Fix T91197: marking assets from Python may crash

When using `asset_mark` function from a Python script and afterwards
updating the preview image, a crash might happen. The preview image is
generated by the `asset_mark` function. This may happen on a background
thread, introducing potential synchronization issues.

This patch fixes this by separating the preview generation
`ID.asset_generate_preview` from the mark as asset `ID.asset_mark`.

Note: this separation of "mark as asset" and "generate preview" also
applies to the `ED_asset_mark_id()` C function; if it is desired to have
previews rendered after marking as asset, a call to
`ED_asset_generate_preview()` is now also required.

Reviewed By: sybren

Maniphest Tasks: T91197

Differential Revision: https://developer.blender.org/D12922

3 files changed, 17 insertions, 5 deletions

diff --git a/source/blender/editors/asset/ED_asset_mark_clear.h b/source/blender/editors/asset/ED_asset_mark_clear.h
index d8b8f15a109..bab1d1bf8a5 100644
--- a/source/blender/editors/asset/ED_asset_mark_clear.h
+++ b/source/blender/editors/asset/ED_asset_mark_clear.h
@@ -34,7 +34,14 @@ struct bContext;
  *
  * \return whether the datablock was marked as asset; false when it is not capable of becoming an
  * asset, or when it already was an asset. */
-bool ED_asset_mark_id(const struct bContext *C, struct ID *id);
+bool ED_asset_mark_id(struct ID *id);
+
+/**
+ * Generate preview image for the given datablock.
+ *
+ * The preview image might be generated using a background thread.
+ */
+void ED_asset_generate_preview(const struct bContext *C, struct ID *id);
 
 /**
  * Remove the asset metadata, turning the ID into a "normal" ID.
diff --git a/source/blender/editors/asset/intern/asset_mark_clear.cc b/source/blender/editors/asset/intern/asset_mark_clear.cc
index 8290124c209..e7516bc94c4 100644
--- a/source/blender/editors/asset/intern/asset_mark_clear.cc
+++ b/source/blender/editors/asset/intern/asset_mark_clear.cc
@@ -40,7 +40,7 @@
 #include "ED_asset_list.h"
 #include "ED_asset_mark_clear.h"
 
-bool ED_asset_mark_id(const bContext *C, ID *id)
+bool ED_asset_mark_id(ID *id)
 {
   if (id->asset_data) {
     return false;
@@ -53,14 +53,17 @@ bool ED_asset_mark_id(const bContext *C, ID *id)
 
   id->asset_data = BKE_asset_metadata_create();
 
-  UI_icon_render_id(C, nullptr, id, ICON_SIZE_PREVIEW, true);
-
   /* Important for asset storage to update properly! */
   ED_assetlist_storage_tag_main_data_dirty();
 
   return true;
 }
 
+void ED_asset_generate_preview(const bContext *C, ID *id)
+{
+  UI_icon_render_id(C, nullptr, id, ICON_SIZE_PREVIEW, true);
+}
+
 bool ED_asset_clear_id(ID *id)
 {
   if (!id->asset_data) {
diff --git a/source/blender/editors/asset/intern/asset_ops.cc b/source/blender/editors/asset/intern/asset_ops.cc
index bf532903c7c..33a22775280 100644
--- a/source/blender/editors/asset/intern/asset_ops.cc
+++ b/source/blender/editors/asset/intern/asset_ops.cc
@@ -145,7 +145,9 @@ void AssetMarkHelper::operator()(const bContext &C, PointerRNAVec &ids)
       continue;
     }
 
-    if (ED_asset_mark_id(&C, id)) {
+    if (ED_asset_mark_id(id)) {
+      ED_asset_generate_preview(&C, id);
+
       stats.last_id = id;
       stats.tot_created++;
     }