1By using custom importers, Sass stylesheets can be implemented in any possible way, such as by being loaded via a remote server. Please note: this feature is experimental and is implemented differently than importers in Ruby Sass. Imports must be relative to the parent import context and therefore we need to pass this information to the importer callback. This is currently done by passing the complete import string/path of the previous import context.
2
3## Return Imports
4
5You actually have to return a list of imports, since some importers may want to import multiple files from one import statement (ie. a glob/star importer).  The memory you pass with source and srcmap is taken over by LibSass and freed automatically when the import is done. You are also allowed to return `0` instead of a list, which will tell LibSass to handle the import by itself (as if no custom importer was in use).
6
7```C
8Sass_Import_Entry* rv = sass_make_import_list(1);
9rv[0] = sass_make_import(rel, abs, source, srcmap);
10```
11
12Every import will then be included in LibSass. You are allowed to only return a file path without any loaded source. This way you can ie. implement rewrite rules for import paths and leave the loading part for LibSass.
13
14Please note that LibSass doesn't use the srcmap parameter yet. It has been added to not deprecate the C-API once support has been implemented. It will be used to re-map the actual sourcemap with the provided ones.
15
16### Basic Usage
17
18```C
19#include "sass/functions.h"
20```
21
22## Sass Importer API
23
24```C
25// Forward declaration
26struct Sass_Import;
27
28// Forward declaration
29struct Sass_C_Import_Descriptor;
30
31// Typedef defining the custom importer callback
32typedef struct Sass_C_Import_Descriptor (*Sass_C_Import_Callback);
33// Typedef defining the importer c function prototype
34typedef Sass_Import_Entry* (*Sass_C_Import_Fn) (const char* url, const char* prev, void* cookie);
35
36// Creators for custom importer callback (with some additional pointer)
37// The pointer is mostly used to store the callback into the actual function
38Sass_C_Import_Callback sass_make_importer (Sass_C_Import_Fn, void* cookie);
39
40// Getters for import function descriptors
41Sass_C_Import_Fn sass_import_get_function (Sass_C_Import_Callback fn);
42void* sass_import_get_cookie (Sass_C_Import_Callback fn);
43
44// Deallocator for associated memory
45void sass_delete_importer (Sass_C_Import_Callback fn);
46
47// Creator for sass custom importer return argument list
48Sass_Import_Entry* sass_make_import_list (size_t length);
49// Creator for a single import entry returned by the custom importer inside the list
50Sass_Import_Entry sass_make_import_entry (const char* path, char* source, char* srcmap);
51Sass_Import_Entry sass_make_import (const char* rel, const char* abs, char* source, char* srcmap);
52
53// set error message to abort import and to print out a message (path from existing object is used in output)
54Sass_Import_Entry sass_import_set_error(Sass_Import_Entry import, const char* message, size_t line, size_t col);
55
56// Setters to insert an entry into the import list (you may also use [] access directly)
57// Since we are dealing with pointers they should have a guaranteed and fixed size
58void sass_import_set_list_entry (Sass_Import_Entry* list, size_t idx, Sass_Import_Entry entry);
59Sass_Import_Entry sass_import_get_list_entry (Sass_Import_Entry* list, size_t idx);
60
61// Getters for import entry
62const char* sass_import_get_imp_path (Sass_Import_Entry);
63const char* sass_import_get_abs_path (Sass_Import_Entry);
64const char* sass_import_get_source (Sass_Import_Entry);
65const char* sass_import_get_srcmap (Sass_Import_Entry);
66// Explicit functions to take ownership of these items
67// The property on our struct will be reset to NULL
68char* sass_import_take_source (Sass_Import_Entry);
69char* sass_import_take_srcmap (Sass_Import_Entry);
70
71// Getters for import error entries
72size_t sass_import_get_error_line (Sass_Import_Entry);
73size_t sass_import_get_error_column (Sass_Import_Entry);
74const char* sass_import_get_error_message (Sass_Import_Entry);
75
76// Deallocator for associated memory (incl. entries)
77void sass_delete_import_list (Sass_Import_Entry*);
78// Just in case we have some stray import structs
79void sass_delete_import (Sass_Import_Entry);
80```
81
82### More links
83
84- [Sass Importer Example](api-importer-example.md)
85- [Sass Importer Internal](api-importer-internal.md)
86
87