is set, even if stroke-width="0" is specified. Firefox and Safari render the SVG just fine.

http://code.google.com/p/chromium/issues/detail?id=15461

We should consider implementing a workaround, in which we check if the line width is not 0, and only then render the stroke related attributes.

diagrams-svg doesn't build under directory-1.2 (and hence GHC-7.6)

See http://haskell.1045720.n5.nabble.com/getModificationTime-and-directory-1-2-td5717458.html. Probably the right thing to do is to switch from ClockTime to UTCTime, and add some CPP directives to insert some additional code to do the conversion from ClockTime to UTCTime when compiling under older versions of directory.

Of course, the same change will be needed in diagrams-cairo, which once again points out the need for abstracting this looped recompilation stuff out into a separate package.

diagrams-svg-1.4.3.1 requires diagrams-lib-1.4.5

Building library for diagrams-svg-1.4.3.1..
[1 of 3] Compiling Graphics.Rendering.SVG ( src/Graphics/Rendering/SVG.hs, /codetmp/diagrams-lib/diagrams-svg-1.4.3.1/.dist-newstyle-trustee/c8310e23749e36eec7b572efa1ee26bc640a99c16cea4b4a6563693e59ba04f6bc1ac514dfcc29aceefe8838770cdde2c65732f9d953a21b8d805b61a78c45f9/build/x86_64-linux/ghc-9.0.1/diagrams-svg-1.4.3.1/noopt/build/Graphics/Rendering/SVG.o, /codetmp/diagrams-lib/diagrams-svg-1.4.3.1/.dist-newstyle-trustee/c8310e23749e36eec7b572efa1ee26bc640a99c16cea4b4a6563693e59ba04f6bc1ac514dfcc29aceefe8838770cdde2c65732f9d953a21b8d805b61a78c45f9/build/x86_64-linux/ghc-9.0.1/diagrams-svg-1.4.3.1/noopt/build/Graphics/Rendering/SVG.dyn_o )
[2 of 3] Compiling Diagrams.Backend.SVG ( src/Diagrams/Backend/SVG.hs, /codetmp/diagrams-lib/diagrams-svg-1.4.3.1/.dist-newstyle-trustee/c8310e23749e36eec7b572efa1ee26bc640a99c16cea4b4a6563693e59ba04f6bc1ac514dfcc29aceefe8838770cdde2c65732f9d953a21b8d805b61a78c45f9/build/x86_64-linux/ghc-9.0.1/diagrams-svg-1.4.3.1/noopt/build/Diagrams/Backend/SVG.o, /codetmp/diagrams-lib/diagrams-svg-1.4.3.1/.dist-newstyle-trustee/c8310e23749e36eec7b572efa1ee26bc640a99c16cea4b4a6563693e59ba04f6bc1ac514dfcc29aceefe8838770cdde2c65732f9d953a21b8d805b61a78c45f9/build/x86_64-linux/ghc-9.0.1/diagrams-svg-1.4.3.1/noopt/build/Diagrams/Backend/SVG.dyn_o )


src/Diagrams/Backend/SVG.hs:260:14: error:
    • No instance for (Eq (SizeSpec V2 n))
        arising from the first field of ‘SVGOptions’ (type ‘SizeSpec V2 n’)
      Possible fix:
        use a standalone 'deriving instance' declaration,
          so you can specify the instance context yourself
    • When deriving the instance for (Eq (Options SVG V2 n))
    |
260 |     deriving Eq

See also diagrams/diagrams-postscript#34

I made a corresponding revision: https://hackage.haskell.org/package/diagrams-svg-1.4.3.1/revisions/

Embedded font definitions

I'm trying to update Chart-diagrams to diagrams-svg-1.3, but I'm not sure how to deal with embedded font definitions. Previously, SVGFonts was used to produce some markup that was passed to the SVGOptions record via its second parameter. That parameter is now a list of Attributes. Is there a way to go from the output of makeSvgFont to something I can stuff into a value of type [Attribute]?

Lines should not be filled

See diagrams/diagrams-cairo#32, diagrams/diagrams-lib@d8d6006, and diagrams/diagrams-cairo@bfa5f89 .

