Asset System: Prepare File Browser backend for the Asset Browser

The Asset Browser will be a sub-editor of the File Browser. This prepares the
File Browser code for that.

**File-Lists**
* Support loading assets with metadata read from external files into the
  file-list.
* New main based file-list type, for the "Current File" asset library.
* Refresh file-list when switching between browse modes or asset libraries.
* Support empty file-lists (asset library with no assets).
* Store file previews as icons, so scripts can reference them via icon-id. See
  previous commit.

**Space Data**
* Introduce "browse mode" to differeniate between file and asset browsing.
* Add `FileAssetSelectParams` to `SpaceFile`, with `FileSelectParams` as base.
  Makes sure data is separated between asset and file browsing when switching
  between them. The active params can be obtained through
  `ED_fileselect_get_active_params()`.
* `FileAssetSelectParams` stores the currently visible asset library ID.
* Introduce file history abstraction so file and asset browsing can keep a
  separate history (previous and next directories).

**General**
* Option to only show asset data-blocks while file browsing (not exposed here).
* Add "active_file" context member, so scripts can get and display info about
  the active file.
* Add "active_id" context member, so `ED_OT_lib_id_load_custom_preview` can set
  a custom ID preview. (Only for "Current File" asset library)
* Expose some of `FileDirEntry` in RNA as (non-editable). That way scripts can
  obtain name, preview icon and asset-data.

Part of the first Asset Browser milestone. Check the #asset_browser_milestone_1
project milestone on developer.blender.org.

Differential Revision: https://developer.blender.org/D9724

Reviewed by: Bastien Montagne

1 files changed, 15 insertions, 4 deletions

diff --git a/source/blender/editors/space_file/filelist.h b/source/blender/editors/space_file/filelist.h
index 4b8cc052382..59bd5bb50d7 100644
--- a/source/blender/editors/space_file/filelist.h
+++ b/source/blender/editors/space_file/filelist.h
@@ -30,6 +30,7 @@ extern "C" {
 struct BlendHandle;
 struct FileList;
 struct FileSelection;
+struct FileSelectAssetLibraryUID;
 struct wmWindowManager;
 
 struct FileDirEntry;
@@ -46,14 +47,16 @@ typedef enum FileCheckType {
   CHECK_ALL = 3,
 } FileCheckType;
 
-struct ListBase *folderlist_new(void);
 void folderlist_free(struct ListBase *folderlist);
-struct ListBase *folderlist_duplicate(ListBase *folderlist);
 void folderlist_popdir(struct ListBase *folderlist, char *dir);
 void folderlist_pushdir(struct ListBase *folderlist, const char *dir);
 const char *folderlist_peeklastdir(struct ListBase *folderlist);
 int folderlist_clear_next(struct SpaceFile *sfile);
 
+void folder_history_list_ensure_for_active_browse_mode(struct SpaceFile *sfile);
+void folder_history_list_free(struct SpaceFile *sfile);
+struct ListBase folder_history_list_duplicate(struct ListBase *listbase);
+
 void filelist_setsorting(struct FileList *filelist, const short sort, bool invert_sort);
 void filelist_sort(struct FileList *filelist);
 
@@ -63,17 +66,22 @@ void filelist_setfilter_options(struct FileList *filelist,
                                 const bool hide_parent,
                                 const uint64_t filter,
                                 const uint64_t filter_id,
+                                const bool filter_assets_only,
                                 const char *filter_glob,
                                 const char *filter_search);
 void filelist_filter(struct FileList *filelist);
+void filelist_setlibrary(struct FileList *filelist,
+                         const struct FileSelectAssetLibraryUID *asset_library);
 
 void filelist_init_icons(void);
 void filelist_free_icons(void);
 struct ImBuf *filelist_getimage(struct FileList *filelist, const int index);
+struct ImBuf *filelist_file_getimage(const FileDirEntry *file);
 struct ImBuf *filelist_geticon_image(struct FileList *filelist, const int index);
 int filelist_geticon(struct FileList *filelist, const int index, const bool is_main);
 
 struct FileList *filelist_new(short type);
+void filelist_settype(struct FileList *filelist, short type);
 void filelist_clear(struct FileList *filelist);
 void filelist_clear_ex(struct FileList *filelist, const bool do_cache, const bool do_selection);
 void filelist_free(struct FileList *filelist);
@@ -83,15 +91,18 @@ bool filelist_is_dir(struct FileList *filelist, const char *path);
 void filelist_setdir(struct FileList *filelist, char *r_dir);
 
 int filelist_files_ensure(struct FileList *filelist);
-int filelist_empty(struct FileList *filelist);
+int filelist_needs_reading(struct FileList *filelist);
 FileDirEntry *filelist_file(struct FileList *filelist, int index);
 int filelist_file_findpath(struct FileList *filelist, const char *file);
+struct ID *filelist_file_get_id(const struct FileDirEntry *file);
 FileDirEntry *filelist_entry_find_uuid(struct FileList *filelist, const int uuid[4]);
 void filelist_file_cache_slidingwindow_set(struct FileList *filelist, size_t window_size);
 bool filelist_file_cache_block(struct FileList *filelist, const int index);
 
-bool filelist_force_reset(struct FileList *filelist);
+bool filelist_needs_force_reset(struct FileList *filelist);
+void filelist_tag_force_reset(struct FileList *filelist);
 bool filelist_pending(struct FileList *filelist);
+bool filelist_needs_reset_on_main_changes(const struct FileList *filelist);
 bool filelist_is_ready(struct FileList *filelist);
 
 unsigned int filelist_entry_select_set(const struct FileList *filelist,