From 56640440f0742427e5f989cbcf98f7d48ddd275f Mon Sep 17 00:00:00 2001
From: Julian Eisel <julian@blender.org>
Date: Wed, 5 Apr 2023 16:50:10 +0200
Subject: [PATCH] Fix crash loading pre 2.5 test file (Cycles test failure)

fa0f295b53 exposed that there was a region missing because of some
faulty versioning.

The `fluid_motion_blur.blend` Cycles test file was crashing. Seems like
this is a pre 2.5 file that was resaved in newer versions, but the
preview region for the Sequencer was missing. Before mentioned commit,
the region would be broken when activating the preview view mode in the
Sequencer, now it would crash even on startup.

Ensure the region exists, as expected.
---
 source/blender/blenloader/intern/versioning_250.c    |  4 +++-
 source/blender/blenloader/intern/versioning_300.cc   | 10 ++++++++++
 source/blender/blenloader/intern/versioning_common.h |  2 ++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/source/blender/blenloader/intern/versioning_250.c b/source/blender/blenloader/intern/versioning_250.c
index c4a3690aea9..a4bd14d1495 100644
--- a/source/blender/blenloader/intern/versioning_250.c
+++ b/source/blender/blenloader/intern/versioning_250.c
@@ -72,6 +72,8 @@
 
 #include "readfile.h"
 
+#include "versioning_common.h"
+
 #include <errno.h>
 
 /* Make preferences read-only, use versioning_userdef.c. */
@@ -100,7 +102,7 @@ static void area_add_header_region(ScrArea *area, ListBase *lb)
   region->v2d.flag = (V2D_PIXELOFS_X | V2D_PIXELOFS_Y);
 }
 
-static void sequencer_init_preview_region(ARegion *region)
+void sequencer_init_preview_region(ARegion *region)
 {
   /* XXX a bit ugly still, copied from space_sequencer */
   /* NOTE: if you change values here, also change them in space_sequencer.c, sequencer_new */
diff --git a/source/blender/blenloader/intern/versioning_300.cc b/source/blender/blenloader/intern/versioning_300.cc
index ad7459e3d67..9ac33d9e618 100644
--- a/source/blender/blenloader/intern/versioning_300.cc
+++ b/source/blender/blenloader/intern/versioning_300.cc
@@ -2277,10 +2277,20 @@ static void version_ensure_missing_regions(ScrArea *area, SpaceLink *sl)
       break;
     }
     case SPACE_SEQ: {
+      ARegion *region;
+
       do_versions_ensure_region(regionbase,
                                 RGN_TYPE_CHANNELS,
                                 "versioning: channels region for sequencer",
                                 RGN_TYPE_TOOLS);
+
+      region = do_versions_ensure_region(regionbase,
+                                         RGN_TYPE_PREVIEW,
+                                         "versioning: preview region for sequencer",
+                                         RGN_TYPE_CHANNELS);
+      sequencer_init_preview_region(region);
+      region->flag &= ~RGN_FLAG_HIDDEN;
+
       break;
     }
   }
diff --git a/source/blender/blenloader/intern/versioning_common.h b/source/blender/blenloader/intern/versioning_common.h
index 8d17e9db39f..8c142707fdd 100644
--- a/source/blender/blenloader/intern/versioning_common.h
+++ b/source/blender/blenloader/intern/versioning_common.h
@@ -108,6 +108,8 @@ struct bNodeSocket *version_node_add_socket_if_not_exist(struct bNodeTree *ntree
 void version_socket_update_is_used(bNodeTree *ntree);
 ARegion *do_versions_add_region(int regiontype, const char *name);
 
+void sequencer_init_preview_region(ARegion *region);
+
 #ifdef __cplusplus
 }
 #endif