package archimedes

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Module Archimedes.Coordinate

Systems of coordinates (inhomogeneous homotheties) relative to other coordinate systems with automatic updates. The automatic update refers to the fact that, if a coordinate system is upated, all coordinate systems which depend on it (possibly through several intermediate coordinate systems), they will use the updated version.

type t

Mutable affine coordinate system.

type ctm

Current transformation matrix of the backend (to be able to restore it with Coordinate.restore.

val use : Backend.t -> t -> ctm

After a call to use b c, all backend operations will be performed in the coordinates c. It returns the current coordinate system so one can restore it with Coordinate.restore.

val restore : Backend.t -> ctm -> unit

restore b c restore the coordinate transformation matrix ctm for the backend b.

Transforming coordinates

val to_parent : t -> x:float -> y:float -> float * float

to_parent coord x y returns the location of the point (x,y) in parent's coordinates.

val from_parent : t -> x:float -> y:float -> float * float

from_child coord x y returns the location of the point (x,y) from parent's coordinates.

val to_device : t -> x:float -> y:float -> float * float

to_device coord x y returns the location of the point (x,y) in device coordinates.

val to_device_distance : t -> dx:float -> dy:float -> float * float

to_device coord dx dy returns the distance (dx,dy) in device coordinates (i.e. the translation in coord is ignored).

val to_coord : t -> x:float -> y:float -> float * float

to_coord coord x y converts the (device) point (x,y) into the corresponding point, expressed in coord coordinates.

val to_coord_distance : t -> dx:float -> dy:float -> float * float

to_coord coord x y converts the (device) distance (dx,dy) into the corresponding distance, expressed in coord coordinates.

Creating new coordinate systems

val make_root : Matrix.Homothety.t -> t

make_root m make a system of coordinates which, when used, amounts to use m. This coordinate system depends on no other so will never be updated. It can be modified however (the matrix m is copied so no modification will affect m).

val make_identity : t -> t

make_identity coord defines a new system of coordinates that initially consist in the identity transformation to coord.

val make_translate : t -> x:float -> y:float -> t

make_translate coord x y defines a new coordinate system that consists in moving the origin of coord to the point (x,y) (understood as coordinates in the system coord). If coord is modified, the new system will be updated as well.

val make_scale : t -> x:float -> y:float -> t

make_scale coord x y defines a new coordinate system that consists in dilating axis X and Y of coord by a factor of x and y respectively. If coord is modified, the new system will be updated as well.

val make_from_transform : t -> Matrix.Homothety.t -> t

make_from_transform coord tm defines a new coordinate system that consists first in applying tm and then the tranformation in coord. In other words, tm is the transformation from the desired coordinate system to coord. If coord is modified, the new system will be updated as well.

val copy : t -> t

Returns a completely independent copy of the current coordinate system.

Modifying this coordinate system

val translate : t -> x:float -> y:float -> unit

translate coord x y modifies the coordinate system coord translating its origin to the point (x,y) (understood as coordinates in the system coord).

val scale : t -> x:float -> y:float -> unit

scale coord x y modifies the coordinate system coord dilating its axis X and Y by a factor of x and y respectively.

val transform : t -> Matrix.t -> unit

transform coord tm modifies the coordinate system coord changing the transformation matrix to its parent (the one it was created from) to tm.

Monitoring coordinate systems for updates

type monitor

Handle to monitor the updates to a coordinate system.

val monitor : t -> monitor

monitor coord creates a new monitor for changes to coord (initially not set).

val reset : monitor -> unit

reset m reset the monitor. See Coordinate.changed.

val changed : monitor -> bool

changed m tell whether the coordinate system m is attached to was updated (possibly because of one of the coordinate systems it (transitively) depends on was mofidied) since the last reset.