Diagrams/Dev/Migrate1.3
This page describes breaking API changes between diagrams 1.2 and 1.3, along with explanations of how to migrate to the new 1.3 API.
The 1.3 release includes a lot of new features and reorganization; there are surely to be breaking changes that we missed below. Please ask on the diagrams mailing list or IRC channel for help migrating to 1.3.
Contents
Linear
Diagrams has switched from vectorspace
to linear
for its linear algebra package. This makes many things nicer, and in particular allows diagrams to now be polymorphic over the underlying numeric type, potentially paving the way for things like automatic differentiation. It does, however, mean that many types are now slightly different.
The most obvious difference is there are now two type variables for the vector space: v
, which gives the space being worked in and n
, the number type used. v
now has kind * > *
, which means is takes some type (usually n
) and makes a concrete vector. Basically this means whenever you saw v
, replace it by v n
. So:

R2 > V2 Double

Point R2 (P2) > Point V2 Double (P2 Double)

Path R2 > Path V2 Double

Transformation R2 > Transformation V2 Double (T2 Double)

QDiagram b v m > QDiagram b v n m
The Diagram
alias has also changed. It no longer takes a vector space as a parameter; it simply uses the default space and number type for the backend parameter:
Diagram b = QDiagram b (V b) (N b) Any
where V b
is the default space and N b
is the default number type for backend b
. This means you should replace e.g.

Diagram Cairo R2 > Diagram Cairo
Scalar
also no longer exists; you should replace

Scalar > N
linear
’s functions are very similar to vectorspace
. The biggest difference is lerp
which is defined as
lerp alpha u v = alpha *^ u ^+^ (1  alpha) *^ v
This is the opposite way round to vectorspace
’s lerp.
Other changes from vectorspace
to linear
:

magnitude
>norm

magnitudeSq
>quadrance

negateV
>negated

normalized
>signorm
The last is particularly worth noting, since there is also a new normalized
function (which constructs Measure
values). So code which used normalized
, instead of yielding a "not in scope" error, will yield a type error, probably something along the lines of
Couldn't match type ‘Measured n0 n0’ with ‘V2 Double’
The old HasX
, HasY
and HasZ
classes have been replaced by linear’s R1
, R2
and R3
, but these have lenses of the same names (_x
, _y
, _z
) so you probably won't notice the difference.
Direction type
A new Direction
type has been added to Diagrams.Direction
. A Direction
is a vector that has forgot its magnitude. Certain functions including arc
and reflectAcross
have had their types moved from V2 Double
to Direction Double
to make it clear the magnitude has no impact.
arc
now takes a starting direction and an angle. arcCW
and arcCCW
give a clockwise or counter clockwise arc between two directions. For example, if you had
arc (0 @@ turn) (1/3 @@ turn)
you should replace it by
arc xDir (1/3 @@ turn)
As another example,
arc (1/3 @@ turn) (2/3 @@ turn)
can be replaced by either
arc (xDir # rotateBy (1/3)) (1/3 @@ turn)
or else something like
arc xDir (1/3 @@ turn) # rotateBy (1/3)
<code>angleBetween
is commutative (and always positive). We also introduced signedAngleBetween
which reflects an order to angles.
rotateAbout
used to rotate about a point in 2D; it now rotates about a line in 3D. The old rotateAbout
has been replaced by rotateAround
.
Measure changes
The internal representation of Measure
has now changed. The old constructors cannot be used anymore. Instead they have been replaced by:

Normalized > normalized
ornormalised

Local > local

Global > global

Output > output
SizeSpec
SizeSpec2D
is now SizeSpec V2 Double
and has moved to Diagrams.Size
. The resizing functions now work for any vector space. The constructors have been replaced with the following functions:

