Asset: Dropping Material assets on material slot under mouse cursor.

This patch allows dropping material assets from material slot under the mouse
cursor. Before this change the material slot had to be hand-picked from the
properties panel.

For consistency it is chosen to do this in any shading mode as the tooltip shows
what is exactly going to happen during release.

The feature also works for other object types than Meshes as it uses the drawn surface on the
GPU to detect the material slots. Performance of this patch has been tested with AMD GCN3.0
cards and are very responsive.

Reviewed By: fclem, Severin

Differential Revision: https://developer.blender.org/D12190

4 files changed, 89 insertions, 28 deletions

diff --git a/source/blender/editors/include/ED_view3d.h b/source/blender/editors/include/ED_view3d.h
index 2c958d282f9..cf8dcbd7995 100644
--- a/source/blender/editors/include/ED_view3d.h
+++ b/source/blender/editors/include/ED_view3d.h
@@ -566,6 +566,13 @@ eV3DSelectObjectFilter ED_view3d_select_filter_from_mode(const struct Scene *sce
 void view3d_opengl_select_cache_begin(void);
 void view3d_opengl_select_cache_end(void);
 
+int view3d_opengl_select_ex(struct ViewContext *vc,
+                            unsigned int *buffer,
+                            unsigned int bufsize,
+                            const struct rcti *input,
+                            eV3DSelectMode select_mode,
+                            eV3DSelectObjectFilter select_filter,
+                            const bool do_material_slot_selection);
 int view3d_opengl_select(struct ViewContext *vc,
                          unsigned int *buffer,
                          unsigned int bufsize,
@@ -638,6 +645,9 @@ void ED_view3d_draw_setup_view(const struct wmWindowManager *wm,
 
 struct Base *ED_view3d_give_base_under_cursor(struct bContext *C, const int mval[2]);
 struct Object *ED_view3d_give_object_under_cursor(struct bContext *C, const int mval[2]);
+struct Object *ED_view3d_give_material_slot_under_cursor(struct bContext *C,
+                                                         const int mval[2],
+                                                         int *r_material_slot);
 bool ED_view3d_is_object_under_cursor(struct bContext *C, const int mval[2]);
 void ED_view3d_quadview_update(struct ScrArea *area, struct ARegion *region, bool do_clip);
 void ED_view3d_update_viewmat(struct Depsgraph *depsgraph,
diff --git a/source/blender/editors/object/object_relations.c b/source/blender/editors/object/object_relations.c
index ec72ff11683..75269dffec8 100644
--- a/source/blender/editors/object/object_relations.c
+++ b/source/blender/editors/object/object_relations.c
@@ -2729,25 +2729,26 @@ char *ED_object_ot_drop_named_material_tooltip(bContext *C,
                                                PointerRNA *properties,
                                                const wmEvent *event)
 {
-  Object *ob = ED_view3d_give_object_under_cursor(C, event->mval);
+  int mat_slot = 0;
+  Object *ob = ED_view3d_give_material_slot_under_cursor(C, event->mval, &mat_slot);
   if (ob == NULL) {
     return BLI_strdup("");
   }
+  mat_slot = max_ii(mat_slot, 1);
 
   char name[MAX_ID_NAME - 2];
   RNA_string_get(properties, "name", name);
 
-  int active_mat_slot = max_ii(ob->actcol, 1);
-  Material *prev_mat = BKE_object_material_get(ob, active_mat_slot);
+  Material *prev_mat = BKE_object_material_get(ob, mat_slot);
 
