Fix T98552: Experimental Tweak Select: Curve handle tweak is difficult

When this preference is enabled, use selection behavior matching the
graph editor. We may want to make this default (see T98552).

4 files changed, 50 insertions, 8 deletions

diff --git a/source/blender/editors/curve/editcurve.c b/source/blender/editors/curve/editcurve.c
index 9da9845116d..dc49a5ed531 100644
--- a/source/blender/editors/curve/editcurve.c
+++ b/source/blender/editors/curve/editcurve.c
@@ -4729,6 +4729,7 @@ void CURVE_OT_make_segment(wmOperatorType *ot)
 bool ED_curve_editnurb_select_pick(bContext *C,
                                    const int mval[2],
                                    const int dist_px,
+                                   const bool vert_without_handles,
                                    const struct SelectPick_Params *params)
 {
   Depsgraph *depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
@@ -4744,6 +4745,9 @@ bool ED_curve_editnurb_select_pick(bContext *C,
   ED_view3d_viewcontext_init(C, &vc, depsgraph);
   copy_v2_v2_int(vc.mval, mval);
 
+  const bool use_handle_select = vert_without_handles &&
+                                 (vc.v3d->overlay.handle_display != CURVE_HANDLE_NONE);
+
   bool found = ED_curve_pick_vert_ex(&vc, 1, dist_px, &nu, &bezt, &bp, &hand, &basact);
 
   if (params->sel_op == SEL_OP_SET) {
@@ -4779,7 +4783,12 @@ bool ED_curve_editnurb_select_pick(bContext *C,
       case SEL_OP_ADD: {
         if (bezt) {
           if (hand == 1) {
-            select_beztriple(bezt, SELECT, SELECT, HIDDEN);
+            if (use_handle_select) {
+              bezt->f2 |= SELECT;
+            }
+            else {
+              select_beztriple(bezt, SELECT, SELECT, HIDDEN);
+            }
           }
           else {
             if (hand == 0) {
@@ -4800,7 +4809,12 @@ bool ED_curve_editnurb_select_pick(bContext *C,
       case SEL_OP_SUB: {
         if (bezt) {
           if (hand == 1) {
-            select_beztriple(bezt, DESELECT, SELECT, HIDDEN);
+            if (use_handle_select) {
+              bezt->f2 &= ~SELECT;
+            }
+            else {
+              select_beztriple(bezt, DESELECT, SELECT, HIDDEN);
+            }
             if (bezt == vert) {
               cu->actvert = CU_ACT_NONE;
             }
@@ -4824,13 +4838,23 @@ bool ED_curve_editnurb_select_pick(bContext *C,
         if (bezt) {
           if (hand == 1) {
             if (bezt->f2 & SELECT) {
-              select_beztriple(bezt, DESELECT, SELECT, HIDDEN);
+              if (use_handle_select) {
+                bezt->f2 &= ~SELECT;
+              }
+              else {
+                select_beztriple(bezt, DESELECT, SELECT, HIDDEN);
+              }
               if (bezt == vert) {
                 cu->actvert = CU_ACT_NONE;
               }
             }
             else {
-              select_beztriple(bezt, SELECT, SELECT, HIDDEN);
+              if (use_handle_select) {
+                bezt->f2 |= SELECT;
+              }
+              else {
+                select_beztriple(bezt, SELECT, SELECT, HIDDEN);
+              }
               BKE_curve_nurb_vert_active_set(cu, nu, bezt);
             }
           }
@@ -4861,7 +4885,12 @@ bool ED_curve_editnurb_select_pick(bContext *C,
         if (bezt) {
 
