Module Bogue.Long_list

module Long_list: sig .. end

Handle large lists by not displaying all elements at once.

Very quickly, displaying a list of layouts (for instance, listing files in a directory) can run the computer out of memory if it tries to keep in memory the textures of all entries of the list. In these cases you need to use a Long_list.

See for instance Example #34 that displays a list of 1 million entries.

Long_lists may contain any type of Layout. They don't need to be all of the same dimension. Instead of providing the list of layouts, one must give a function generate such that the layout given by generate i is the i-eth element of the list.

Dependency graph

type t

val create : ?name:string ->
       w:int ->
       h:int ->
       length:int ->
       ?first:int ->
       generate:(int -> Layout.t) ->
       ?height_fn:(int -> int option) ->
       ?cleanup:(Layout.t -> unit) ->
       ?max_memory:int ->
       ?linear:bool ->
       ?scrollbar_width:int -> ?scale_width:bool -> unit -> t

Create a long list through the function generate which maps any index i to the ieth element (layout) of the list. If specified (which is not a good idea), the max_memory should be at least twice the area (in physical pixels) of the visible part of the list. If the number of elements is large (typically 100000 or more, this depends on your CPU), its is highly advisable to provide a height_fn, which to an index i gives the height (in logical pixels) of the ieth entry. If some heights are not known in advance, it's ok to return None. For instance, if all entries have the same height, say 30 pixels, one can define

 let height_fn _ = Some 30

val create_layout : ?name:string ->
       w:int ->
       h:int ->
       length:int ->
       ?first:int ->
       generate:(int -> Layout.t) ->
       ?height_fn:(int -> int option) ->
       ?cleanup:(Layout.t -> unit) ->
       ?max_memory:int ->
       ?linear:bool ->
       ?scrollbar_width:int -> ?scale_width:bool -> unit -> Layout.t

Similar to create but only returns the layout. Equivalent to calling Long_list.get_layout to the result of create.

val get_layout : t -> Layout.t

val get_scroll : t -> float

Return the scroll percentage of the Long list, between 0 and 1. A value of 0 means no scroll: the first row is visible. The value 1 means that the scrollbar is fully downwards, the last row is visible.

val set_scroll : t -> float -> unit