UV: tweak face select behavior

When the mouse cursor is inside the UV face,
extend the selection threshold.

This means when zoomed in, a face can always be selected when the cursor
is inside it.
In the case of multiple overlapping faces - the face with the closest
center is used.

source/blender/bmesh/intern/bmesh_query_uv.c

@@ -203,3 +203,22 @@ bool BM_edge_uv_share_vert_check(BMEdge *e, BMLoop *l_a, BMLoop *l_b, const int
 
   return true;
 }
+
+/**
+ * Check if the point is inside the UV face.
+ */
+bool BM_face_uv_point_inside_test(const BMFace *f, const float co[2], const int cd_loop_uv_offset)
+{
+  float(*projverts)[2] = BLI_array_alloca(projverts, f->len);
+
+  BMLoop *l_iter;
+  int i;
+
+  BLI_assert(BM_face_is_normal_valid(f));
+
+  for (i = 0, l_iter = BM_FACE_FIRST_LOOP(f); i < f->len; i++, l_iter = l_iter->next) {
+    copy_v2_v2(projverts[i], BM_ELEM_CD_GET_VOID_P(l_iter, cd_loop_uv_offset));
+  }
+
+  return isect_point_poly_v2(co, projverts, f->len, false);
+}

source/blender/bmesh/intern/bmesh_query_uv.h

@@ -58,3 +58,8 @@ bool BM_loop_uv_share_vert_check(BMLoop *l_a,
                                  BMLoop *l_b,
                                  const int cd_loop_uv_offset) ATTR_WARN_UNUSED_RESULT
     ATTR_NONNULL();
+
+bool BM_face_uv_point_inside_test(const BMFace *f,
+                                  const float co[2],
+                                  const int cd_loop_uv_offset) ATTR_WARN_UNUSED_RESULT
+    ATTR_NONNULL();

source/blender/editors/uvedit/uvedit_intern.h

@@ -75,33 +75,44 @@ bool uv_find_nearest_vert(struct Scene *scene,
                           struct Object *obedit,
                           const float co[2],
                           const float penalty_dist,
-                          struct UvNearestHit *hit_final);
+                          struct UvNearestHit *hit);
 bool uv_find_nearest_vert_multi(struct Scene *scene,
                                 struct Object **objects,
                                 const uint objects_len,
                                 const float co[2],
                                 const float penalty_dist,
-                                struct UvNearestHit *hit_final);
+                                struct UvNearestHit *hit);
 
 bool uv_find_nearest_edge(struct Scene *scene,
                           struct Object *obedit,
                           const float co[2],
-                          struct UvNearestHit *hit_final);
+                          struct UvNearestHit *hit);
 bool uv_find_nearest_edge_multi(struct Scene *scene,
                                 struct Object **objects,
                                 const uint objects_len,
                                 const float co[2],
-                                struct UvNearestHit *hit_final);
+                                struct UvNearestHit *hit);
 
+bool uv_find_nearest_face_ex(struct Scene *scene,
+                             struct Object *obedit,
+                             const float co[2],
+                             struct UvNearestHit *hit,
+                             struct UvNearestHit *hit_in_face);
 bool uv_find_nearest_face(struct Scene *scene,
                           struct Object *obedit,
                           const float co[2],
-                          struct UvNearestHit *hit_final);
+                          struct UvNearestHit *hit);
+bool uv_find_nearest_face_multi_ex(struct Scene *scene,
+                                   struct Object **objects,
+                                   const uint objects_len,
+                                   const float co[2],
+                                   struct UvNearestHit *hit,
+                                   struct UvNearestHit *hit_in_face);
 bool uv_find_nearest_face_multi(struct Scene *scene,
                                 struct Object **objects,
                                 const uint objects_len,
                                 const float co[2],
-                                struct UvNearestHit *hit_final);
+                                struct UvNearestHit *hit);
 
