Fix (unreported) design flow in how workspace's relation data are read from .blend file.

Relying on pointer addresses across different data-blocks is extremely
not recommended (and should be strictly forbidden ideally), in
particular in direct_link step of blend file reading.
- It assumes a specific order in reading of data, which is not ensured
  in future, and is in any case a very bad, non explicit, hidden
  dependency on behaviors of other parts of the codebase.
- It is intrinsically unsafe (as in, it makes writing bad code and making
  mistakes easy, see e.g. fix in rB84b3f6e049b35f9).
- It makes advanced handling of data-blocks harder (thinking about
  partial undo code e.g., even though in this specific case it was not
  an issue as we do not re-read neither windowmanagers nor worspaces
  during undo).

New code uses windows' `winid` instead as 'anchor' to find again proper
workspace hook in windows at read time.

As a bonus, it will also cleanup the list of relations from any invalid
ones (afaict it was never done previously).

Differential Revision: https://developer.blender.org/D9073

10 files changed, 91 insertions, 30 deletions

diff --git a/source/blender/blenkernel/BKE_workspace.h b/source/blender/blenkernel/BKE_workspace.h
index 5ff1ba2c6f5..82a4e5fe08e 100644
--- a/source/blender/blenkernel/BKE_workspace.h
+++ b/source/blender/blenkernel/BKE_workspace.h
@@ -36,7 +36,8 @@ struct bToolRef;
 struct WorkSpace *BKE_workspace_add(struct Main *bmain, const char *name);
 void BKE_workspace_remove(struct Main *bmain, struct WorkSpace *workspace);
 
-struct WorkSpaceInstanceHook *BKE_workspace_instance_hook_create(const struct Main *bmain);
+struct WorkSpaceInstanceHook *BKE_workspace_instance_hook_create(const struct Main *bmain,
+                                                                 const int winid);
 void BKE_workspace_instance_hook_free(const struct Main *bmain,
                                       struct WorkSpaceInstanceHook *hook);
 
@@ -83,11 +84,13 @@ void BKE_workspace_active_set(struct WorkSpaceInstanceHook *hook,
 struct WorkSpaceLayout *BKE_workspace_active_layout_get(const struct WorkSpaceInstanceHook *hook)
     GETTER_ATTRS;
 void BKE_workspace_active_layout_set(struct WorkSpaceInstanceHook *hook,
+                                     const int winid,
                                      struct WorkSpace *workspace,
                                      struct WorkSpaceLayout *layout) SETTER_ATTRS;
 struct bScreen *BKE_workspace_active_screen_get(const struct WorkSpaceInstanceHook *hook)
     GETTER_ATTRS;
 void BKE_workspace_active_screen_set(struct WorkSpaceInstanceHook *hook,
+                                     const int winid,
                                      struct WorkSpace *workspace,
                                      struct bScreen *screen) SETTER_ATTRS;
 
diff --git a/source/blender/blenkernel/intern/workspace.c b/source/blender/blenkernel/intern/workspace.c
index 324c8db0fe9..775d83278e9 100644
--- a/source/blender/blenkernel/intern/workspace.c
+++ b/source/blender/blenkernel/intern/workspace.c
@@ -125,10 +125,14 @@ static WorkSpaceLayout *workspace_layout_find_exec(const WorkSpace *workspace,
   return BLI_findptr(&workspace->layouts, screen, offsetof(WorkSpaceLayout, screen));
 }
 
-static void workspace_relation_add(ListBase *relation_list, void *parent, void *data)
+static void workspace_relation_add(ListBase *relation_list,
+                                   void *parent,
+                                   const int parentid,
+                                   void *data)
 {
   WorkSpaceDataRelation *relation = MEM_callocN(sizeof(*relation), __func__);
   relation->parent = parent;
+  relation->parentid = parentid;
   relation->value = data;
   /* add to head, if we switch back to it soon we find it faster. */
   BLI_addhead(relation_list, relation);
@@ -139,11 +143,15 @@ static void workspace_relation_remove(ListBase *relation_list, WorkSpaceDataRela
   MEM_freeN(relation);
 }
 