   char *result;
   if (prev_mat) {
     const char *tooltip = TIP_("Drop %s on %s (slot %d, replacing %s)");
-    result = BLI_sprintfN(tooltip, name, ob->id.name + 2, active_mat_slot, prev_mat->id.name + 2);
+    result = BLI_sprintfN(tooltip, name, ob->id.name + 2, mat_slot, prev_mat->id.name + 2);
   }
   else {
     const char *tooltip = TIP_("Drop %s on %s (slot %d)");
-    result = BLI_sprintfN(tooltip, name, ob->id.name + 2, active_mat_slot);
+    result = BLI_sprintfN(tooltip, name, ob->id.name + 2, mat_slot);
   }
   return result;
 }
@@ -2755,7 +2756,10 @@ char *ED_object_ot_drop_named_material_tooltip(bContext *C,
 static int drop_named_material_invoke(bContext *C, wmOperator *op, const wmEvent *event)
 {
   Main *bmain = CTX_data_main(C);
-  Object *ob = ED_view3d_give_object_under_cursor(C, event->mval);
+  int mat_slot = 0;
+  Object *ob = ED_view3d_give_material_slot_under_cursor(C, event->mval, &mat_slot);
+  mat_slot = max_ii(mat_slot, 1);
+
   Material *ma;
   char name[MAX_ID_NAME - 2];
 
@@ -2765,9 +2769,7 @@ static int drop_named_material_invoke(bContext *C, wmOperator *op, const wmEvent
     return OPERATOR_CANCELLED;
   }
 
-  const short active_mat_slot = ob->actcol;
-
-  BKE_object_material_assign(CTX_data_main(C), ob, ma, active_mat_slot, BKE_MAT_ASSIGN_USERPREF);
+  BKE_object_material_assign(CTX_data_main(C), ob, ma, mat_slot, BKE_MAT_ASSIGN_USERPREF);
 
   DEG_id_tag_update(&ob->id, ID_RECALC_TRANSFORM);
 
diff --git a/source/blender/editors/space_view3d/view3d_select.c b/source/blender/editors/space_view3d/view3d_select.c
index e3f97dd1c63..ff98762e373 100644
--- a/source/blender/editors/space_view3d/view3d_select.c
+++ b/source/blender/editors/space_view3d/view3d_select.c
@@ -1953,7 +1953,8 @@ static int mixed_bones_object_selectbuffer(ViewContext *vc,
                                            const int mval[2],
                                            eV3DSelectObjectFilter select_filter,
                                            bool do_nearest,
-                                           bool do_nearest_xray_if_supported)
+                                           bool do_nearest_xray_if_supported,
+                                           const bool do_material_slot_selection)
 {
   rcti rect;
   int hits15, hits9 = 0, hits5 = 0;
@@ -1972,7 +1973,8 @@ static int mixed_bones_object_selectbuffer(ViewContext *vc,
   view3d_opengl_select_cache_begin();
 
   BLI_rcti_init_pt_radius(&rect, mval, 14);
-  hits15 = view3d_opengl_select(vc, buffer, MAXPICKBUF, &rect, select_mode, select_filter);
+  hits15 = view3d_opengl_select_ex(
+      vc, buffer, MAXPICKBUF, &rect, select_mode, select_filter, do_material_slot_selection);
   if (hits15 == 1) {
     hits = selectbuffer_ret_hits_15(buffer, hits15);
     goto finally;
@@ -2071,7 +2073,8 @@ static int mixed_bones_object_selectbuffer_extended(ViewContext *vc,
 
   do_nearest = do_nearest && !enumerate;
 
-  int hits = mixed_bones_object_selectbuffer(vc, buffer, mval, select_filter, do_nearest, true);
+  int hits = mixed_bones_object_selectbuffer(
+      vc, buffer, mval, select_filter, do_nearest, true, false);
 
   return hits;
 }
@@ -2088,12 +2091,14 @@ static Base *mouse_select_eval_buffer(ViewContext *vc,
                                       int hits,
                                       Base *startbase,
                                       bool has_bones,
-                                      bool do_nearest)
+                                      bool do_nearest,
+                                      int *r_sub_selection)
 {
   ViewLayer *view_layer = vc->view_layer;
   View3D *v3d = vc->v3d;
   Base *base, *basact = NULL;
   int a;
+  int sub_selection_id = 0;
 
