Fix bug in how librt knob adapters handled edit_flag.

edit_flag identifies the exact primitive operation, while
edit_mode identifies the interaction class.

rt_knob_edit_rot/tran/sca() incorrectly replaced a
primitive-specific flag with the generic operation before
dispatching.

Fixed in src/librt/edit.cpp:811:

- Preserve primitive-specific edit_flag when edit_mode matches.
- Fall back to generic operations otherwise.
- Covers translation, rotation, and scale paths.

The MGED faceplate and constrained-axis handlers already
preserve the flag correctly; they route through these adapters.

Added regressions in src/librt/tests/edit/arb8.cpp:312 for:

- ARB5 point 5 direct editing.
- ARB5 point 5 knob dragging.
- ARB face rotation through the knob path.

include/rt/edit.h

@@ -473,6 +473,12 @@ rt_edit_knob_cmd_process(
         char origin, int incr_flag, void *u_data
 	);
 
+/* Knob operations preserve a primitive-specific edit_flag when edit_mode
+ * already matches the requested interaction class.  This allows interactive
+ * drags to continue operations such as moving an ARB vertex or rotating an
+ * ARB face; generic RT_PARAMS_EDIT_* flags are selected only when the current
+ * edit is not in the corresponding class. */
+
 RT_EXPORT extern void
 rt_knob_edit_rot(struct rt_edit *s,
         char coords,

src/librt/edit.cpp

@@ -808,6 +808,19 @@ rt_edit_knob_cmd_process(
     return BRLCAD_ERROR;
 }
 
+/*
+ * Knob input describes an interaction class, but the active edit flag may
+ * identify a primitive-specific operation in that class.  Keep that exact
+ * operation selected when the caller has already supplied a matching
+ * edit_mode; otherwise fall back to the generic operation.
+ */
+static void
+rt_edit_set_knob_edflag(struct rt_edit *s, int edit_mode)
+{
+    if (s->edit_mode != edit_mode)
+	rt_edit_set_edflag(s, edit_mode);
+}
+
 void
 rt_knob_edit_rot(struct rt_edit *s,
 	char coords,
@@ -853,7 +866,7 @@ rt_knob_edit_rot(struct rt_edit *s,
 	int save_edflag = s->edit_flag;
 	int save_mode = s->edit_mode;
 
-	rt_edit_set_edflag(s, RT_PARAMS_EDIT_ROT);
+	rt_edit_set_knob_edflag(s, RT_PARAMS_EDIT_ROT);
 
 	rt_edit_process(s);
 
@@ -952,7 +965,7 @@ rt_knob_edit_tran(struct rt_edit *s,
 	int save_edflag = s->edit_flag;
 	int save_mode = s->edit_mode;
 
-	rt_edit_set_edflag(s, RT_PARAMS_EDIT_TRANS);
+	rt_edit_set_knob_edflag(s, RT_PARAMS_EDIT_TRANS);
 
 	VADD2(s->e_para, delta, s->curr_e_axes_pos);
 	s->e_inpara = 3;
@@ -996,7 +1009,7 @@ rt_knob_edit_sca(struct rt_edit *s, int matrix_edit)
 	int save_edflag = s->edit_flag;
 	int save_mode = s->edit_mode;
 
-	rt_edit_set_edflag(s, RT_PARAMS_EDIT_SCALE);
+	rt_edit_set_knob_edflag(s, RT_PARAMS_EDIT_SCALE);
 
 	rt_edit_process(s);
 

src/librt/tests/edit/arb8.cpp

@@ -124,6 +124,30 @@ arb8_reset(struct rt_edit *s, struct rt_arb_internal *arb, struct rt_arb8_edit *
     s->mv_context = 1;
 }
 
+static void
+arb5_reset(struct rt_edit *s, struct rt_arb_internal *arb, struct rt_arb8_edit *a)
+{
+    VSET(arb->pt[0], 0, 0, 0);
+    VSET(arb->pt[1], 1, 0, 0);
+    VSET(arb->pt[2], 1, 1, 0);
+    VSET(arb->pt[3], 0, 1, 0);
+    VSET(arb->pt[4], 0.5, 0.5, 1);
+    VMOVE(arb->pt[5], arb->pt[4]);
+    VMOVE(arb->pt[6], arb->pt[4]);
+    VMOVE(arb->pt[7], arb->pt[4]);
+
+    a->newedge = 0;
+    a->edit_menu = 0;
+
+    VSETALL(s->e_keypoint, 0.0);
+    MAT_IDN(s->acc_rot_sol);
+    MAT_IDN(s->incr_change);
+    s->acc_sc_sol = 1.0;
+    s->e_inpara = 0;
+    s->es_scale   = 0.0;
+    s->mv_context = 1;
+}
+
 
 int
 main(int argc, char *argv[])
@@ -285,6 +309,52 @@ main(int argc, char *argv[])
 	bu_exit(1, "ERROR: RT_PARAMS_EDIT_ROT(xy) failed\n");
     bu_log("RT_PARAMS_EDIT_ROT(xy) SUCCESS: rotation applied via knob path\n");
 