-static void workspace_relation_ensure_updated(ListBase *relation_list, void *parent, void *data)
+static void workspace_relation_ensure_updated(ListBase *relation_list,
+                                              void *parent,
+                                              const int parentid,
+                                              void *data)
 {
-  WorkSpaceDataRelation *relation = BLI_findptr(
-      relation_list, parent, offsetof(WorkSpaceDataRelation, parent));
+  WorkSpaceDataRelation *relation = BLI_listbase_bytes_find(
+      relation_list, &parentid, sizeof(parentid), offsetof(WorkSpaceDataRelation, parentid));
   if (relation != NULL) {
+    relation->parent = parent;
     relation->value = data;
     /* reinsert at the head of the list, so that more commonly used relations are found faster. */
     BLI_remlink(relation_list, relation);
@@ -151,7 +159,7 @@ static void workspace_relation_ensure_updated(ListBase *relation_list, void *par
   }
   else {
     /* no matching relation found, add new one */
-    workspace_relation_add(relation_list, parent, data);
+    workspace_relation_add(relation_list, parent, parentid, data);
   }
 }
 
@@ -219,13 +227,13 @@ void BKE_workspace_remove(Main *bmain, WorkSpace *workspace)
   BKE_id_free(bmain, workspace);
 }
 
-WorkSpaceInstanceHook *BKE_workspace_instance_hook_create(const Main *bmain)
+WorkSpaceInstanceHook *BKE_workspace_instance_hook_create(const Main *bmain, const int winid)
 {
   WorkSpaceInstanceHook *hook = MEM_callocN(sizeof(WorkSpaceInstanceHook), __func__);
 
   /* set an active screen-layout for each possible window/workspace combination */
   for (WorkSpace *workspace = bmain->workspaces.first; workspace; workspace = workspace->id.next) {
-    BKE_workspace_active_layout_set(hook, workspace, workspace->layouts.first);
+    BKE_workspace_active_layout_set(hook, winid, workspace, workspace->layouts.first);
   }
 
   return hook;
@@ -483,11 +491,12 @@ WorkSpaceLayout *BKE_workspace_active_layout_for_workspace_get(const WorkSpaceIn
  * WorkSpaceInstanceHook.act_layout should only be modified directly to update the layout pointer.
  */
 void BKE_workspace_active_layout_set(WorkSpaceInstanceHook *hook,
+                                     const int winid,
                                      WorkSpace *workspace,
                                      WorkSpaceLayout *layout)
 {
   hook->act_layout = layout;
-  workspace_relation_ensure_updated(&workspace->hook_layout_relations, hook, layout);
+  workspace_relation_ensure_updated(&workspace->hook_layout_relations, hook, winid, layout);
 }
 
 bScreen *BKE_workspace_active_screen_get(const WorkSpaceInstanceHook *hook)
@@ -495,12 +504,13 @@ bScreen *BKE_workspace_active_screen_get(const WorkSpaceInstanceHook *hook)
   return hook->act_layout->screen;
 }
 void BKE_workspace_active_screen_set(WorkSpaceInstanceHook *hook,
+                                     const int winid,
                                      WorkSpace *workspace,
                                      bScreen *screen)
 {
   /* we need to find the WorkspaceLayout that wraps this screen */
   WorkSpaceLayout *layout = BKE_workspace_layout_find(hook->active, screen);
-  BKE_workspace_active_layout_set(hook, workspace, layout);
+  BKE_workspace_active_layout_set(hook, winid, workspace, layout);
 }
 
 const char *BKE_workspace_layout_name_get(const WorkSpaceLayout *layout)
diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 1072cd3686e..aa2f103c693 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -1794,7 +1794,7 @@ static void *newdataadr_no_us(FileData *fd, const void *adr)
 }
 
 /* direct datablocks with global linking */
-static void *newglobadr(FileData *fd, const void *adr)
+void *blo_read_get_new_globaldata_address(FileData *fd, const void *adr)
 {
   return oldnewmap_lookup_and_inc(fd->globmap, adr, true);
 }
@@ -2553,6 +2553,21 @@ static void lib_link_workspaces(BlendLibReader *reader, WorkSpace *workspace)
 {
   ID *id = (ID *)workspace;
 