   if (do_nearest) {
     uint min = 0xFFFFFFFF;
@@ -2105,6 +2110,7 @@ static Base *mouse_select_eval_buffer(ViewContext *vc,
         if (min > buffer[4 * a + 1] && (buffer[4 * a + 3] & 0xFFFF0000)) {
           min = buffer[4 * a + 1];
           selcol = buffer[4 * a + 3] & 0xFFFF;
+          sub_selection_id = (buffer[4 * a + 3] & 0xFFFF0000) >> 16;
         }
       }
     }
@@ -2118,6 +2124,7 @@ static Base *mouse_select_eval_buffer(ViewContext *vc,
         if (min > buffer[4 * a + 1] && notcol != (buffer[4 * a + 3] & 0xFFFF)) {
           min = buffer[4 * a + 1];
           selcol = buffer[4 * a + 3] & 0xFFFF;
+          sub_selection_id = (buffer[4 * a + 3] & 0xFFFF0000) >> 16;
         }
       }
     }
@@ -2184,11 +2191,16 @@ static Base *mouse_select_eval_buffer(ViewContext *vc,
     }
   }
 
+  if (basact && r_sub_selection) {
+    *r_sub_selection = sub_selection_id;
+  }
+
   return basact;
 }
 
-/* mval comes from event->mval, only use within region handlers */
-Base *ED_view3d_give_base_under_cursor(bContext *C, const int mval[2])
+static Base *ed_view3d_give_base_under_cursor_ex(bContext *C,
+                                                 const int mval[2],
+                                                 int *r_material_slot)
 {
   Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
   ViewContext vc;
@@ -2202,18 +2214,30 @@ Base *ED_view3d_give_base_under_cursor(bContext *C, const int mval[2])
   ED_view3d_viewcontext_init(C, &vc, depsgraph);
 
   const bool do_nearest = !XRAY_ACTIVE(vc.v3d);
+  const bool do_material_slot_selection = r_material_slot != NULL;
   const int hits = mixed_bones_object_selectbuffer(
-      &vc, buffer, mval, VIEW3D_SELECT_FILTER_NOP, do_nearest, false);
+      &vc, buffer, mval, VIEW3D_SELECT_FILTER_NOP, do_nearest, false, do_material_slot_selection);
 
   if (hits > 0) {
-    const bool has_bones = selectbuffer_has_bones(buffer, hits);
-    basact = mouse_select_eval_buffer(
-        &vc, buffer, hits, vc.view_layer->object_bases.first, has_bones, do_nearest);
+    const bool has_bones = (r_material_slot == NULL) && selectbuffer_has_bones(buffer, hits);
+    basact = mouse_select_eval_buffer(&vc,
+                                      buffer,
+                                      hits,
+                                      vc.view_layer->object_bases.first,
+                                      has_bones,
+                                      do_nearest,
+                                      r_material_slot);
   }
 
   return basact;
 }
 
+/* mval comes from event->mval, only use within region handlers */
+Base *ED_view3d_give_base_under_cursor(bContext *C, const int mval[2])
+{
+  return ed_view3d_give_base_under_cursor_ex(C, mval, NULL);
+}
+
 Object *ED_view3d_give_object_under_cursor(bContext *C, const int mval[2])
 {
   Base *base = ED_view3d_give_base_under_cursor(C, mval);
@@ -2223,6 +2247,17 @@ Object *ED_view3d_give_object_under_cursor(bContext *C, const int mval[2])
   return NULL;
 }
 