+    /* ================================================================
+     * PTARB ARB5 point 5: both direct parameters and knob translation must
+     * retain the primitive-specific edit flag.  Point 5 is stored at pt[4]
+     * and duplicated in pt[5..7].
+     * ================================================================*/
+    arb5_reset(s, arb, a);
+    a->edit_menu = 8;  /* symbolic ARB5 point-5 menu argument */
+    rt_edit_set_edflag(s, PTARB);
+    s->edit_mode = RT_PARAMS_EDIT_TRANS;
+    s->e_inpara = 3;
+    VSET(s->e_para, 0.75, 0.75, 1.25);
+    s->mv_context = 0;
+    rt_edit_process(s);
+    {
+	point_t expected = {0.75, 0.75, 1.25};
+	point_t expected_base = {0, 0, 0};
+	if (!VNEAR_EQUAL(arb->pt[4], expected, VUNITIZE_TOL) ||
+	    !VNEAR_EQUAL(arb->pt[5], expected, VUNITIZE_TOL) ||
+	    !VNEAR_EQUAL(arb->pt[6], expected, VUNITIZE_TOL) ||
+	    !VNEAR_EQUAL(arb->pt[7], expected, VUNITIZE_TOL))
+	    bu_exit(1, "ERROR: PTARB ARB5 point 5 parameter edit failed\n");
+	if (!VNEAR_EQUAL(arb->pt[0], expected_base, VUNITIZE_TOL))
+	    bu_exit(1, "ERROR: PTARB ARB5 point 5 moved the base\n");
+	bu_log("PTARB ARB5 point 5 parameter edit SUCCESS\n");
+    }
+
+    arb5_reset(s, arb, a);
+    a->edit_menu = 8;
+    rt_edit_set_edflag(s, PTARB);
+    s->edit_mode = RT_PARAMS_EDIT_TRANS;
+    s->mv_context = 0;
+    VMOVE(s->curr_e_axes_pos, arb->pt[4]);
+    vect_t point_delta = {0.1, 0.2, 0.3};
+    rt_knob_edit_tran(s, 'm', 0, point_delta);
+    {
+	point_t expected = {0.6, 0.7, 1.3};
+	point_t expected_base = {0, 0, 0};
+	if (!VNEAR_EQUAL(arb->pt[4], expected, VUNITIZE_TOL) ||
+	    !VNEAR_EQUAL(arb->pt[5], expected, VUNITIZE_TOL) ||
+	    !VNEAR_EQUAL(arb->pt[6], expected, VUNITIZE_TOL) ||
+	    !VNEAR_EQUAL(arb->pt[7], expected, VUNITIZE_TOL) ||
+	    !VNEAR_EQUAL(arb->pt[0], expected_base, VUNITIZE_TOL))
+	    bu_exit(1, "ERROR: PTARB ARB5 point 5 knob edit failed\n");
+	bu_log("PTARB ARB5 point 5 knob edit SUCCESS\n");
+    }
+
 
     /* ================================================================
      * RT_MATRIX_EDIT_ROT: absolute matrix rotation from keyboard angles
@@ -465,6 +535,25 @@ bu_log("RT_MATRIX_EDIT_TRANS_MODEL_XYZ SUCCESS: "
 	   a->es_peqn[a->edit_menu][0], a->es_peqn[a->edit_menu][1],
 	   a->es_peqn[a->edit_menu][2], a->es_peqn[a->edit_menu][W]);
 
+    /* The same face operation must survive the interactive rotation knob
+     * adapter, which supplies an incremental matrix rather than parameters.
+     */
+    arb8_reset(s, arb, a);
+    a->edit_menu = 4;
+    s->e_inpara = 1;
+    s->e_para[0] = 1.0;
+    rt_edit_set_edflag(s, ECMD_ARB_SETUP_ROTFACE);
+    rt_edit_process(s);
+    plane_t knob_orig_peqn;
+    HMOVE(knob_orig_peqn, a->es_peqn[a->edit_menu]);
+    mat_t knob_rot;
+    MAT_IDN(knob_rot);
+    bn_mat_angles(knob_rot, 45.0, 0.0, 0.0);
+    rt_knob_edit_rot(s, 'm', 'm', 0, knob_rot);
+    if (VEQUAL(a->es_peqn[a->edit_menu], knob_orig_peqn))
+	bu_exit(1, "ERROR: ECMD_ARB_ROTATE_FACE knob edit did not rotate face\n");
+    bu_log("ECMD_ARB_ROTATE_FACE knob edit SUCCESS\n");
+
     rt_edit_destroy(s);
     db_close(dbip);
     return 0;