+Sfinv API
+---------
+
+It is recommended that you read this link for a good introduction to the
+sfinv API by its author: https://rubenwardy.com/minetest_modding_book/en/chapters/sfinv.html
+
+### sfinv Methods
+
+**Pages**
+
+* sfinv.set_page(player, pagename) - changes the page
+* sfinv.get_page(player) - get the current page name. Will never return nil
+* sfinv.get_homepage_name(player) - get the page name of the first page to show to a player
+* sfinv.register_page(name, def) - register a page, see section below
+* sfinv.override_page(name, def) - overrides fields of an page registered with register_page.
+ * Note: Page must already be defined, (opt)depend on the mod defining it.
+* sfinv.set_player_inventory_formspec(player) - (re)builds page formspec
+ and calls set_inventory_formspec().
+* sfinv.get_formspec(player, context) - builds current page's formspec
+
+**Contexts**
+
+* sfinv.get_or_create_context(player) - gets the player's context
+* sfinv.set_context(player, context)
+
+**Theming**
+
+* sfinv.make_formspec(player, context, content, show_inv, size) - adds a theme to a formspec
+ * show_inv, defaults to false. Whether to show the player's main inventory
+ * size, defaults to `size[8,8.6]` if not specified
+* sfinv.get_nav_fs(player, context, nav, current_idx) - creates tabheader or ""
+
+### sfinv Members
+
+* pages - table of pages[pagename] = def
+* pages_unordered - array table of pages in order of addition (used to build navigation tabs).
+* contexts - contexts[playername] = player_context
+* enabled - set to false to disable. Good for inventory rehaul mods like unified inventory
+
+### Context
+
+A table with these keys:
+
+* page - current page name
+* nav - a list of page names
+* nav_titles - a list of page titles
+* nav_idx - current nav index (in nav and nav_titles)
+* any thing you want to store
+ * sfinv will clear the stored data on log out / log in
+
+### sfinv.register_page
+
+sfinv.register_page(name, def)
+
+def is a table containing:
+
+* `title` - human readable page name (required)
+* `get(self, player, context)` - returns a formspec string. See formspec variables. (required)
+* `is_in_nav(self, player, context)` - return true to show in the navigation (the tab header, by default)
+* `on_player_receive_fields(self, player, context, fields)` - on formspec submit.
+* `on_enter(self, player, context)` - called when the player changes pages, usually using the tabs.
+* `on_leave(self, player, context)` - when leaving this page to go to another, called before other's on_enter
+
+### get formspec
+
+Use sfinv.make_formspec to apply a layout:
+
+ return sfinv.make_formspec(player, context, [[
+ list[current_player;craft;1.75,0.5;3,3;]
+ list[current_player;craftpreview;5.75,1.5;1,1;]
+ image[4.75,1.5;1,1;gui_furnace_arrow_bg.png^[transformR270]
+ listring[current_player;main]
+ listring[current_player;craft]
+ image[0,4.25;1,1;gui_hb_bg.png]
+ image[1,4.25;1,1;gui_hb_bg.png]
+ image[2,4.25;1,1;gui_hb_bg.png]
+ image[3,4.25;1,1;gui_hb_bg.png]
+ image[4,4.25;1,1;gui_hb_bg.png]
+ image[5,4.25;1,1;gui_hb_bg.png]
+ image[6,4.25;1,1;gui_hb_bg.png]
+ image[7,4.25;1,1;gui_hb_bg.png]
+ ]], true)
+
+See above (methods section) for more options.
+
+### Customising themes
+
+Simply override this function to change the navigation:
+
+ function sfinv.get_nav_fs(player, context, nav, current_idx)
+ return "navformspec"
+ end
+
+And override this function to change the layout:
+
+ function sfinv.make_formspec(player, context, content, show_inv, size)
+ local tmp = {
+ size or "size[8,8.6]",
+ theme_main,
+ sfinv.get_nav_fs(player, context, context.nav_titles, context.nav_idx),
+ content
+ }
+ if show_inv then
+ tmp[4] = theme_inv
+ end
+ return table.concat(tmp, "")
+ end
+
+