+struct Object *ED_view3d_give_material_slot_under_cursor(struct bContext *C,
+                                                         const int mval[2],
+                                                         int *r_material_slot)
+{
+  Base *base = ed_view3d_give_base_under_cursor_ex(C, mval, r_material_slot);
+  if (base) {
+    return base->object;
+  }
+  return NULL;
+}
+
 bool ED_view3d_is_object_under_cursor(bContext *C, const int mval[2])
 {
   return ED_view3d_give_object_under_cursor(C, mval) != NULL;
@@ -2374,7 +2409,8 @@ static bool ed_object_select_pick(bContext *C,
         }
       }
       else {
-        basact = mouse_select_eval_buffer(&vc, buffer, hits, startbase, has_bones, do_nearest);
+        basact = mouse_select_eval_buffer(
+            &vc, buffer, hits, startbase, has_bones, do_nearest, NULL);
       }
 
       if (has_bones && basact) {
@@ -2436,7 +2472,7 @@ static bool ed_object_select_pick(bContext *C,
             if (!changed) {
               /* fallback to regular object selection if no new bundles were selected,
                * allows to select object parented to reconstruction object */
-              basact = mouse_select_eval_buffer(&vc, buffer, hits, startbase, 0, do_nearest);
+              basact = mouse_select_eval_buffer(&vc, buffer, hits, startbase, 0, do_nearest, NULL);
             }
           }
         }
@@ -2677,7 +2713,7 @@ static int view3d_select_exec(bContext *C, wmOperator *op)
 
         uint buffer[MAXPICKBUF];
         const int hits = mixed_bones_object_selectbuffer(
-            &vc, buffer, location, VIEW3D_SELECT_FILTER_NOP, false, true);
+            &vc, buffer, location, VIEW3D_SELECT_FILTER_NOP, false, true, false);
         retval = bone_mouse_select_menu(C, buffer, hits, true, extend, deselect, toggle);
       }
       if (!retval) {
diff --git a/source/blender/editors/space_view3d/view3d_view.c b/source/blender/editors/space_view3d/view3d_view.c
index 86a610f8dd9..b9f3706b084 100644
--- a/source/blender/editors/space_view3d/view3d_view.c
+++ b/source/blender/editors/space_view3d/view3d_view.c
@@ -964,12 +964,13 @@ static bool drw_select_filter_object_mode_lock_for_weight_paint(Object *ob, void
  *
  * \note (vc->obedit == NULL) can be set to explicitly skip edit-object selection.
  */
-int view3d_opengl_select(ViewContext *vc,
-                         uint *buffer,
-                         uint bufsize,
-                         const rcti *input,
-                         eV3DSelectMode select_mode,
-                         eV3DSelectObjectFilter select_filter)
+int view3d_opengl_select_ex(ViewContext *vc,
+                            uint *buffer,
+                            uint bufsize,
+                            const rcti *input,
+                            eV3DSelectMode select_mode,
+                            eV3DSelectObjectFilter select_filter,
+                            const bool do_material_slot_selection)
 {
   struct bThemeState theme_state;
   const wmWindowManager *wm = CTX_wm_manager(vc->C);
@@ -1119,6 +1120,7 @@ int view3d_opengl_select(ViewContext *vc,
                          use_obedit_skip,
                          draw_surface,
                          use_nearest,
+                         do_material_slot_selection,
                          &rect,
                          drw_select_loop_pass,
                          &drw_select_loop_user_data,
@@ -1149,6 +1151,7 @@ int view3d_opengl_select(ViewContext *vc,
                          use_obedit_skip,
                          draw_surface,
                          use_nearest,
+                         do_material_slot_selection,
                          &rect,
                          drw_select_loop_pass,
                          &drw_select_loop_user_data,
@@ -1178,6 +1181,16 @@ finally:
   return hits;
 }
 
+int view3d_opengl_select(ViewContext *vc,
+                         uint *buffer,
+                         uint bufsize,
+                         const rcti *input,
+                         eV3DSelectMode select_mode,
+                         eV3DSelectObjectFilter select_filter)
+{
+  return view3d_opengl_select_ex(vc, buffer, bufsize, input, select_mode, select_filter, false);
+}
+
 int view3d_opengl_select_with_id_filter(ViewContext *vc,
                                         uint *buffer,
                                         uint bufsize,