           if (hand == 1) {
-            select_beztriple(bezt, SELECT, SELECT, HIDDEN);
+            if (use_handle_select) {
+              bezt->f2 |= SELECT;
+            }
+            else {
+              select_beztriple(bezt, SELECT, SELECT, HIDDEN);
+            }
           }
           else {
             if (hand == 0) {
diff --git a/source/blender/editors/curve/editcurve_pen.c b/source/blender/editors/curve/editcurve_pen.c
index fca850076ae..a98b165e99d 100644
--- a/source/blender/editors/curve/editcurve_pen.c
+++ b/source/blender/editors/curve/editcurve_pen.c
@@ -1655,7 +1655,7 @@ static int curve_pen_modal(bContext *C, wmOperator *op, const wmEvent *event)
   else if (ELEM(event->type, LEFTMOUSE)) {
     if (ELEM(event->val, KM_RELEASE, KM_DBL_CLICK)) {
       if (delete_point && !cpd->new_point && !cpd->dragging) {
-        if (ED_curve_editnurb_select_pick(C, event->mval, threshold_dist_px, &params)) {
+        if (ED_curve_editnurb_select_pick(C, event->mval, threshold_dist_px, false, &params)) {
           cpd->acted = delete_point_under_mouse(&vc, event);
         }
       }
@@ -1714,7 +1714,7 @@ static int curve_pen_modal(bContext *C, wmOperator *op, const wmEvent *event)
           }
         }
         else if (select_point) {
-          ED_curve_editnurb_select_pick(C, event->mval, threshold_dist_px, &params);
+          ED_curve_editnurb_select_pick(C, event->mval, threshold_dist_px, false, &params);
         }
       }
 
diff --git a/source/blender/editors/include/ED_curve.h b/source/blender/editors/include/ED_curve.h
index 9f4833bf1d7..061b783797d 100644
--- a/source/blender/editors/include/ED_curve.h
+++ b/source/blender/editors/include/ED_curve.h
@@ -49,10 +49,12 @@ void ED_curve_editnurb_free(struct Object *obedit);
 
 /**
  * \param dist_px: Maximum distance to pick (in pixels).
+ * \param vert_without_handles: When true, selecting the knot doesn't select the handles.
  */
 bool ED_curve_editnurb_select_pick(struct bContext *C,
                                    const int mval[2],
                                    int dist_px,
+                                   bool vert_without_handles,
                                    const struct SelectPick_Params *params);
 
 struct Nurb *ED_curve_add_nurbs_primitive(
diff --git a/source/blender/editors/space_view3d/view3d_select.c b/source/blender/editors/space_view3d/view3d_select.c
index efe89621e7b..fc817b43a8b 100644
--- a/source/blender/editors/space_view3d/view3d_select.c
+++ b/source/blender/editors/space_view3d/view3d_select.c
@@ -2878,6 +2878,7 @@ static int view3d_select_exec(bContext *C, wmOperator *op)
   struct SelectPick_Params params = {0};
   ED_select_pick_params_from_operator(op->ptr, &params);
 
+  const bool vert_without_handles = RNA_boolean_get(op->ptr, "vert_without_handles");
   bool center = RNA_boolean_get(op->ptr, "center");
   bool enumerate = RNA_boolean_get(op->ptr, "enumerate");
   /* Only force object select for edit-mode to support vertex parenting,
@@ -2932,7 +2933,8 @@ static int view3d_select_exec(bContext *C, wmOperator *op)
       changed = ED_lattice_select_pick(C, mval, &params);
     }
     else if (ELEM(obedit->type, OB_CURVES_LEGACY, OB_SURF)) {
-      changed = ED_curve_editnurb_select_pick(C, mval, ED_view3d_select_dist_px(), &params);
+      changed = ED_curve_editnurb_select_pick(
+          C, mval, ED_view3d_select_dist_px(), vert_without_handles, &params);
     }
     else if (obedit->type == OB_MBALL) {
       changed = ED_mball_select_pick(C, mval, &params);
@@ -3009,6 +3011,15 @@ void VIEW3D_OT_select(wmOperatorType *ot)
   prop = RNA_def_boolean(ot->srna, "object", 0, "Object", "Use object selection (edit mode only)");
   RNA_def_property_flag(prop, PROP_SKIP_SAVE);
 
+  /* Needed for select-through to usefully drag handles, see: T98254.
+   * NOTE: this option may be removed and become default behavior, see design task: T98552. */
+  prop = RNA_def_boolean(ot->srna,
+                         "vert_without_handles",
+                         0,
+                         "Control Point Without Handles",
+                         "Only select the curve control point, not it's handles");
+  RNA_def_property_flag(prop, PROP_SKIP_SAVE);
+
   prop = RNA_def_int_vector(ot->srna,
                             "location",
                             2,