 BMLoop *uv_find_nearest_loop_from_vert(struct Scene *scene,
                                        struct Object *obedit,

source/blender/editors/uvedit/uvedit_select.c

@@ -695,6 +695,7 @@ bool uv_find_nearest_edge(Scene *scene, Object *obedit, const float co[2], UvNea
       const float dist_test_sq = len_squared_v2(delta);
 
       if (dist_test_sq < hit->dist_sq) {
+        hit->ob = obedit;
         hit->efa = efa;
 
         hit->l = l;
@@ -707,24 +708,21 @@ bool uv_find_nearest_edge(Scene *scene, Object *obedit, const float co[2], UvNea
   return found;
 }
 
-bool uv_find_nearest_edge_multi(Scene *scene,
-                                Object **objects,
-                                const uint objects_len,
-                                const float co[2],
-                                UvNearestHit *hit_final)
+bool uv_find_nearest_edge_multi(
+    Scene *scene, Object **objects, const uint objects_len, const float co[2], UvNearestHit *hit)
 {
   bool found = false;
   for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
     Object *obedit = objects[ob_index];
-    if (uv_find_nearest_edge(scene, obedit, co, hit_final)) {
-      hit_final->ob = obedit;
+    if (uv_find_nearest_edge(scene, obedit, co, hit)) {
       found = true;
     }
   }
   return found;
 }
 
-bool uv_find_nearest_face(Scene *scene, Object *obedit, const float co[2], UvNearestHit *hit)
+bool uv_find_nearest_face_ex(
+    Scene *scene, Object *obedit, const float co[2], UvNearestHit *hit, UvNearestHit *hit_in_face)
 {
   BLI_assert((hit->scale[0] > 0.0f) && (hit->scale[1] > 0.0f));
   BMEditMesh *em = BKE_editmesh_from_object(obedit);
@@ -750,29 +748,52 @@ bool uv_find_nearest_face(Scene *scene, Object *obedit, const float co[2], UvNea
     const float dist_test_sq = len_squared_v2(delta);
 
     if (dist_test_sq < hit->dist_sq) {
+      hit->ob = obedit;
       hit->efa = efa;
       hit->dist_sq = dist_test_sq;
       found = true;
     }
+
+    if (hit_in_face != NULL) {
+      if (dist_test_sq < hit_in_face->dist_sq) {
+        if (BM_face_uv_point_inside_test(efa, co, cd_loop_uv_offset)) {
+          hit_in_face->ob = obedit;
+          hit_in_face->efa = efa;
+          hit_in_face->dist_sq = dist_test_sq;
+          found = true;
+        }
+      }
+    }
+  }
+  return found;
+}
+
+bool uv_find_nearest_face(Scene *scene, Object *obedit, const float co[2], UvNearestHit *hit)
+{
+  return uv_find_nearest_face_ex(scene, obedit, co, hit, NULL);
+}
+
+bool uv_find_nearest_face_multi_ex(Scene *scene,
+                                   Object **objects,
+                                   const uint objects_len,
+                                   const float co[2],
+                                   UvNearestHit *hit,
+                                   UvNearestHit *hit_in_face)
+{
+  bool found = false;
+  for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
+    Object *obedit = objects[ob_index];
+    if (uv_find_nearest_face_ex(scene, obedit, co, hit, hit_in_face)) {
+      found = true;
+    }
   }
   return found;
 }
 
-bool uv_find_nearest_face_multi(Scene *scene,
-                                Object **objects,
-                                const uint objects_len,
-                                const float co[2],
-                                UvNearestHit *hit_final)
+bool uv_find_nearest_face_multi(
+    Scene *scene, Object **objects, const uint objects_len, const float co[2], UvNearestHit *hit)
 {
-  bool found = false;
-  for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
-    Object *obedit = objects[ob_index];
-    if (uv_find_nearest_face(scene, obedit, co, hit_final)) {
-      hit_final->ob = obedit;
-      found = true;
-    }
-  }
-  return found;
+  return uv_find_nearest_face_multi_ex(scene, objects, objects_len, co, hit, NULL);
 }
 
 static bool uv_nearest_between(const BMLoop *l, const float co[2], const int cd_loop_uv_offset)
@@ -830,8 +851,9 @@ bool uv_find_nearest_vert(
 
         hit->dist_sq = dist_test_sq;
 
