source/blender/blenloader/intern/versioning_300.cc

@@ -76,6 +76,7 @@
 #include "readfile.h"
 
 #include "SEQ_channels.h"
+#include "SEQ_effects.h"
 #include "SEQ_iterator.h"
 #include "SEQ_retiming.h"
 #include "SEQ_sequencer.h"
@@ -1637,6 +1638,16 @@ static bool version_fix_delete_flag(Sequence *seq, void * /*user_data*/)
   return true;
 }
 
+static bool version_set_seq_single_frame_content(Sequence *seq, void * /*user_data*/)
+{
+  if ((seq->len == 1) &&
+      (seq->type == SEQ_TYPE_IMAGE ||
+       ((seq->type & SEQ_TYPE_EFFECT) && SEQ_effect_get_num_inputs(seq->type) == 0))) {
+    seq->flag |= SEQ_SINGLE_FRAME_CONTENT;
+  }
+  return true;
+}
+
 /* Those `version_liboverride_rnacollections_*` functions mimic the old, pre-3.0 code to find
  * anchor and source items in the given list of modifiers, constraints etc., using only the
  * `subitem_local` data of the override property operation.
@@ -4027,6 +4038,14 @@ void blo_do_versions_300(FileData *fd, Library * /*lib*/, Main *bmain)
       }
     }
 
+    /* Use `SEQ_SINGLE_FRAME_CONTENT` flag instead of weird function to check if strip has multiple
+     * frames. */
+    LISTBASE_FOREACH (Scene *, scene, &bmain->scenes) {
+      Editing *ed = SEQ_editing_get(scene);
+      if (ed != nullptr) {
+        SEQ_for_each_callback(&ed->seqbase, version_set_seq_single_frame_content, nullptr);
+      }
+    }
     /* Keep this block, even when empty. */
   }
 }

source/blender/editors/space_sequencer/sequencer_edit.c

@@ -1851,6 +1851,7 @@ static int sequencer_separate_images_exec(bContext *C, wmOperator *op)
         seq_new->start = start_ofs;
         seq_new->type = SEQ_TYPE_IMAGE;
         seq_new->len = 1;
+        seq->flag |= SEQ_SINGLE_FRAME_CONTENT;
         seq_new->endofs = 1 - step;
 
         /* New strip. */
@@ -2918,6 +2919,13 @@ static int sequencer_change_path_exec(bContext *C, wmOperator *op)
       RNA_END;
     }
 
+    if (len == 1) {
+      seq->flag |= SEQ_SINGLE_FRAME_CONTENT;
+    }
+    else {
+      seq->flag &= ~SEQ_SINGLE_FRAME_CONTENT;
+    }
+
     /* Reset these else we won't see all the images. */
     seq->anim_startofs = seq->anim_endofs = 0;
 

source/blender/makesdna/DNA_sequence_types.h

@@ -580,7 +580,7 @@ enum {
   SEQ_USE_PROXY = (1 << 15),
   SEQ_IGNORE_CHANNEL_LOCK = (1 << 16),
   SEQ_AUTO_PLAYBACK_RATE = (1 << 17),
-  SEQ_FLAG_UNUSED_18 = (1 << 18), /* cleared */
+  SEQ_SINGLE_FRAME_CONTENT = (1 << 18),
   SEQ_FLAG_UNUSED_19 = (1 << 19), /* cleared */
   SEQ_FLAG_UNUSED_21 = (1 << 21), /* cleared */
 

source/blender/sequencer/intern/strip_add.c

@@ -176,6 +176,7 @@ Sequence *SEQ_add_effect_strip(Scene *scene, ListBase *seqbase, struct SeqLoadDa
 
   if (!load_data->effect.seq1) {
     seq->len = 1; /* Effect is generator, set non zero length. */
+    seq->flag |= SEQ_SINGLE_FRAME_CONTENT;
     SEQ_time_right_handle_frame_set(scene, seq, load_data->effect.end_frame);
   }
 
@@ -235,6 +236,10 @@ Sequence *SEQ_add_image_strip(Main *bmain, Scene *scene, ListBase *seqbase, SeqL
   Strip *strip = seq->strip;
   strip->stripdata = MEM_callocN(load_data->image.len * sizeof(StripElem), "stripelem");
 
+  if (seq->len == 1) {
+    seq->flag |= SEQ_SINGLE_FRAME_CONTENT;
+  }
+
   /* Multiview settings. */
   if (load_data->use_multiview) {
     seq->flag |= SEQ_USE_VIEWS;

source/blender/sequencer/intern/strip_time.c

@@ -77,7 +77,7 @@ float seq_give_frame_index(const Scene *scene, Sequence *seq, float timeline_fra
     return -1;
   }
 
-  if (seq->len == 1 && seq->type == SEQ_TYPE_IMAGE) {
+  if (seq->type == SEQ_TYPE_IMAGE && SEQ_transform_single_image_check(seq)) {
     return 0;
   }
 

source/blender/sequencer/intern/strip_transform.c

@@ -36,9 +36,7 @@ static CLG_LogRef LOG = {"seq.strip_transform"};
 
 bool SEQ_transform_single_image_check(Sequence *seq)
 {
-  return ((seq->len == 1) &&
-          (seq->type == SEQ_TYPE_IMAGE ||
-           ((seq->type & SEQ_TYPE_EFFECT) && SEQ_effect_get_num_inputs(seq->type) == 0)));
+  return (seq->flag & SEQ_SINGLE_FRAME_CONTENT) != 0;
 }
 
 bool SEQ_transform_seqbase_isolated_sel_check(ListBase *seqbase)