1 files changed, 94 insertions, 1 deletions

diff --git a/source/blender/windowmanager/intern/wm_uilist_type.c b/source/blender/windowmanager/intern/wm_uilist_type.c
index 45c14c0bbe9..82ba4aa6e6f 100644
--- a/source/blender/windowmanager/intern/wm_uilist_type.c
+++ b/source/blender/windowmanager/intern/wm_uilist_type.c
@@ -21,16 +21,24 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 
+#include "BLI_listbase.h"
 #include "BLI_sys_types.h"
 
+#include "DNA_space_types.h"
 #include "DNA_windowmanager_types.h"
 
 #include "MEM_guardedalloc.h"
 
+#include "UI_interface.h"
+
 #include "BLI_ghash.h"
+#include "BLI_listbase.h"
+#include "BLI_string.h"
 #include "BLI_utildefines.h"
 
+#include "BKE_main.h"
 #include "BKE_screen.h"
 
 #include "WM_api.h"
@@ -60,8 +68,62 @@ bool WM_uilisttype_add(uiListType *ult)
   return 1;
 }
 
-void WM_uilisttype_freelink(uiListType *ult)
+static void wm_uilisttype_unlink_from_region(const uiListType *ult, ARegion *region)
 {
+  LISTBASE_FOREACH (uiList *, list, &region->ui_lists) {
+    if (list->type == ult) {
+      /* Don't delete the list, it's not just runtime data but stored in files. Freeing would make
+       * that data get lost. */
+      list->type = NULL;
+    }
+  }
+}
+
+static void wm_uilisttype_unlink_from_area(const uiListType *ult, ScrArea *area)
+{
+  LISTBASE_FOREACH (SpaceLink *, space_link, &area->spacedata) {
+    ListBase *regionbase = (space_link == area->spacedata.first) ? &area->regionbase :
+                                                                   &space_link->regionbase;
+    LISTBASE_FOREACH (ARegion *, region, regionbase) {
+      wm_uilisttype_unlink_from_region(ult, region);
+    }
+  }
+}
+
+/**
+ * For all lists representing \a ult, clear their `uiListType` pointer. Use when a list-type is
+ * deleted, so that the UI doesn't keep references to it.
+ *
+ * This is a common pattern for unregistering (usually .py defined) types at runtime, e.g. see
+ * #WM_gizmomaptype_group_unlink().
+ * Note that unlike in some other cases using this pattern, we don't actually free the lists with
+ * type \a ult, we just clear the reference to the type. That's because UI-Lists are written to
+ * files and we don't want them to get lost together with their (user visible) settings.
+ */
+static void wm_uilisttype_unlink(Main *bmain, const uiListType *ult)
+{
+  for (wmWindowManager *wm = bmain->wm.first; wm != NULL; wm = wm->id.next) {
+    LISTBASE_FOREACH (wmWindow *, win, &wm->windows) {
+      LISTBASE_FOREACH (ScrArea *, global_area, &win->global_areas.areabase) {
+        wm_uilisttype_unlink_from_area(ult, global_area);
+      }
+    }
+  }
+
+  for (bScreen *screen = bmain->screens.first; screen != NULL; screen = screen->id.next) {
+    LISTBASE_FOREACH (ScrArea *, area, &screen->areabase) {
+      wm_uilisttype_unlink_from_area(ult, area);
+    }
+
+    LISTBASE_FOREACH (ARegion *, region, &screen->regionbase) {
+      wm_uilisttype_unlink_from_region(ult, region);
+    }
+  }
+}
+
+void WM_uilisttype_remove_ptr(Main *bmain, uiListType *ult)
+{
+  wm_uilisttype_unlink(bmain, ult);
 
   bool ok = BLI_ghash_remove(uilisttypes_hash, ult->idname, NULL, MEM_freeN);
 
@@ -88,3 +150,34 @@ void WM_uilisttype_free(void)
   BLI_ghash_free(uilisttypes_hash, NULL, MEM_freeN);
   uilisttypes_hash = NULL;
 }
+
+/**
+ * The "full" list-ID is an internal name used for storing and identifying a list. It is built like
+ * this:
+ * "{uiListType.idname}_{list_id}", whereby "list_id" is an optional parameter passed to
+ * `UILayout.template_list()`. If it is not set, the full list-ID is just "{uiListType.idname}_".
+ *
+ * Note that whenever the Python API refers to the list-ID, it's the short, "non-full" one it
+ * passed to `UILayout.template_list()`. C code can query that through
+ * #WM_uilisttype_list_id_get().
+ */
+void WM_uilisttype_to_full_list_id(const uiListType *ult,
+                                   const char *list_id,
+                                   char r_full_list_id[/*UI_MAX_NAME_STR*/])
+{
+  /* We tag the list id with the list type... */
+  BLI_snprintf(r_full_list_id, UI_MAX_NAME_STR, "%s_%s", ult->idname, list_id ? list_id : "");
+}
+
+/**
+ * Get the "non-full" list-ID, see #WM_uilisttype_to_full_list_id() for details.
+ *
+ * \note Assumes `uiList.list_id` was set using #WM_uilisttype_to_full_list_id()!
+ */
+const char *WM_uilisttype_list_id_get(const uiListType *ult, uiList *list)
+{
+  /* Some sanity check for the assumed behavior of #WM_uilisttype_to_full_list_id(). */
+  BLI_assert((list->list_id + strlen(ult->idname))[0] == '_');
+  /* +1 to skip the '_' */
+  return list->list_id + strlen(ult->idname) + 1;
+}