+  /* Restore proper 'parent' pointers to relevant data, and clean up unused/invalid entries. */
+  LISTBASE_FOREACH_MUTABLE (WorkSpaceDataRelation *, relation, &workspace->hook_layout_relations) {
+    relation->parent = NULL;
+    LISTBASE_FOREACH (wmWindowManager *, wm, &reader->main->wm) {
+      LISTBASE_FOREACH (wmWindow *, win, &wm->windows) {
+        if (win->winid == relation->parentid) {
+          relation->parent = win->workspace_hook;
+        }
+      }
+    }
+    if (relation->parent == NULL) {
+      BLI_freelinkN(&workspace->hook_layout_relations, relation);
+    }
+  }
+
   LISTBASE_FOREACH_MUTABLE (WorkSpaceLayout *, layout, &workspace->layouts) {
     BLO_read_id_address(reader, id->lib, &layout->screen);
 
@@ -2581,12 +2596,8 @@ static void direct_link_workspace(BlendDataReader *reader, WorkSpace *workspace)
   BLO_read_list(reader, &workspace->tools);
 
   LISTBASE_FOREACH (WorkSpaceDataRelation *, relation, &workspace->hook_layout_relations) {
-    /* data from window - need to access through global oldnew-map */
-    /* XXX This is absolutely not acceptable. There is no acceptable reasons to mess with other
-     * ID's data in read code, and certainly never, ever in `direct_link_` functions.
-     * Kept for now because it seems to work, but it should be refactored. Probably store and use
-     * window's `winid`, just like it was already done for screens? */
-    relation->parent = newglobadr(reader->fd, relation->parent);
+    /* parent pointer does not belong to workspace data and is therefore restored in lib_link step
+     * of window manager.*/
     BLO_read_data_address(reader, &relation->value);
   }
 
@@ -5472,8 +5483,9 @@ static void direct_link_windowmanager(BlendDataReader *reader, wmWindowManager *
     WorkSpaceInstanceHook *hook = win->workspace_hook;
     BLO_read_data_address(reader, &win->workspace_hook);
 
-    /* we need to restore a pointer to this later when reading workspaces,
-     * so store in global oldnew-map. */
+    /* We need to restore a pointer to this later when reading workspaces,
+     * so store in global oldnew-map.
+     * Note that this is only needed for versionning of older .blend files now.. */
     oldnewmap_insert(reader->fd->globmap, hook, win->workspace_hook, 0);
 
     direct_link_area_map(reader, &win->global_areas);
@@ -6847,7 +6859,7 @@ static BHead *read_global(BlendFileData *bfd, FileData *fd, BHead *bhead)
 /* note, this has to be kept for reading older files... */
 static void link_global(FileData *fd, BlendFileData *bfd)
 {
-  bfd->cur_view_layer = newglobadr(fd, bfd->cur_view_layer);
+  bfd->cur_view_layer = blo_read_get_new_globaldata_address(fd, bfd->cur_view_layer);
   bfd->curscreen = newlibadr(fd, NULL, bfd->curscreen);
   bfd->curscene = newlibadr(fd, NULL, bfd->curscene);
   // this happens in files older than 2.35
diff --git a/source/blender/blenloader/intern/readfile.h b/source/blender/blenloader/intern/readfile.h
index 2ddf96a2d47..d3372a646a9 100644
--- a/source/blender/blenloader/intern/readfile.h
+++ b/source/blender/blenloader/intern/readfile.h
@@ -203,3 +203,7 @@ void do_versions_after_linking_270(struct Main *bmain);
 void do_versions_after_linking_280(struct Main *bmain, struct ReportList *reports);
 void do_versions_after_linking_290(struct Main *bmain, struct ReportList *reports);
 void do_versions_after_linking_cycles(struct Main *bmain);
+
+/* This is rather unfortunate to have to expose this here, but better use that nasty hack in
+ * do_version than readfile itself. */
+void *blo_read_get_new_globaldata_address(struct FileData *fd, const void *adr);
diff --git a/source/blender/blenloader/intern/versioning_280.c b/source/blender/blenloader/intern/versioning_280.c
index 14a4643f760..b7c48234590 100644
--- a/source/blender/blenloader/intern/versioning_280.c
+++ b/source/blender/blenloader/intern/versioning_280.c
@@ -241,7 +241,7 @@ static void do_version_workspaces_after_lib_link(Main *bmain)
       if (screen->temp) {
         /* We do not generate a new workspace for those screens...
          * still need to set some data in win. */
-        win->workspace_hook = BKE_workspace_instance_hook_create(bmain);
+        win->workspace_hook = BKE_workspace_instance_hook_create(bmain, win->winid);
         win->scene = screen->scene;
         /* Deprecated from now on! */
         win->screen = NULL;
@@ -254,10 +254,10 @@ static void do_version_workspaces_after_lib_link(Main *bmain)
       WorkSpaceLayout *layout = BKE_workspace_layout_find(workspace, win->screen);
       BLI_assert(layout != NULL);
 
