Fix T73871: improve assignement of material to selection in multi object

editmode

This was already supported in "Select" & "Deselect" but not in "Assign".
So similar to rB6b39dc7672eb, we now check if the material corresponding
to the currently selected material slot is found in other objects
materials and assign this (instead of always assigning their 'own'
actcol).

Maniphest Tasks: T73871

Differential Revision: https://developer.blender.org/D6869

1 files changed, 29 insertions, 4 deletions

diff --git a/source/blender/editors/render/render_shading.c b/source/blender/editors/render/render_shading.c
index 95bc90c8e5f..8ecaeefbd5f 100644
--- a/source/blender/editors/render/render_shading.c
+++ b/source/blender/editors/render/render_shading.c
@@ -217,13 +217,38 @@ static int material_slot_assign_exec(bContext *C, wmOperator *UNUSED(op))
   View3D *v3d = CTX_wm_view3d(C);
   bool changed_multi = false;
 
+  Object *obact = CTX_data_active_object(C);
+  const Material *mat_active = obact ? BKE_object_material_get(obact, obact->actcol) : NULL;
+
   uint objects_len = 0;
   Object **objects = object_array_for_shading(C, &objects_len);
   for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
     Object *ob = objects[ob_index];
-    if (ob->actcol <= 0) {
+    short mat_nr_active = -1;
+
+    if (ob->totcol == 0) {
       continue;
     }
+    if (obact && (mat_active == BKE_object_material_get(ob, obact->actcol))) {
+      /* Avoid searching since there may be multiple slots with the same material.
+       * For the active object or duplicates: match the material slot index first. */
+      mat_nr_active = obact->actcol - 1;
+    }
+    else {
+      /* Find the first matching material.
+       * Note: there may be multiple but that's not a common use case. */
+      for (short i = 0; i < ob->totcol; i++) {
+        const Material *mat = BKE_object_material_get(ob, i + 1);
+        if (mat_active == mat) {
+          mat_nr_active = i;
+          break;
+        }
+      }
+      if (mat_nr_active == -1) {
+        continue;
+      }
+    }
+
     bool changed = false;
     if (ob->type == OB_MESH) {
       BMEditMesh *em = BKE_editmesh_from_object(ob);
@@ -234,7 +259,7 @@ static int material_slot_assign_exec(bContext *C, wmOperator *UNUSED(op))
         BM_ITER_MESH (efa, &iter, em->bm, BM_FACES_OF_MESH) {
           if (BM_elem_flag_test(efa, BM_ELEM_SELECT)) {
             changed = true;
-            efa->mat_nr = ob->actcol - 1;
+            efa->mat_nr = mat_nr_active;
           }
         }
       }
@@ -247,7 +272,7 @@ static int material_slot_assign_exec(bContext *C, wmOperator *UNUSED(op))
         for (nu = nurbs->first; nu; nu = nu->next) {
           if (ED_curve_nurb_select_check(v3d, nu)) {
             changed = true;
-            nu->mat_nr = ob->actcol - 1;
+            nu->mat_nr = mat_nr_active;
           }
         }
       }
@@ -259,7 +284,7 @@ static int material_slot_assign_exec(bContext *C, wmOperator *UNUSED(op))
       if (ef && BKE_vfont_select_get(ob, &selstart, &selend)) {
         for (i = selstart; i <= selend; i++) {
           changed = true;
-          ef->textbufinfo[i].mat_nr = ob->actcol;
+          ef->textbufinfo[i].mat_nr = mat_nr_active + 1;
         }
       }
     }