# Difference between revisions of "Diagrams/Dev/Migrate1.3"

< Diagrams‎ | Dev

This page describes breaking API changes between diagrams 1.2 and 1.3, along with explanations of how to migrate to the new 1.2 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.

## Linear

Diagrams has switched from `vector-space` 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`

`linear`’s functions are very similar to `vector-space`. 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 `vector-space`’s lerp.

The old `HasX`, `HasY` and `HasZ` classes have been replaced by linear’s `R1`, `R2` and `R3`, but these have lenses of the same names (`_x`, `_y`, `_z`) so you probably won't notice the difference.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)`

`angleBetween` is commutative (and always positive).

`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` or `normalised`
• `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 lenses 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 path-like 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.

## diagrams-svg

diagrams-svg no longer depends on the blaze.svg package and instead uses lucid-svg.

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 path-like 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 path-like 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 `diagrams-pgf` 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 `diagrams-html5` 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` and `Dashing` has moved back to `Diagrams.Attributes`.
• There is no longer a `Diagrams.Prelude.ThreeD`. Instead all functions are exported by `Diagrams.Prelude` and functions have had their types generalised to the `R1`, `R2` and `R3` classes.
• `Control.Lens` and `Data.Default` are now exported from `Diagrams.Prelude`. Some names from `Control.Lens` were hidden.
• A new `Diagrams` module now only exports functions defined in the diagrams library.
• `Diagrams.TwoD.Transform.ScaleInv` has moved to `Diagrams.Transform.ScaleInv`.