-      win->workspace_hook = BKE_workspace_instance_hook_create(bmain);
+      win->workspace_hook = BKE_workspace_instance_hook_create(bmain, win->winid);
 
       BKE_workspace_active_set(win->workspace_hook, workspace);
-      BKE_workspace_active_layout_set(win->workspace_hook, workspace, layout);
+      BKE_workspace_active_layout_set(win->workspace_hook, win->winid, workspace, layout);
 
       /* Move scene and view layer to window. */
       Scene *scene = screen->scene;
diff --git a/source/blender/blenloader/intern/versioning_290.c b/source/blender/blenloader/intern/versioning_290.c
index 400403a4636..48ae5963da8 100644
--- a/source/blender/blenloader/intern/versioning_290.c
+++ b/source/blender/blenloader/intern/versioning_290.c
@@ -41,6 +41,7 @@
 #include "DNA_rigidbody_types.h"
 #include "DNA_screen_types.h"
 #include "DNA_shader_fx_types.h"
+#include "DNA_workspace_types.h"
 
 #include "BKE_collection.h"
 #include "BKE_colortools.h"
@@ -779,5 +780,31 @@ void blo_do_versions_290(FileData *fd, Library *UNUSED(lib), Main *bmain)
    */
   {
     /* Keep this block, even when empty. */
+    if (!DNA_struct_elem_find(fd->filesdna, "WorkSpaceDataRelation", "int", "parentid")) {
+      LISTBASE_FOREACH (WorkSpace *, workspace, &bmain->workspaces) {
+        LISTBASE_FOREACH_MUTABLE (
+            WorkSpaceDataRelation *, relation, &workspace->hook_layout_relations) {
+          relation->parent = blo_read_get_new_globaldata_address(fd, relation->parent);
+          BLI_assert(relation->parentid == 0);
+          if (relation->parent != NULL) {
+            LISTBASE_FOREACH (wmWindowManager *, wm, &bmain->wm) {
+              wmWindow *win = BLI_findptr(
+                  &wm->windows, relation->parent, offsetof(wmWindow, workspace_hook));
+              if (win != NULL) {
+                relation->parentid = win->winid;
+                break;
+              }
+            }
+            if (relation->parentid == 0) {
+              BLI_assert(
+                  !"Found a valid parent for workspace data relation, but no valid parent id.");
+            }
+          }
+          if (relation->parentid == 0) {
+            BLI_freelinkN(&workspace->hook_layout_relations, relation);
+          }
+        }
+      }
+    }
   }
 }
diff --git a/source/blender/editors/screen/workspace_edit.c b/source/blender/editors/screen/workspace_edit.c
index 702c824077d..aca2b48a937 100644
--- a/source/blender/editors/screen/workspace_edit.c
+++ b/source/blender/editors/screen/workspace_edit.c
@@ -141,7 +141,7 @@ bool ED_workspace_change(WorkSpace *workspace_new, bContext *C, wmWindowManager
     return false;
   }
 
-  BKE_workspace_active_layout_set(win->workspace_hook, workspace_new, layout_new);
+  BKE_workspace_active_layout_set(win->workspace_hook, win->winid, workspace_new, layout_new);
   BKE_workspace_active_set(win->workspace_hook, workspace_new);
 
