Module type Archimedes.Backend.T

module type T = sig .. end
The interface that backends must provide to be registered.

type t 
Handle to a backend.
val set_color : t -> Archimedes.Color.t -> unit
set_color bk c sets the color of the backend bk to c.
val set_line_width : t -> float -> unit
set_line_width bk w sets the line width of the backend bk to w. The line width is expressed in the natural backend coordinates (i.e. when the CTM is the identity).
val set_line_cap : t -> Archimedes.Backend.line_cap -> unit
set_line_cap bk c sets the line cap for the backend bk to c.
val set_dash : t -> float -> float array -> unit
set_dash bk ofs pattern
val set_line_join : t -> Archimedes.Backend.line_join -> unit
set_line_join bk j sets the line join for the backend bk to j.
val get_line_width : t -> float
val get_line_cap : t -> Archimedes.Backend.line_cap
val get_dash : t -> float array * float
val get_line_join : t -> Archimedes.Backend.line_join
val move_to : t -> x:float -> y:float -> unit
Begin a new sub-path. After this call the current point will be (x, y).
val line_to : t -> x:float -> y:float -> unit
line_to bk x y Adds a line to the path from the current point to position (x, y) in the current backend coordinates. After this call the current point will be (x, y).

If there is no current point before the call to line_to this function will behave as Archimedes.Backend.T.move_to bk x y.

val rel_move_to : t -> x:float -> y:float -> unit
val rel_line_to : t -> x:float -> y:float -> unit
val curve_to : t ->
x1:float -> y1:float -> x2:float -> y2:float -> x3:float -> y3:float -> unit
curve_to bk x1 y1 x2 y2 x3 y3 adds an Bezier curve to the path, starting at the current point, ending at point (x3,y3), with control points (x1,y1) and (x2,y2).
val rectangle : t -> x:float -> y:float -> w:float -> h:float -> unit
rectangle bk x y w h adds to the current path of bk a rectangle whose lower left corner is at (x,y) and width and height are respectively w and h.
val arc : t -> r:float -> a1:float -> a2:float -> unit
arc bk r a1 a2 add an arc to the current path starting from the current point with a radius r, starting at angle a1 and going clockwise to angle a2.
val close_path : t -> unit
Adds a line segment to the path from the current point to the beginning of the current sub-path (the most recent point passed to Archimedes.Backend.T.move_to) and closes this sub-path.
val clear_path : t -> unit
Clears the current path. After this call there will be no path. Nothing is guaranteed about the current point (it may not be preserved).
val path_extents : t -> Archimedes.Matrix.rectangle
val stroke : t -> unit
stroke bk draw the curve described by the current path according to the current line width and color.
val stroke_preserve : t -> unit
Same as Archimedes.Backend.T.stroke but make sure the current path is unmodified.
val fill : t -> unit
fill bk draw the curve described by the current path according to the current line width and color. The current path may be modified. This is affected by the CTM.
val fill_preserve : t -> unit
Same as Archimedes.Backend.T.fill but make sure the current path is unmodified.
val stroke_path_preserve : t -> Archimedes.Path.t -> unit
stroke_path bk p stroke the abstract path p, where its coordinates are interpreted in the current transformation matrix. Of course, the current clipping, line width and color are be obeyed. This function may modify the current path in bk.

For backend developers: the internal representation of the path is available in Archimedes_internals.Path.

val fill_path_preserve : t -> Archimedes.Path.t -> unit
fill_path_preserve is similar to stroke_path_preserve except that it fills the path.
val fill_with_color : t -> Archimedes.Color.t -> unit
fill_with_color t c fill the current path of t with the color c. Even if the color is transparent, it must replace all underlying elements (contrarily to Archimedes.Backend.T.fill which will show the underlying elements through a transparent color). If transparency is not supported by the backend, it does the same as Archimedes.Backend.T.fill, except that this operation does not change the current color of the backend. It may modify the current path however.
val show : t -> unit
Some backends may not show immediately the action of Archimedes.Backend.T.stroke, Archimedes.Backend.T.fill, Archimedes.Backend.T.stroke_path_preserve,... immediately (usually because it is expensive but also to avoid flicker during animations). show bk forces the backend to update.
val clip_rectangle : t -> x:float -> y:float -> w:float -> h:float -> unit
Establishes a new clip rectangle by intersecting the current clip rectangle. This may clear the current path. Calling can only make the clip region smaller, never larger. For clip_rectangle to have only a local effect, put it in a / Archimedes.Backend.T.restore group.

clip_rectangle is garantee to respect the CTM only if the components xy and yx of the matrix are both 0..

val save : t -> unit
Save the current state of the backend. Note that save/restore must not affect the current path.
val restore : t -> unit
Restore the saved state of the backend.
val translate : t -> x:float -> y:float -> unit
translate cr tx ty modifies the current transformation matrix by translating the user-space origin by (tx,ty).
val scale : t -> x:float -> y:float -> unit
scale sx sy modifies the current transformation matrix by scaling the X and Y user-space axes by sx and sy respectively.
val rotate : t -> angle:float -> unit
Modifies the current transformation matrix by rotating the user-space axes by angle radians.
val set_matrix : t -> Archimedes.Matrix.t -> unit
Set the current transformation matrix which is the matrix transorming user to device coordinates.
val get_matrix : t -> Archimedes.Matrix.t
Return the current transformation matrix. Modifying this matrix does not affect the matrix held in t.
val flipy : t -> bool
true iff this kind of device has its Y axis pointing downwards. FIXME: really needed ? Beware that on some devices, the font display happens in the current coordinates.
val select_font_face : t ->
Archimedes.Backend.slant -> Archimedes.Backend.weight -> string -> unit
select_font_face t slant weight family selects a family and style of font from a simplified description as a family name, slant and weight. Family names are bakend dependent. Raise an exception if the face is not supported.
val set_font_size : t -> float -> unit
Set the scaling of the font.
val text_extents : t -> string -> Archimedes.Matrix.rectangle
Returns a rectangle whose width and height specify respectively the length and the height of the text. The x and y values give the lower bottom point of the rectangle as if the text was placed at the origin.
val show_text : t ->
rotate:float ->
x:float -> y:float -> Archimedes.Backend.text_position -> string -> unit
show_text t angle x y pos txt displays txt at the point (x,y) as indicated by pos. The point (x,y) is in the current coordinate system but the current transformation matrix will NOT be applied to the text itself. angle indicates by how many radians the text must be rotated w.r.t. the x-axis (in the current coordinate system, assuming it is orthonormal) -- not all device support rotations of angles <> 0. (in device coordinates). This is an immediate operation: no stroke nor fill are required (nor will have any effect).