-        hit->l = l;
+        hit->ob = obedit;
         hit->efa = efa;
+        hit->l = l;
         found = true;
       }
     }
@@ -845,13 +867,12 @@ bool uv_find_nearest_vert_multi(Scene *scene,
                                 const uint objects_len,
                                 float const co[2],
                                 const float penalty_dist,
-                                UvNearestHit *hit_final)
+                                UvNearestHit *hit)
 {
   bool found = false;
   for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
     Object *obedit = objects[ob_index];
-    if (uv_find_nearest_vert(scene, obedit, co, penalty_dist, hit_final)) {
-      hit_final->ob = obedit;
+    if (uv_find_nearest_vert(scene, obedit, co, penalty_dist, hit)) {
       found = true;
     }
   }
@@ -1298,7 +1319,7 @@ static int uv_select_edgering(
 static void uv_select_linked_multi(Scene *scene,
                                    Object **objects,
                                    const uint objects_len,
-                                   UvNearestHit *hit_final,
+                                   UvNearestHit *hit,
                                    const bool extend,
                                    bool deselect,
                                    const bool toggle,
@@ -1306,12 +1327,12 @@ static void uv_select_linked_multi(Scene *scene,
 {
   const bool uv_sync_select = (scene->toolsettings->uv_flag & UV_SYNC_SELECTION);
 
-  /* loop over objects, or just use hit_final->ob */
+  /* loop over objects, or just use hit->ob */
   for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
-    if (hit_final && ob_index != 0) {
+    if (hit && ob_index != 0) {
       break;
     }
-    Object *obedit = hit_final ? hit_final->ob : objects[ob_index];
+    Object *obedit = hit ? hit->ob : objects[ob_index];
 
     BMFace *efa;
     BMLoop *l;
@@ -1342,7 +1363,7 @@ static void uv_select_linked_multi(Scene *scene,
     stack = MEM_mallocN(sizeof(*stack) * (em->bm->totface + 1), "UvLinkStack");
     flag = MEM_callocN(sizeof(*flag) * em->bm->totface, "UvLinkFlag");
 
-    if (hit_final == NULL) {
+    if (hit == NULL) {
       /* Use existing selection */
       BM_ITER_MESH_INDEX (efa, &iter, em->bm, BM_FACES_OF_MESH, a) {
         if (uvedit_face_visible_test(scene, efa)) {
@@ -1399,7 +1420,7 @@ static void uv_select_linked_multi(Scene *scene,
     }
     else {
       BM_ITER_MESH_INDEX (efa, &iter, em->bm, BM_FACES_OF_MESH, a) {
-        if (efa == hit_final->efa) {
+        if (efa == hit->efa) {
           stack[stacksize] = a;
           stacksize++;
           flag[a] = 1;
@@ -1941,8 +1962,14 @@ static int uv_mouse_select_multi(bContext *C,
   }
   else if (selectmode == UV_SELECT_FACE) {
     /* find face */
-    found_item = uv_find_nearest_face_multi(scene, objects, objects_len, co, &hit);
+    UvNearestHit hit_in_face = UV_NEAREST_HIT_INIT_MAX(&region->v2d);
+    found_item = uv_find_nearest_face_multi_ex(
+        scene, objects, objects_len, co, &hit, &hit_in_face);
     if (found_item) {
+      if (hit.ob == NULL) {
+        hit = hit_in_face;
+        printf("Using hit in face\n");
+      }
       BMesh *bm = BKE_editmesh_from_object(hit.ob)->bm;
       BM_mesh_active_face_set(bm, hit.efa);
     }