Final 'FileBrowser First Stage' merge.

It basically rewrites most of filelist.c, with some more limited changes in other areas of filebrowser.

From user perspective, it:
* Removes some info in 'long' drawing mode (owner, permissions) - OS-specific data that do not really matter in Blender!
* Makes short/long display 'fixed' size (among four choices, like thumbnails mode).
* Allows to list several layers of dirtree at once, in a flat way (inside .blend files and/or real directories).
* Consequently, adds datablocks types filtering.
* Uses way less RAM when listing big directories, especially in thumbnail mode (we are talking of several hundred of MiB spared).
* Generates thumbnails way faster.

From code perspective, it:
* Is ready for asset engine needs (on data structure level in filebrowser's listing).
* Simplifies and makes 'generic' file listing much lighter.
* Separates file listing in three different aspects:
** 'generic' filelisting (in BLI), which becomes a shallow wrapper around stat struct.
** 'filebrowser drawing' filelisting, which only contains current visible subset of the whole list (sliding window), with extra drawing data (strings for size, date/time, preview, etc.).
** 'asset-ready' filelisting, which is used for operations common to 'basic' filehandling and future asset-related one.
* Uses uuid's to handle file selection/state in the browser, instead of using flags in filelisting items.
* Uses much lighter BLI_task handling for previews, instead of heavy 'job' system (using the new 'notifier' timer to handle UI refresh, in similar way to jobs).
* Moves .blend datablocks preview handling to IMB_thumbnail (necessary to avoid storing all datablock previews at once, and gives better consistency and performances too).

Revision: https://developer.blender.org/D1316

Thanks to Campbell & Sergey for the reviews. :)

release/scripts/startup/bl_ui/space_filebrowser.py

@@ -40,22 +40,23 @@ class FILEBROWSER_HT_header(Header):
         row.operator("file.parent", text="", icon='FILE_PARENT')
         row.operator("file.refresh", text="", icon='FILE_REFRESH')
 
-        row = layout.row()
-        row.separator()
-
-        row = layout.row(align=True)
+        layout.separator()
         layout.operator_context = 'EXEC_DEFAULT'
-        row.operator("file.directory_new", icon='NEWFOLDER')
+        layout.operator("file.directory_new", icon='NEWFOLDER', text="")
+        layout.separator()
 
         layout.operator_context = 'INVOKE_DEFAULT'
         params = st.params
 
         # can be None when save/reload with a file selector open
         if params:
+            is_lib_browser = params.use_library_browsing
+
+            layout.prop(params, "recursion_level", text="")
+
             layout.prop(params, "display_type", expand=True, text="")
 
-            if params.display_type == 'FILE_IMGDISPLAY':
-                layout.prop(params, "thumbnail_size", text="")
+            layout.prop(params, "thumbnail_size", text="")
 
             layout.prop(params, "sort_method", expand=True, text="")
 
@@ -81,9 +82,17 @@ class FILEBROWSER_HT_header(Header):
                 row.prop(params, "use_filter_sound", text="")
                 row.prop(params, "use_filter_text", text="")
 
+            if is_lib_browser:
+                row.prop(params, "use_filter_blendid", text="")
+                if params.use_filter_blendid:
+                    row.separator()
+                    row.prop(params, "filter_id_category", text="")
+
             row.separator()
             row.prop(params, "filter_search", text="", icon='VIEWZOOM')
 
+        layout.template_running_jobs()
+
 
 class FILEBROWSER_UL_dir(bpy.types.UIList):
     def draw_item(self, context, layout, data, item, icon, active_data, active_propname, index):
@@ -214,5 +223,24 @@ class FILEBROWSER_PT_recent_folders(Panel):
             col.operator("file.reset_recent", icon='X', text="")
 
 
+class FILEBROWSER_PT_advanced_filter(Panel):
+    bl_space_type = 'FILE_BROWSER'
+    bl_region_type = 'TOOLS'
+    bl_category = "Filter"
+    bl_label = "Advanced Filter"
+
+    def draw(self, context):
+        layout = self.layout
+        space = context.space_data
+        params = space.params
+
+        if params and params.use_library_browsing:
+            layout.prop(params, "use_filter_blendid")
+            if params.use_filter_blendid:
+                layout.separator()
+                col = layout.column()
+                col.prop(params, "filter_id")
+
+
 if __name__ == "__main__":  # only for live edit.
     bpy.utils.register_module(__name__)