Images: refactor how failed image load attempts are remembered

Previously, `ImageTile->ok` and `ImageUser->ok` were used to indicate
whether an image failed to load. There were three possible values
which (probably) had the following meanings:
* `0`: There was an error while loading the image. Don't try to load again.
* `1`: Default value. Try to load the image.
* `2`: The image was loaded successfully.

This image-wide flag did not make sense unfortunately, because loading
may work for some frames of an image sequence but not for others.
Remember than an image data block can also contain a movie.

The purpose of the `->ok` flag was to serve as an optimization to avoid
trying to load a file over and over again when there is an error (e.g. the
file does not exist or is invalid). To get the optimization back, the patch
is changing `MovieCache` so that it can also cache failed load attempts.
As a consequence, `ibuf` is allowed to be `NULL` in a few more places.
I added the appropriate null checks.

This also solves issues when image sequences are used with the
Image Texture node in Geometry nodes (also see D12827).

Differential Revision: https://developer.blender.org/D12957

3 files changed, 2 insertions, 7 deletions

diff --git a/source/blender/editors/space_image/image_buttons.c b/source/blender/editors/space_image/image_buttons.c
index 86349a64681..5b83f681d17 100644
--- a/source/blender/editors/space_image/image_buttons.c
+++ b/source/blender/editors/space_image/image_buttons.c
@@ -729,10 +729,6 @@ static void rna_update_cb(bContext *C, void *arg_cb, void *UNUSED(arg))
 {
   RNAUpdateCb *cb = (RNAUpdateCb *)arg_cb;
 
-  /* ideally this would be done by RNA itself, but there we have
-   * no image user available, so we just update this flag here */
-  cb->iuser->ok = 1;
-
   /* we call update here on the pointer property, this way the
    * owner of the image pointer can still define its own update
    * and notifier */
diff --git a/source/blender/editors/space_image/image_ops.c b/source/blender/editors/space_image/image_ops.c
index ae56238d73f..478e484924a 100644
--- a/source/blender/editors/space_image/image_ops.c
+++ b/source/blender/editors/space_image/image_ops.c
@@ -2227,7 +2227,7 @@ static int image_save_sequence_exec(bContext *C, wmOperator *op)
     iter = IMB_moviecacheIter_new(image->cache);
     while (!IMB_moviecacheIter_done(iter)) {
       ibuf = IMB_moviecacheIter_getImBuf(iter);
-      if (ibuf->userflags & IB_BITMAPDIRTY) {
+      if (ibuf != NULL && ibuf->userflags & IB_BITMAPDIRTY) {
         if (first_ibuf == NULL) {
           first_ibuf = ibuf;
         }
@@ -2251,7 +2251,7 @@ static int image_save_sequence_exec(bContext *C, wmOperator *op)
   while (!IMB_moviecacheIter_done(iter)) {
     ibuf = IMB_moviecacheIter_getImBuf(iter);
 
-    if (ibuf->userflags & IB_BITMAPDIRTY) {
+    if (ibuf != NULL && ibuf->userflags & IB_BITMAPDIRTY) {
       char name[FILE_MAX];
       BLI_strncpy(name, ibuf->name, sizeof(name));
 
diff --git a/source/blender/editors/space_image/image_undo.c b/source/blender/editors/space_image/image_undo.c
index cc6effd0f71..3fbcc8348c8 100644
--- a/source/blender/editors/space_image/image_undo.c
+++ b/source/blender/editors/space_image/image_undo.c
@@ -668,7 +668,6 @@ static UndoImageHandle *uhandle_add(ListBase *undo_handles, Image *image, ImageU
   uh->image_ref.ptr = image;
   uh->iuser = *iuser;
   uh->iuser.scene = NULL;
-  uh->iuser.ok = 1;
   BLI_addtail(undo_handles, uh);
   return uh;
 }