Dims > dims2D

Width > mkWidth

Height > mkHeight

Absolute > absolute
dims2D
, mkWidth
and mkHeight
are in Diagrams.TwoD.Size
.
mkSizeSpec
used to be specific to 2D; it is now generic over any vector space. Use mkSizeSpec2D
instead.
Names
The qualify with name operator (>)
has moved to (.>>)
to make room for lens's snoc operator (>)
(which now works on Line
s).
Transform isomorphisms
New transform isomorphisms transformed
, translated
, movedTo
, movedFrom
and rotated
have been added. These can be used with lens’s under
function (see Diagrams.Transform
for usage examples). The old under
has been renamed to underT
.
ToPath class
A new ToPath
class has been added. It takes pathlike things (like lines, loops, trails, paths) and converts them to a Path
.
This is very different from the TrailLike
class, which is polymorphic in it’s result. Because both these classes are polymorphic, you can’t produce something with the TrailLike
class and consume it with ToPath
without specifying the type in between.
Because stroke
now uses this class it can cause some ambiguity errors for old code. The old (less polymorphic) stroke
has moved to strokePath
(or strokeP
).
fsnotify for command line loop
The loop
option for diagrams command line generation uses fsnotify
to watch the source file for changes. This means it should now work on Windows.
Additionally it now works in sandboxes and has a cleaner terminal output.
diagramssvg
diagramssvg no longer depends on the blaze.svg package and instead uses lucidsvg.
The only difference that should affect diagrams code is that the
SVGOptions
record has changed from:
SVGOptions {_size :: SizeSpec2D, _svgDefinitions :: Maybe S.Svg}
to:
SVGOptions { _size :: SizeSpec V2 n, _svgDefinitions :: [Attribute], _idPrefix :: T.Text}
.
New features
Segment intersections have been added to Diagrams.TwoD.Segment
. Functions for intersection points of pathlike things are in Diagrams.TwoD.Path
.
There’s a function for finding the convex hull for a list of 2D points in Diagrams.TwoD.Points
.
Affine maps have been added to Diagrams.AffineMap
that can map between spaces. The Deformable
class has also been generalised to map between spaces. Helper functions have been added to Diagrams.ThreeD.Projection
for basic orthographic and perspective projections. These can’t be used on a Diagram
yet be can be used on pathlike things.
Some extra functions have been added to Diagrams.Model
to help visualise the Trace
and Envelope
of a diagram.
New Backends
PGF backend
PGF is tex a macro package for creating graphics. It’s the low level backend for TikZ.
The diagramspgf
backend supports most of diagrams’ features including paths, images (external and embedded), gradients (partial support) and text. It also includes an experimental functions for retrieving the size of the bounding boxes for text (including formulas). See the examples page for more details.
It uses texrunner
to produce PDF files and parse tex’s output. Latex, Context and plain Tex outputs are supported.
HTML5 backend
The diagramshtml5
backend supports most of diagrams’ features including paths, external images , gradients and text. It produces standalone javascript code.
SVGFonts
The most important functions for use in diagrams textSVG'
and testSVG_
have been move out of the ReadFont
module into the Text
module. You can usually just import Graphics.SVGFonts
and have all of the functions you need.
textSVG'
and friends now have the text as a separate argument, distinct from TextOptions
. So whereas before you might write:
textSVG' (TextOpts s lin2 INSIDE_H KERN False d d)
now you would write:
textSVG' (TextOpts lin2 INSIDE_H KERN False d d) s
.
Reorganisation

LineWidth
andDashing
has moved back toDiagrams.Attributes
.  There is no longer a
Diagrams.Prelude.ThreeD
. Instead all functions are exported byDiagrams.Prelude
and functions have had their types generalised to theR1
,R2
andR3
classes. 
Control.Lens
andData.Default
are now exported fromDiagrams.Prelude
. Some names fromControl.Lens
were hidden.  A new
Diagrams
module now only exports functions defined in the diagrams library. 
Diagrams.TwoD.Transform.ScaleInv
has moved toDiagrams.Transform.ScaleInv
.