Fix file/asset thumbnails causing constant stream of notifiers

The thumbnail caching continuously sends `ND_SPACE_FILE_PREVIEW`
notifiers via a timer. But this timer was never ended properly after
thumbnails are fully loaded into the cache.
Wouldn't actually cause a refresh or redraw, send and process the
notifiers.

I already tried to avoid this for the asset view template, but
apparently that wasn't working correctly. For the File/Asset Browser I
never applied that fix to avoid possible regressions before the release.

2 files changed, 10 insertions, 5 deletions

diff --git a/source/blender/editors/space_file/file_draw.c b/source/blender/editors/space_file/file_draw.c
index 9f18f6d1443..14c786e5dea 100644
--- a/source/blender/editors/space_file/file_draw.c
+++ b/source/blender/editors/space_file/file_draw.c
@@ -906,7 +906,8 @@ void file_draw_list(const bContext *C, ARegion *region)
      * since it's filelist_file_cache_block() and filelist_cache_previews_update()
      * which controls previews task. */
     {
-      const bool previews_running = filelist_cache_previews_running(files);
+      const bool previews_running = filelist_cache_previews_running(files) &&
+                                    !filelist_cache_previews_done(files);
       //          printf("%s: preview task: %d\n", __func__, previews_running);
       if (previews_running && !sfile->previews_timer) {
         sfile->previews_timer = WM_event_add_timer_notifier(
diff --git a/source/blender/editors/space_file/filelist.c b/source/blender/editors/space_file/filelist.c
index b5eb7905fd8..2d31e8030a4 100644
--- a/source/blender/editors/space_file/filelist.c
+++ b/source/blender/editors/space_file/filelist.c
@@ -339,7 +339,10 @@ typedef struct FileListEntryCache {
   /* Previews handling. */
   TaskPool *previews_pool;
   ThreadQueue *previews_done;
-  size_t previews_todo_count;
+  /** Counter for previews that are not fully loaded and ready to display yet. So includes all
+   * previews either in `previews_pool` or `previews_done`. #filelist_cache_previews_update() makes
+   * previews in `preview_done` ready for display, so the counter is decremented there. */
+  int previews_todo_count;
 } FileListEntryCache;
 
 /* FileListCache.flags */
@@ -1647,7 +1650,6 @@ static void filelist_cache_preview_runf(TaskPool *__restrict pool, void *taskdat
   preview_taskdata->preview = NULL;
 
   BLI_thread_queue_push(cache->previews_done, preview);
-  atomic_fetch_and_sub_z(&cache->previews_todo_count, 1);
 
   //  printf("%s: End (%d)...\n", __func__, threadid);
 }
@@ -1689,6 +1691,7 @@ static void filelist_cache_previews_clear(FileListEntryCache *cache)
       }
       MEM_freeN(preview);
     }
+    cache->previews_todo_count = 0;
   }
 }
 
@@ -1759,7 +1762,6 @@ static void filelist_cache_previews_push(FileList *filelist, FileDirEntry *entry
       preview->icon_id = BKE_icon_imbuf_create(imbuf);
     }
     BLI_thread_queue_push(cache->previews_done, preview);
-    atomic_fetch_and_sub_z(&cache->previews_todo_count, 1);
   }
   else {
     if (entry->redirection_path) {
@@ -1780,6 +1782,7 @@ static void filelist_cache_previews_push(FileList *filelist, FileDirEntry *entry
                        true,
                        filelist_cache_preview_freef);
   }
+  cache->previews_todo_count++;
 }
 
 static void filelist_cache_init(FileListEntryCache *cache, size_t cache_size)
@@ -2693,6 +2696,7 @@ bool filelist_cache_previews_update(FileList *filelist)
     }
 
     MEM_freeN(preview);
+    cache->previews_todo_count--;
   }
 
   return changed;
@@ -2714,7 +2718,7 @@ bool filelist_cache_previews_done(FileList *filelist)
   }
 
   return (cache->previews_pool == NULL) || (cache->previews_done == NULL) ||
-         (cache->previews_todo_count == (size_t)BLI_thread_queue_len(cache->previews_done));
+         (cache->previews_todo_count == 0);
 }
 
 /* would recognize .blend as well */