Text alignment support

Currently alignment settings are just ignored.

implement image embedding

hackage release for ghc-7.10.1 compatability

It's the base-4.8 requirement

Embedding JPEG images without repacking

I wanted to embed JPEG images without repacking them (and thus losing quality) or using PNG (huge images). I ended up with taruti@9a9a911

That solves the issue by adding a new

loadImageSVG :: FilePath -> IO (Diagram SVG R2)

to Diagrams.Backend.SVG.

Using Embedded DImages does not work since that would imply repacking and a loss of quality.

Using External DImages does not work since SVG backend does not have IO and thus one cannot read the image data for the embed in the rendering function.

This requires a git version of diagrams-lib (at least 2014-06-23).

Create a new branch for using blaze-svg

clipping broken

Tested with diagrams-svg-1.1.0.4, test case:

import Diagrams.Prelude
import Diagrams.Backend.SVG.CmdLine (defaultMain)
-- import Diagrams.Backend.Cairo.CmdLine (defaultMain)

clipBy' p d = d # clipBy p # withEnvelope p

shape c = square 2 # fc c # clipBy' (circle 0.5)

main = defaultMain $
  ((shape red  ||| shape yellow)
   ===
   (shape blue ||| shape green)
  ) # bg white

Correct output with cairo backend, using -w 1024 -o bug.svg:

Bad output with svg backend, using -w 1024 -o bug.svg:

SVG converted to PNG using rsvg -w 128 bug.svg -o bug.png

$ rsvg --version
rsvg-convert version 2.36.1

Line width does not follow specification?

nand` in #haskell reports that lines look much different with SVG backend than with cairo. Need to look into this more carefully.

Improve Haddock documentation

See the diagrams-cairo Haddocks for an example. There needs to be a bunch more information about how to make use of the backend, since a lot of information is actually buried in type class instances.

Spaces not preserved in text

By default, SVG does not preserve spaces in text. This is explained in the SVG spec:

‘xml:space’ is an inheritable attribute which can have one of two values:

'default'
(The initial/default value for ‘xml:space’.) When xml:space="default", the SVG user agent will do the following using a copy of the original character data content. First, it will remove all newline characters. Then it will convert all tab characters into space characters. Then, it will strip off all leading and trailing space characters. Then, all contiguous space characters will be consolidated.

'preserve'
When xml:space="preserve", the SVG user agent will do the following using a copy of the original character data content. It will convert all newline and tab characters into space characters. Then, it will draw all space characters, including leading, trailing and multiple contiguous space characters. Thus, when drawn with xml:space="preserve", the string "a b" (three spaces between "a" and "b") will produce a larger separation between "a" and "b" than "a b" (one space between "a" and "b").

I am working on a visual representation of Haskell rendered using diagrams (Glance), so of course I want to preserve spaces for string literals and comments.

As a workaround, I made a customized version of renderSVG that adds the attribute bindAttr XmlSpace_ (pack "preserve")

customRenderSVG outputFilename size = renderSVG' outputFilename svgOptions where
  -- This xml:space=preserve attribute preserves the spaces in the svg text.
  attributes = [bindAttr XmlSpace_ (pack "preserve")]
  svgOptions = SVGOptions size Nothing (pack "") attributes True

Embed SVG images

Right now it is possible to embed raster images (PNG, JPG, ...) but not other SVG images, although the SVG format itself supports embedded SVGs perfectly well, either via a nested <svg> tag or via an <image ... xlink:href="..."> tag (corresponding to the existing embedded/external distinction in diagrams).

While researching the best way to support this I'm realizing that diagrams' whole system of support for images is very much biased towards raster images. The SVG backend has an instance for DImage Embedded which definitely represents a raster image; it also has a special loadImageSVG which goes via ImageNative, but it also only supports PNG or JPEG, and ends up embedding them in a base64-encoded data URI. I think trying to shoehorn embedded SVG into this is going to be annoying.

Instead, I think the simplest approach is to simply add a new kind of embedded SVG primitive, specific to the SVG backend. It would be easiest to have it work via the xlink approach but inlining the contents of another SVG should be possible too.