Fix T87621: Win32 Do Not Create Preview Thumbnails for Offline Files

This patch turns off the creation of file thumbnails for files that are
offline and therefore not fully-present on the file system. These types
of files - typically cloud-based or stored on slower backup media -
only have their contents available when actually accessed, at which
point there will be a short delay. If we allow thumbnail creation in
this state then all offline files in a folder will be downloaded just
to view a listing, which can take a long time.

Files in this state will instead get a more generic thumbnail that
still indicates file type (icon in center) and that shows offline state
will a special icon at the bottom-left.

Although this currently only affects Windows users, most of this patch
is platform-agnostic. So other platforms inherit this behavior if they
only add FILE_ATTR_OFFLINE attribute to files in this state.

See D11101 for more information.

Differential Revision: https://developer.blender.org/D11101

Reviewed by Julian Eisel

2 files changed, 3 insertions, 2 deletions

diff --git a/source/blender/blenlib/BLI_fileops.h b/source/blender/blenlib/BLI_fileops.h
index df80e720363..bf18dd1070e 100644
--- a/source/blender/blenlib/BLI_fileops.h
+++ b/source/blender/blenlib/BLI_fileops.h
@@ -87,7 +87,7 @@ typedef enum eFileAttributes {
   FILE_ATTR_RESTRICTED = 1 << 6,      /* Protected by OS. */
   FILE_ATTR_TEMPORARY = 1 << 7,       /* Used for temporary storage. */
   FILE_ATTR_SPARSE_FILE = 1 << 8,     /* Sparse File. */
-  FILE_ATTR_OFFLINE = 1 << 9,         /* Data is not immediately available. */
+  FILE_ATTR_OFFLINE = 1 << 9,         /* Contents available after a short delay. */
   FILE_ATTR_ALIAS = 1 << 10,          /* Mac Alias or Windows LNK. File-based redirection. */
   FILE_ATTR_REPARSE_POINT = 1 << 11,  /* File has associated re-parse point. */
   FILE_ATTR_SYMLINK = 1 << 12,        /* Reference to another file. */
diff --git a/source/blender/blenlib/intern/storage.c b/source/blender/blenlib/intern/storage.c
index cb2634e6fda..5f823396ed9 100644
--- a/source/blender/blenlib/intern/storage.c
+++ b/source/blender/blenlib/intern/storage.c
@@ -266,7 +266,8 @@ eFileAttributes BLI_file_attributes(const char *path)
   if (attr & FILE_ATTRIBUTE_SPARSE_FILE) {
     ret |= FILE_ATTR_SPARSE_FILE;
   }
-  if (attr & FILE_ATTRIBUTE_OFFLINE) {
+  if (attr & FILE_ATTRIBUTE_OFFLINE || attr & FILE_ATTRIBUTE_RECALL_ON_OPEN ||
+      attr & FILE_ATTRIBUTE_RECALL_ON_DATA_ACCESS) {
     ret |= FILE_ATTR_OFFLINE;
   }
   if (attr & FILE_ATTRIBUTE_REPARSE_POINT) {