   /* update screen *after* changing workspace - which also causes the
diff --git a/source/blender/makesdna/DNA_workspace_types.h b/source/blender/makesdna/DNA_workspace_types.h
index 170366881c6..b9ca2598ff3 100644
--- a/source/blender/makesdna/DNA_workspace_types.h
+++ b/source/blender/makesdna/DNA_workspace_types.h
@@ -160,10 +160,15 @@ typedef struct WorkSpaceDataRelation {
   struct WorkSpaceDataRelation *next, *prev;
 
   /** The data used to identify the relation
-   * (e.g. to find screen-layout (= value) from/for a hook). */
+   * (e.g. to find screen-layout (= value) from/for a hook).
+   * Note: Now runtime only. */
   void *parent;
   /** The value for this parent-data/workspace relation. */
   void *value;
+
+  /** Reference to the actual parent window, wmWindow->winid. Used in read/write code. */
+  int parentid;
+  char _pad_0[4];
 } WorkSpaceDataRelation;
 
 /**
diff --git a/source/blender/windowmanager/intern/wm.c b/source/blender/windowmanager/intern/wm.c
index a14ccfa104c..db937737d07 100644
--- a/source/blender/windowmanager/intern/wm.c
+++ b/source/blender/windowmanager/intern/wm.c
@@ -395,7 +395,7 @@ void wm_add_default(Main *bmain, bContext *C)
   win->scene = CTX_data_scene(C);
   STRNCPY(win->view_layer_name, CTX_data_view_layer(C)->name);
   BKE_workspace_active_set(win->workspace_hook, workspace);
-  BKE_workspace_active_layout_set(win->workspace_hook, workspace, layout);
+  BKE_workspace_active_layout_set(win->workspace_hook, win->winid, workspace, layout);
   screen->winid = win->winid;
 
   wm->winactive = win;
diff --git a/source/blender/windowmanager/intern/wm_window.c b/source/blender/windowmanager/intern/wm_window.c
index 610a06690cc..e8575374022 100644
--- a/source/blender/windowmanager/intern/wm_window.c
+++ b/source/blender/windowmanager/intern/wm_window.c
@@ -297,7 +297,7 @@ wmWindow *wm_window_new(const Main *bmain, wmWindowManager *wm, wmWindow *parent
   /* Dialogs may have a child window as parent. Otherwise, a child must not be a parent too. */
   win->parent = (!dialog && parent && parent->parent) ? parent->parent : parent;
   win->stereo3d_format = MEM_callocN(sizeof(Stereo3dFormat), "Stereo 3D Format (window)");
-  win->workspace_hook = BKE_workspace_instance_hook_create(bmain);
+  win->workspace_hook = BKE_workspace_instance_hook_create(bmain, win->winid);
 
   return win;
 }
@@ -327,7 +327,7 @@ wmWindow *wm_window_copy(Main *bmain,
   layout_new = duplicate_layout ?
                    ED_workspace_layout_duplicate(bmain, workspace, layout_old, win_dst) :
                    layout_old;
-  BKE_workspace_active_layout_set(win_dst->workspace_hook, workspace, layout_new);
+  BKE_workspace_active_layout_set(win_dst->workspace_hook, win_dst->winid, workspace, layout_new);
 
   *win_dst->stereo3d_format = *win_src->stereo3d_format;
 
@@ -2420,7 +2420,7 @@ WorkSpaceLayout *WM_window_get_active_layout(const wmWindow *win)
 }
 void WM_window_set_active_layout(wmWindow *win, WorkSpace *workspace, WorkSpaceLayout *layout)
 {
-  BKE_workspace_active_layout_set(win->workspace_hook, workspace, layout);
+  BKE_workspace_active_layout_set(win->workspace_hook, win->winid, workspace, layout);
 }
 
 /**
@@ -2434,7 +2434,7 @@ bScreen *WM_window_get_active_screen(const wmWindow *win)
 }
 void WM_window_set_active_screen(wmWindow *win, WorkSpace *workspace, bScreen *screen)
 {
-  BKE_workspace_active_screen_set(win->workspace_hook, workspace, screen);
+  BKE_workspace_active_screen_set(win->workspace_hook, win->winid, workspace, screen);
 }
 
 bool WM_window_is_temp_screen(const wmWindow *win)